KR20050007190A - Solution deposition of chalcogenide films - Google Patents

Abstract

PURPOSE: To provide a method for depositing a film of metal chalcogenide to prepare a film of a metal chalcogenide semiconducting material having an advantage of being low cost, a method for a separated hydrazinium-based precursor of metal chalcogenide, and a field-effect thin film transistor device including the metal chalcogenide as a channel layer. CONSTITUTION: The method for depositing a film of metal chalcogenide comprises a step of forming a complex solution of the precursor by contacting a separated hydrazinium-based precursor of metal chalcogenide with a solvent in which a soluble additive is retained; a step of coating the complex solution on a substrate so that a coating of the solution is formed on the substrate; a step of forming a film of the complex on the substrate by removing the solvent from the coating; and a step of annealing the complex film so that a metal chalcogenide film is formed on the substrate. The method for preparing a separated hydrazinium-based precursor of metal chalcogenide comprises a step of preparing an ammonium-based precursor of the metal chalcogenides by contacting one or more metal chalcogenides, an amine compound represented by the following formula: NR¬5R¬6R¬7, wherein each of R¬5, R¬6 and R¬7 is independently selected from the group consisting of hydrogen, aryl, methyl, ethyl and linear, branched or cyclic alkyl having 3 to 6 carbon atoms, and a salt of H2S, H2Se or H2Te; a step of preparing a solution of hydrazinium-based precursor of the metal chalcogenides by contacting the ammonium-based precursor of the metal chalcogenides, a hydrazine compound represented by the following formula: R¬1R¬2N-NR¬3R¬4, wherein each of R¬1, R¬2, R¬3 and R¬4 is independently selected from the group consisting of hydrogen, aryl, methyl, ethyl and linear, branched or cyclic alkyl having 3 to 6 carbon atoms, and optionally, an elemental chalcogen selected from the group consisting of S, Se, Te and a combination thereof; and a step of separating the hydrazinium-based precursor of the metal chalcogenides into a substantially pure product.

Description

SOLUTION DEPOSITION OF CHALCOGENIDE FILMS

Field of invention

The present invention relates to a method of depositing a film of metal chalcogenide from a solution, and to a method of manufacturing a field-effect transistor comprising the film. More specifically, the present invention relates to a method of manufacturing a field effect transistor comprising a film of metal chalcogenide deposited from a solution as a channel layer.

Description of the prior art

The ability to deposit high quality semiconducting, metal and insulating thin films forms one of the important pillars of today's solid state electronics. The solar cell may include a thin n-type semiconductor layer (˜0.25 μm) deposited on a p-type substrate, for example, with electrical contacts attached to each layer to accumulate photocurrent. . Light-emitting diodes (LED's) typically consist of a p-n bilayer, which emits light under suitable forward bias conditions.

Thin film field effect transistors, referred to herein as TFT's, comprise a thin p-type or n-type semiconducting channel layer, wherein conductivity is applied by applying a bias voltage to a conductive gate layer separated from the channel by a thin insulating isolation layer. Adjusted. Electronic materials comprising modern semiconducting Divas typically have silicon as their main component, but the same can be considered from other classes of materials, which in some cases potentially offer advantages over silicon-based technology.

Thin film field effect transistors (TFT's) are most widely used as exchange elements in electronic and display applications, most notably for logic and driver circuitry within processors. Currently, for many low-bandwidth applications, including those used in active matrix liquid crystal displays, TFT's are manufactured using amorphous silicon as the semiconductor. Amorphous silicon provides a cheaper alternative to crystalline silicon as an essential condition to reduce the cost of transistors for large area applications. However, the use of amorphous silicon is limited to slower speed devices because the mobility (˜10 ⁻¹ cm ² / V-sec) is about 15,000 times smaller than that of crystalline silicon.

In addition, although amorphous silicon is cheaper to deposit than crystalline silicon, deposition of amorphous silicon still requires expensive processes such as plasma enhanced chemical vapor deposition. Therefore, research into alternative semiconductors (i.e., non-silicon) for use in TFT's and other electronic devices is being actively conducted.

If one can identify semiconducting materials that simultaneously provide higher transfer rates and lower cost processing at moderate temperatures / low temperatures, these materials can be fabricated on plastics, including lightweight, flexible and very large displays or electronics. Many new uses can be planned.

Recently, organic semiconductors have been assigned to TFT's [e.g., US Pat. No. 5,347,144 (Garnier et.al.) entitled "Thin-Layer Field Effect Transistor With MIS Structure Whose Insulator and Semiconductor Are Made of Organic Materials." ) And LED's [e.g. SE Shaheen et al., "Organic Light-Emitting Diode with 20 lm / W Efficiency Using a Triphenyldiamine Side-Group Polymer as the Hole Transport Layer", Appl. Phys. Lett. 74, 3212 (1999), which is of considerable interest as a potential substitute for weapon counterparts.

Organic materials have the advantage of simple low temperature thin film processing through inexpensive techniques such as spin coating, ink jet printing, thermal evaporation or stamping. Over the last few years, the carrier mobility of organic channel layers in OTFTs (organic TFTs) has increased significantly from <10 ^-4 cm ² / V-sec to -1 cm ² / V-sec [relative to amorphous silicon] [ See, for example, CD Dimitrakopoulos and DJ Mascaro, "Organic Thin-filmtransistors: A review of recent advances", IBM J. Res & Dev. 45, 11-27 (2001).

Although very promising in terms of processing, cost and weight considerations, organic compounds generally have a number of disadvantages, including poor thermal and mechanical stability. In addition, although electromigration in organic materials has improved significantly over the last 15 years, the rate of transport is basically organic molecules (as opposed to the stronger covalent and ionic binding forces found in a wide range of inorganic systems). Limited by weak van der Waals interactions of the liver.

The bounded inherent upper limit for the rate of electrophoresis translates into the highest in exchange rate, and therefore translates into the highest in the range of applications where low cost organic devices can be used. Therefore, organic semiconductors are mainly considered for low band applications.

One approach that can improve transfer rate / durability involves combining the processability of organic materials and the desired electrophoretic and thermal / mechanical properties of inorganic semiconductors in hybrid systems [D.B. Mitzi et al., "Organic-Inorganic Electronics", IBM J. Res & Dev. 45, 29-45 (2001). Recently, organic-inorganic hybrid membranes include TFTs (see, for example, US Pat. No. 6,180,956 to Chondroudis et al., Entitled "Thin-Film Transistors with Organic-Inorganic Hybrid Materials as Semiconducting Channels") and Anti-electric devices, including LEDs (see, for example, US Pat. No. 6,420,056 (assigned to Chondroudis et al.) Entitled "Electroluminescent Device With Dye-Containing Organic-Inorganic Hybrid Materials as an Emitting Layer"). It is used as a conductive element.

Several simple techniques have been described for depositing crystalline organic-inorganic hybrid films, including multi-source thermal evaporation, single-source thermal ablation, and melt processing.

In addition, solution-deposition techniques (e.g., spin coating, stamping, and printing) have also received recent attention, and these techniques have enabled the rapid and inexpensive deposition of hybrids on various arrays of substrates. Because it is particularly attractive. TFT's, based on spin-coated semiconducting tin iodide based hybrids, produce a transfer rate as high as 1 cm ² / V-sec (similar to the best organic devices fabricated using vapor deposition and amorphous silicon). .

Melt-processing of hybrid systems improves the particle structure of the semiconducting membranes, leading to higher migration rates of 2-3 cm ² / V-sec [DB Mitzi et al., “Hybrid Field-Effect Transistors Based on a Low- Temperature Melt-Processed Channel Layer ", Adv. Mater. 14, 1772-1776 (2002).

Although very promising, current examples of hybrid semiconductors are based on a wide range of metal halide backbones (eg metal chlorides, metal bromide, metal iodides, most commonly tin iodide). Metal halides are relatively ionic in nature, limiting the choice of possible semiconducting systems with the potential for high migration rates. In addition, especially tin (II) iodide systems are very sensitive to air, so all processing must be carried out under inert atmospheric conditions. Moreover, although tin (II) iodide based systems are p-type semiconductors, it is also desirable to look for examples of n-type systems that allow easy application by complementary logic. Nothing has been confirmed to date.

Another alternative to silicon, organic and metal halide based hybrid semiconductors is metal chalcogenides (eg metal sulfides, metal selenides, metal tellurides) as semiconducting elements for use in TFT's and other electronic devices. Entails using. Early solar cells [DC Raynolds et al., "Photovoltaic Effect in Cadmium Sulfide", Phy. Rev. 96, 533 (1954) and TFTs [PK Weimer, "The TFT-A New Thin-Film Transistor", Proc. IRE 50, 1462-1469 (1964), was based on the actual metal chalcogenide active layer. There are many examples of metal chalcogenide systems that are potentially useful as semiconducting materials. Tin sulfide (II), SnS _2, is a candidate material that has generated considerable interest as a semiconducting material for solar cells, with n-type conductivity, optical band gap ˜2.1 eV and reported migration rate of 18 cm ² / V-sec [ G. Domingo et al., Fundamental Optical Absorption in SnS ₂ and SnSe ₂ ”, Phys. Rev. 143, 536-541 (1966)].

Such systems are expected to produce higher transfer rates than organic and metal halide based hybrids as a result of the stronger covalent nature of chalcogenides and also provide additional opportunities for identifying n-type semiconductors.

Reported migration rates of metal chalcogenides are described, for example, in SnSe ₂ (27 cm ² / V-sec / n-type) [G. Domingo et al., "Fundamental Optical Absorption in SnS ₂ and SnSe ₂ ", Phys. Rev. 143, 536-541 (1996)], SnS ₂ (18 cm ² / V-sec / n-type) [T. Shibata et al., "Electrical Charaterization of 2H-SnS ₂ Single Crystals Synthesized by the Low Temperature Chemical Vapor Transport Method", J. Phys. Chem. Solids 52, 551-553 (1991)], CdS (340 cm ² / V-sec / n-type), CdSe (800 cm ² / V-sec / n-type) [SM Sze, "Physics of Semiconductor Devices" , John Willey & Sons, New York, 1981, p. 849], ZnSe (600 cm ² / V-sec / n-type), and ZnTe (100 cm ² / V-sec / p-type) [BG Streetman, "Solid State Electronic Devices", Prentice-Hall, Inc. , New Jerey, 1980, p. 443].

While the potential for higher transfer rates exists, the increased covalent bonding of a wide range of metal chalcogenide systems also reduces their solubility and increases the melting temperature, which is important for simple low cost thin film deposition techniques for such systems. Cause.

Thermal evaporation [A. Van Calster et al., "Polycrystalline cadmium selenide films for thin film transistors". J. Crystal Growth 86, 924-928 (1998), Chemical Vapor Deposition (CVD) [LS Price et al., “Atmospheric Pressure CVD of SnS and SnS ₂ on Glass”, Adv. Mater. 10, 222-225 (1998)], galvanic deposition (BE McCandless et al., "Galvanic Deposition of Cadmium Sulfide Thin Films.", Solar Energy Materials and Solar Cells 36, 369-379 (1995)), chemical bath deposition ( chemical bath deposition (FY Gan et al., "Preparation of Thin-Film Trnnsistors With Chemical Bath Deposited CdSe and CdS Thin Films", IEEE Transactions on Electron Devices 49, 15-18 (2002)), and continuous ion layer adsorption and SILAR [BR Sankapal et al., "Successive ionic layer adsorption and reaction (SILAR) method for the deposition of large area (~ 10 cm ² ) tin disufide (SnS ₂ ) thin films", Mater. Res. Bull. 35, 2027-2035 (2001), have been proposed and used for the deposition of chalcogenide-based films.

However, these techniques are generally not modifiable with low cost, high throughput (rapid) solution based deposition techniques such as spin coating, printing and stamping. What is needed for the application of high throughput techniques is the practically soluble precursor to the chalcogenide and a suitable solvent. The potential for high electrophoretic rates in metal chalcogenide systems and n-type and p-type channel devices has led to the low cost solution based deposition in the field of electronics, where easy rapid solution-based techniques are currently being performed primarily in organic electronics environments. If it can be identified, it can be extended to high priced applications such as logic circuits and very large area displays.

Spray pyrolysis is one technique that utilizes rapid decomposition of soluble precursors [M. Krunks et al., "Composition of CuInS ₂ thin films prepared by spray pyrolysis", Thin Solid Films 403-404, 71-75 (2002). This technique involves spraying a solution containing chloride salts of metals with a source of chalcogen (eg, SC (NH ₂ ) ₂ ) onto a heated substrate (typically in the range of 250-450 ° C.) do.

Although chalcogenide membranes are formed using this technique, the membranes generally have significant impurities of halogen, carbon or nitrogen. While reducing the atmosphere of H ₂ or H ₂ S at temperatures below 450 ° C., annealing may be used to reduce the level of impurities in the film, but such relatively aggressive treatment is incompatible with a wide range of substrate materials, and / or Requires special equipment.

See B.A. Ridley et al., "All-Inorganic Field Effect Transistors Frabricated by Printing", Science 286, 746-749 (1999), print using soluble metal chalcogenide precursors formed using organic deactivated CdSe nanocrystals. A CdSe semiconducting film is described. However, this technique requires the formation of nanocrystals that are carried out under tight control over the particle size distribution to enable effective sintering during post-deposition heat treatment. Particle size control requires repeated dissolution steps and centrifugation steps to isolate a properly uniform collection of nanocrystals.

In addition, reported TFT devices fabricated using this technique include substantial device hysteresis and negative resistance in saturation regions, presumably as a result of traps or interface states within the semiconducting film and at the interface between the semiconductor and the insulator. Unique properties.

In addition, S. Dhingra et al., "The use of soluble metal-polyselenide complexes an precursors to binary and ternary solid metal selenides", Mat. Res. Soc. Symp. Proc. 180, 825-830 (1990) demonstrates soluble precursors for metal chalcogenides that can be used to heat the decomposition of the precursors and then rotate the coat film of the corresponding metal chalcogenides.

In this process, however, the species used to dissolve the chalcogenide backbone (ie, quaternary ammonium or phosphonium polyselenide), which is finally degraded from the sample during thermal treatment, is very bulky and contains most of the membrane (eg 70-87%) disappears during the annealing treatment sequence. This formed film results in inferior connectivity and quality.

The large percentage of samples lost during heat treatment is likely to be discontinuous because the thin film (which is considered to be a film with a thickness of ~ 25-35 μm in the above-mentioned studies) tends to be discontinuous, so only relatively thick films are deposited using this technique. It can be. In addition, relatively high temperatures are required for the thermal decomposition of polyselenide, which allows even the most thermally strong plastic substrates (e.g., Kapton sheets can withstand temperatures as high as 400 ° C). Makes it incompatible

In addition, according to the conclusion of one study, crystalline MoS ₂ membranes can be spin coated from a solution of (NH ₄ ) ₂ MoS ₄ in organic diamine [J. Putz and MA Aegerter, "Spin-Coating of MoS ₂ Thin Films", Pro. of International Congress on Glass, vol. 18, San Francisco, CA, July 5-10, 1998, 1675-1680. However, a high temperature annealing treatment after deposition is necessary to achieve a crystalline film (600-800 ° C.), which renders the process incompatible with organic flexible substrate materials.

Similar procedures led to the formation of amorphous As ₂ S ₃ and As ₂ Se ₃ membranes [GC Chern and I. Lauks, “Spin-Coated Amorphous Chalcogenide Films”, J. Applied Phys. 53, 6979-6982 (1982)], attempts to deposit other main-group metal chalcogenides such as Sb ₂ S ₃ and GeS _x have not been successful because of the low solubility of the precursors in diamine solvents. [J. Putz and MA Aegerter, "Spin-Coating of MoS ₂ Thin Films", Proc. of International Congress on Glass, vol. 18, San Francisco, CA, July 5-10, 1998, 1675-1680.

Therefore, improved processes of the above-mentioned solution-based processes are necessary for practical use, in particular for the preparation of crystalline films of main group metal chalcogenides, such as those derived from Ge, Sn, Pb, Sb, Bi Ga, In, Tl. In addition, it is possible to provide a high transfer rate in the semiconductor having a band gap suitable for the transistor.

The present invention provides hydrazinium metal chalcogenides represented by the formula:

M _z X _q (R ¹ R ² N-NHR ³ R ⁴ ) _{2q- nz} (R ¹ R ² N-NR ³ R ⁴ ) _m

In the above formula, M is a main group metal having valency n, and n is an integer of 1 to 6; X is a chalcogen; z is an integer from 1 to 10; q is an integer from 1 to 30; m is 1 to 30.5; Each R ¹ , R ² , R ³ and R ⁴ is independently selected from hydrogen, aryl, methyl, ethyl and linear, branched or cyclic (C ₃ -C ₆ ) alkyl.

The present invention also provides a method of depositing a film of metal chalcogenide. The method comprises contacting a separate hydrazinium precursor of a metal chalcogenide and a solvent having a solubilizing additive therein to form a complex solution of the precursor; Applying a complex solution onto the substrate to form a coating of the solution on the substrate; Removing the solvent from the coating to produce a film of the complex on the substrate; And then annealing the complex film to decompose the complex to produce a metal chalcogenide film on the substrate.

The present invention also relates to a source region and a drain region, a channel layer extending between the source region and the drain region and comprising a semiconductive material, a gate region disposed to be spaced apart adjacent to the channel layer, the gate region and the source region. , A method of manufacturing a field effect transistor of a type having an electrically insulating layer between a drain region and a channel layer, the method comprising

Contacting the separated hydrazinium precursor of the metal chalcogenide and a solvent having a solubilizing additive therein to form a complex solution of the precursor; Applying a complex solution onto the substrate to form a coating of the solution on the substrate; Removing the solvent from the coating to produce a film of the complex on the substrate; And subsequently producing a channel layer comprising a film of metal chalcogenide semiconducting material prepared by a process comprising annealing the complex film to decompose the complex to produce a metal chalcogenide film on the substrate. .

The present invention also provides a first method of preparing an isolated hydrazinium precursor of a metal chalcogenide. The first method comprises one or more metal chalcogenides, of formula R ¹ R ² N-NR ³ R ⁴ , wherein each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl And selected from linear, branched or cyclic (C ₃ -C ₆ ) alkyl], and the metal knife in the hydrazine compound by contacting an elemental chalcogen selected from S, Se, Te or a combination thereof. Producing a solution of hydrazinium precursor of cogenide; And separating the hydrazinium precursor of the metal chalcogenide as a substantially pure product.

The present invention also provides a second method of preparing an isolated hydrazinium precursor of a metal chalcogenide. The second process comprises one or more metal chalcogenides and the formulas NR ⁵ R ⁶ R ^{7 wherein} each R ⁵ , R ⁶ and R ⁷ is independently hydrogen, aryl, methyl, ethyl and linear, branched or ring Contacting an amine compound represented by type (C ₃ -C ₆ ) alkyl] with a salt of H ₂ S, H ₂ Se or H ₂ Te to generate an ammonium precursor of the metal chalcogenide; Ammonium-based precursors of metal chalcogenides, of formula R ¹ R ² N-NR ³ R ⁴ , wherein each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl and linear Selected from branched or cyclic (C ₃ -C ₆ ) alkyl], and the metal chalcogenide in the hydrazine compound by contacting an element chalcogen selected from S, Se, Te or a combination thereof. Generating a solution of a hydrazinium precursor; And separating the hydrazinium precursor of the metal chalcogenide as a substantially pure product.

Hydrazinium metal chalcogenides according to the invention can be prepared as separated products in substantially pure form by the first or second method described above.

Membranes prepared according to the invention have the advantage of low cost. Devices that use metal chalcogenide semiconducting materials as the channel layer produce the highest rates of transport currently reported for n-type spin coated devices.

Device features are also described in B.A. Ridley et al., “All-Inorganic Field Effect Transistors Fabricated by Printing”, Science 286, 746-749 (1999), perform better than CdSe semiconducting membranes in which the organically induced CdSe nano Print using soluble metal chalcogenide precursors formed by the use of crystals.

An important advantage of this method of the present invention is that the steps for forming the soluble hydrazinium-based precursor are performed separately from the solution processing of the thin film, so that the chemical company can manufacture the hydrazinium precursor and the device manufacturer can rotate the membrane. Due to the fact that it can. Thus, chemical companies are equipped with equipment to handle toxic and reactive hydrazines and hydrazine derivatives in their plants, making it possible to produce hydrazinium precursors more efficiently. Thus, device manufacturers can use less toxic solvents in their manufacturing plants to purchase precursors on demand and rotate the membrane.

The present invention also provides two alternative methods (method 1 and method 2) for solution deposition of chalcogenide films, in which one or more metal chalcogenides and hydrazine compounds are used to hydride the metal chalcogenides. A solution of nium based precursor is formed. In these alternative methods hydrazinium precursors are not isolated but are instead formed using hydrazinium compounds which act as solvents in situ.

Low cost metal chalcogenide semiconducting materials made in accordance with some methods of the present invention can be used in flat panel displays, nonlinear optical / photoconductive devices, chemical sensors, light emitting and light transfer layers in light emitting diodes, thin film transistors, and field effect transistors. It can be used for a variety of applications, including channel layers, and optical data storage media including optical data storage phase change media.

FIG. 1 shows a thermogravimetric analysis (TGA) scan of hydrazium tin sulfide (IV) precursor.

FIG. 2 shows an X-ray diffraction pattern of a tin sulfide (IV) film deposited by Method 1 using spin coating.

FIG. 3 shows the X-ray crystal structure of (N ₂ H ₄ ) ₃ (N ₂ H ₅ ) ₄ Sn ₂ Se ₆ containing Sn ₂ Se ₆ ^4- dimer intersecting with hydrazinium cation and neutral hydrazine molecule It is.

FIG. 4 shows the X-ray diffraction pattern of a tin selenide precursor film deposited by Method 1 using spin coating.

FIG. 5 shows a thermogravimetric analysis (TGA) scan of an ammonium tin sulfide (IV) precursor, (NH ₄ ) _x SnS _y .

FIG. 6 shows the X-ray diffraction pattern of a tin sulfide (IV) precursor film deposited by Method 2 using spin coating.

FIG. 7 shows the X-ray diffraction pattern of an antimony sulfide precursor film deposited by Method 2 using spin coating.

8 is a schematic diagram of a TFT device structure using spin coated metal chalcogenide semiconductor as channel material.

FIG. 9 shows a plot of I _D and I _D ^1/2 against V _G at a constant V _D = 100 V for a TFT with spin coated SnS ₂ channels fabricated using Method 1. FIG.

FIG. 10 shows a plot of drain current I _D versus source-drain voltage V _D as a function of gate voltage V _G for a TFT with spin coated SnS ₂ channel fabricated by Method 1. FIG.

FIG. 11 shows a plot of I _D and I _D ^1/2 against V _G at a constant V _D = 100 V for a TFT with spin coated SnS ₂ channels fabricated using Method 2. FIG.

FIG. 12 shows a plot of drain current I _D versus source-drain voltage V _D as a function of gate voltage V _G for a TFT with spin coated SnS ₂ channel fabricated by Method 2. FIG.

FIG. 13 shows a plot of I _D and I _D ^1/2 against V _G at a constant V _D = 100 V for a TFT with spin coated SnSe _2-x S _x channel fabricated using Method 2 will be.

FIG. 14 shows a plot of drain current I _D versus source-drain voltage V _D as a function of gate voltage V _G for a TFT with spin coated SnSe _{2 ×} S _x channel fabricated by Method 2. FIG.

FIG. 15 shows the crystal structure of hydrazium precursor, (N ₂ H ₅ ) ₄ Sn ₂ S ₆ , determined using single crystal X-ray diffraction.

FIG. 16 shows device features for spin-coated SnS ₂ channels having channel length L = 95 μm and channel width W = 1500 μm fabricated using Method 3. FIG. FIG. 16 shows a plot of drain current I _D versus source-drain voltage V _D as a function of gate voltage V _G.

FIG. 17 shows device characteristics for spin-coated SnS ₂ channels with channel length L = 95 μm and channel width W = 1500 μm fabricated using Method 3. FIG. FIG. 17 shows a plot of I _D and I _D ^1/2 against V _G at a constant V _D = 85V, used to calculate current modulation I _ON / I _OFF and saturation region shift μ _sat for tin sulfide channels. It is shown.

FIG. 18 shows device characteristics for spin-coated SnS _{2- x} Se _x channels with channel length L = 95 μm and channel width W = 1000 μm fabricated using Method 3. FIG. FIG. 18 shows a plot of drain current I _D versus source-drain voltage V _D as a function of gate voltage V _G.

FIG. 19 shows device characteristics for spin-coated SnS _{2- x} Se _x channels with channel length L = 95 μm and channel width W = 1000 μm fabricated using Method 3. FIG.

20 shows the results of X-ray light emission spectroscopy (XPS). Sn valence appears to change with the metal / chalcogenide ratio. As the S / Sn ratio varies from 1.55 to 2.02, the Sn3d core level binding energy shifts from 486.3 eV to 487.2 eV, corresponding to a decrease in Sn (II) valence and an increase in Sn (IV) valence. do. Films grown by insufficient S content have metallic properties rather than semiconducting properties.

Separated Hydrazinium Formation of film from precursors

One method, method 3 of the present invention, relates to a method of depositing a thin film of metal chalcogenide using a separate hydrazinium precursor of the metal chalcogenide.

This way

Contacting a separate hydrazinium precursor of the metal chalcogenide or metal chalcogenide mixture and a solvent having a solubilizing additive therein to form a complex solution of the precursor;

Applying the complex solution onto the substrate to produce a coating of the solution on the substrate;

Removing the solvent from the coating to produce a film of the complex on the substrate; And

Thereafter, the complex film is annealed to decompose the complex to produce a metal chalcogenide film on the substrate.

It includes.

Contacting the isolated hydrazinium precursor of the metal chalcogenide and the solvent with the solubilizing additive therein creates a complex of metal chalcogenide wherein the hydrazine is substantially replaced by the solubilizing additive to form a complex.

Suitable solvents include water, lower alcohols such as methanol, ethanol, propanol, iso-propanol, n-butanol, iso-butyl alcohol, sec-butyl alcohol, cyclohexanol, ethers such as ethyl ether, dibutyl ether, esters such as Ethyl acetate, propyl acetate, butyl acetate, other solvents such as alkylene glycols of 2 to 6 carbon atoms, dialkylene glycols of 4 to 6 carbon atoms, trialkylene glycols of 6 carbon atoms, glim, Diglyme, triglyme, propylene glycol monoacetate, DMSO, DMF, DMA, HMPA and mixtures thereof.

Solubilizing additives may be aliphatic amines of 1 to 10 carbon atoms, aromatic amines of 4 to 10 carbon atoms, aminoalcohols of 2 to 6 carbon atoms or mixtures thereof.

The aliphatic amine is preferably selected from n-propylamine, iso-propylamine, n-butylamine, sec-butylamine, iso-butylamine, pentylamine, n-hexylamine, cyclohexylamine and phenethylamine, The aromatic amine is preferably pyridine, aniline or aminotoluene. The aminoalcohol is preferably selected from ethanolamine, propanolamine, diethanolamine, dipropanolamine, triethanolamine and tripropanolamine. Other amines may also be used, provided that such amines promote the solubility of the hydrazinium precursors of the metal chalcogenide in the selected solvent.

Film deposition of hydrazine-based precursors can be performed by standard solution-based techniques using a solution of separated hydrazinium-based precursors in a solvent. Suitable solution-based techniques include spin coating, stamping, printing or dip coating using the aforementioned solutions. After removing the solvent, a short, low temperature annealing treatment (typically annealing at a temperature below about 350 ° C.) is carried out to decompose the hydrazinium chalcogenide salt from the sample and to improve the crystallinity of the metal chalcogenide film formed. .

The present invention provides a lightweight, flexible, very large area display or electronic device, constructed entirely on plastic, with semiconducting materials and processing techniques that simultaneously impart high carrier mobility and low cost processing at medium / low temperatures. And many new uses for such technologies.

The present invention enables the deposition of high quality spin-coated ultrathin films having a field size transfer rate as high as orders of magnitude higher, approximately 10 cm ² / V-sec, than conventional examples of spin coated semiconductors.

Method 3 of the present invention comprises the following four steps, namely

1. separating (synthesizing) the hydrazinium precursor of the metal chalcogenide compound;

2. forming a solution of hydrazinium precursor in a suitably selected non-hydrazinium solvent mixture;

3. solution processing the thin film of chalcogenide precursor from the solution mixture described in step 2 using techniques such as spin coating, stamping or printing; And

4. Decomposing the precursor formed using the heat achieved, for example by placing the film on a hot plate or in an oven, or by using a laser based annealing treatment, into a film of the desired metal chalcogenide.

It includes.

Solution processing in step 3 is preferably achieved by spin coating.

Heating of the film in step 4 is preferably achieved by placing the substrate containing the film on a hot plate at a temperature set at 50 ° C. to 450 ° C. for a time of 0.5 to 120 minutes.

The metal chalcogenide compound described in step 1 preferably contains the main metal and chalcogen (eg, SnS ₂ , SnSe ₂ , SnS _{2- x} Se _x , In ₂ Se ₃ , GeSe ₂ , Sb ₂ S ₃ , Sb ₂ Se ₃ , Sb ₂ Te ₃ ).

The nonhydrazine solvent of step 2 preferably comprises an organic amine (eg, propylamine, butylamine, phenethylamine, ethylenediamine).

The non-drazine-based solvent mixture of step 2 preferably contains excess chalcogen (S, Se, Te) mixed with organic amines to control the formed metal chalcogenide stoichiometry and improve film formation.

The metal chalcogenide film is in the form of a thin film, and the thin film preferably has a thickness of about 5 kPa to about 2,000 kPa, more preferably about 5 kPa to about 1,000 kPa.

The metal chalcogenide film may comprise a polycrystalline metal chalcogenide having a particle size that is equal to or greater than the dimension between the contacts in the semiconductor device. However, the metal chalcogenide film may comprise a single crystal of metal chalcogenide.

The annealing treatment step is carried out for a time and at a temperature sufficient to produce a metal chalcogenide film. The temperature is preferably about 250 ° C to about 500 ° C. More preferably about 250 ° C to about 300 ° C.

Using this technique, ternary or larger size systems, such as (SnS _{2- x} Se _x ), can also be easily formed as thin films, which allows for more detailed control of the band gap of the deposited material. do. Accordingly, the present invention can be most advantageously used to form chalcogenide thin films of main group metals (eg, Ge, Sn, Pb, Sb, Bi, Ga, In, Tl).

As a first demonstration of the present invention, a film of SnS ₂ is deposited and characterized. In this case, the metal chalcogenide film can be deposited using spin coating, although it can be deposited equally using other solution-based techniques.

After film deposition, the low temperature heat treatment of the film, typically at temperatures below about 350 ° C., results in the loss of hydrazine and hydrazium chalcogenides and degradation products of these compounds, together with the formation of crystalline films of certain metal chalcogenides.

In any of the methods of the present invention, the film produced by any method may be removed from the substrate to produce a separate film of the substrate.

The substrate is preferably made from a material having one or more of the following properties: thermal stability, ie stability up to about 300 ° C. or higher, chemical inertness to metal chalcogenides, rigid or ductile. Suitable examples of substrates include captones, polycarbonates, silicon, amorphous silicon hydrides, silicon carbide (SiC), silicon dioxide (SiO ₂ ), quartz, sapphire, glass, metals, diamond-like carbon, diamond-hydrogenated carbon, gallium nitride , Gallium arsenide, germanium, silicon-germanium, indium tin oxide, boron carbide, boron nitride, silicon nitride (Si ₃ N ₄ ), alumina (Al ₂ O ₃ ), cerium (IV) (CeO ₂ ), tin oxide ( SnO ₂ ), zinc titanate (ZnTiO ₂ ), plastic materials or combinations thereof. The metal substrate is preferably a metal foil, such as aluminum foil, tin foil, stainless steel foil or gold foil, and the plastic material is preferably polycarbonate, Mylar or Kevlar.

The process described herein is useful when forming semiconductor films for applications including, for example, thin film transistors (TFT's), light emitting devices (LED's), and data storage media.

There are many examples of metal chalcogenide systems that are potentially useful as semiconducting materials. Tin sulfide (IV), SnS ₂ is a candidate material that has attracted considerable interest as a semiconducting material for solar cells, with n-type conductivity, optical band gap ˜2.1 eV and reported migration rate of 18 cm ² / V-sec [ G. Domingo et al., Fundamental Optical Absorption in SnS ₂ and SnSe ₂ ", Phys. Rev. 143, 536-541 (1966)].

Separated Hydrazinium Manufacture of precursors

The present invention also provides a first method and a second method of preparing hydrazinium precursors of metal chalcogenides as separated products.

The first method of manufacturing hydrazinium precursors

At least one metal chalcogenide, of formula R ¹ R ² N-NR ³ R ^{4 wherein} each R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl and linear, branched Or cyclic (C ₃ -C ₆ ) alkyl], and optionally a hydrazine of the metal chalcogenide in the hydrazine compound by contacting an element chalcogen selected from S, Se, Te or a combination thereof. Producing a solution of an nium based precursor; And

Separating the hydrazinium precursor of the metal chalcogenide as a substantially pure product

It includes.

Possible mechanisms that can be implemented in the system are as follows.

(1) N ₂ H ₄ + 2X → N ₂ (gas) + 2H ₂ X

(2) 4N ₂ H ₄ + 2H ₂ X + 2MX ₂ → 4N ₂ H ₅ ⁺ + MX ₆ ^4- (in solution)

Wherein M is a metal and X is S or Se.

The second method of manufacturing hydrazinium precursors

At least one metal chalcogenide and the formula NR ⁵ R ⁶ R ^{7 wherein} each R ⁵ , R ⁶ and R ⁷ is independently hydrogen, aryl, methyl, ethyl and linear, branched or cyclic (C ₃ to C ₆ ) selected from alkyl] to contact the amine compound represented by the salt of H ₂ S, H ₂ Se or H ₂ Te to generate an ammonium precursor of the metal chalcogenide;

Ammonium-based precursors of metal chalcogenides, of formula R ¹ R ² N-NR ³ R ⁴ , wherein each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl and linear Selected from branched or cyclic (C ₃ -C ₆ ) alkyl], and the metal chalcogenide in the hydrazine compound by contacting an element chalcogen selected from S, Se, Te or a combination thereof. Generating a solution of a hydrazinium precursor; And

Separating the hydrazinium precursor of the metal chalcogenide as a substantially pure product

It includes.

It is preferred that each R ⁵ , R ⁶ and R ⁷ can be independently hydrogen, aryl, methyl and ethyl. It is preferable that all of R ⁵ , R ⁶ and R ⁷ are hydrogen.

In this method, each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl or ethyl. The hydrazine compound is particularly preferably a hydrazine, i.e., a compound when R ¹ , R ² , R ² and R ⁴ are all hydrogen, methylhydrazine or 1,1-dimethylhydrazine.

The amine compound is NH ₃ , CH ₃ NH ₂ , CH ₃ CH ₂ NH ₂ , CH ₃ CH ₂ CH ₂ NH ₂ , (CH ₃ ) ₂ CHNH ₂ , CH ₃ CH ₂ CH ₂ CH ₂ CH ₂ NH ₂ , phenethyl Amine, 2-fluorophenethylamine, 2-chlorophenethylamine, 2-bromophenethylamine, 3-fluorophenethylamine, 3-chlorophenethylamine, 3-bromophenethylamine, 4-fluoro Phenethylamine, 4-chlorophenethylamine, 4-bromophenethylamine, 2,3,4,5,6-pentafluorophenethylamine or a combination thereof is preferred.

Ammonium-based metal chalcogenide precursors can be prepared by a variety of techniques depending on the metal chalcogenide under consideration. Examples of such techniques include the simple dissolution of metal chalcogenides in an aqueous ammonium chalcogenide solution, followed by the conventional evaporation of the solution at room temperature, the solvothermal technique, and the technique by the solid state route at high temperatures. . In contrast to most metal chalcogenides that are substantially insoluble in common solvents, ammonium salts may be highly soluble in hydrazine with the violent generation of ammonia and the formation of hydrazinium salts of metal chalcogenides [LF Audrieth et al. , "The Chemistry of Hydrazine", John Wiley & Sons, New York, 200 (1951). For example, the solubility of ammonium-based SnS ₂ precursors exceeds 200 g per liter of hydrazine.

Separating the hydrazinium precursor of the metal chalcogenide as a substantially pure product from the first and second methods of the present invention may be accomplished by any suitable method or procedure known to those skilled in the art. have. Such suitable methods include the following methods, namely

1. A method of evaporating a solvent to produce hydrazinium precursors of metal chalcogenides as substantially pure solids;

2. a method in which the hydrazinium precursor of the metal chalcogenide is less soluble or substantially insoluble with the addition of a solvent to precipitate the hydrazinium precursor of the metal chalcogenide and then the precipitate is filtered; And

3. A method in which the reaction mixture is cooled to precipitate a hydrazinium precursor of a metal chalcogenide from the reaction mixture, and then the precipitate is filtered.

This includes, but is not limited to.

Since the hydrazine sites that dissolve the metal chalcogenide structure only weakly interact with the metal chalcogenide backbone, such sites can be easily removed from the precursor at low temperatures. In addition, since the starting materials are all chalcogenides (not halides or oxides), impurities of these elements are not present in the final film.

The present invention is apparent from the initial disclosed use of hydrazine hydrates as solvents for the precipitation of certain metal sulfides and selenides (zinc sulfide, copper selenide, silver-doped zinc sulfide, copper-doped zinc cadmium sulfide). Are distinguished (see US Pat. No. 6,379,585, assigned to Vecht et al., Entitled "Preparation of Sulfides and Selenides"). In the case of this prior study, solvents (always comprising water as well as hydrazine) generally allow for precipitation of transition metal chalcogenides rather than dissolution of metal chalcogenides for further solution-based processing.

The technique of the present invention is not limited to the use of hydrazines, but also hydrazine-like solvents such as 1,1-dimethyl-hydrazine and methylhydrazine, or hydrazine-like solvents and water, methanol, ethanol, acetonitrile and N, N- Mixtures with other solvents can also be used, including dimethylformamide.

The chalcogenide may further comprise elemental chalcogens such as S, Se, Te or combinations thereof.

Hydrazinium based precursors, ie hydrazium metal chalcogenides, are represented by the formula:

M _z X _q (R ¹ R ² N-NHR ³ R ⁴ ) _{2q- nz} (R ¹ R ² N-NR ³ R ⁴ ) _m

In the above formula,

M is a main group metal having valency n, n is an integer from 1 to 6;

X is a chalcogen;

z is an integer from 1 to 10;

q is an integer from 1 to 30;

m is 1 to 30.5;

Each R ¹ , R ² , R ³ and R ⁴ is independently selected from hydrogen, aryl, methyl, ethyl and linear, branched or cyclic (C ₃ -C ₆ ) alkyl.

Metal chalcogenides include metals such as Ge, Sn, Pb, Sb, Bi, Ga, In, Tl or combinations thereof and chalcogens such as S, Se, Te or combinations thereof.

In one embodiment, the metal chalcogenide can be represented by the formula MX or MX ₂ , wherein M is a metal, such as Ge, Sn, Pb, or a combination thereof, and X is a chalcogen such as S, Se , Te or a combination thereof.

In another embodiment, the metal chalcogenide can be represented by the formula M ₂ X ₃ , where M is a metal, such as Sb, Bi, Ga, In, or a combination thereof, and X is a chalcogen, S , Se, Te or a combination thereof.

In another embodiment, the metal chalcogenide can be represented by the formula M ₂ X, wherein M is Tl and X is a chalcogen such as S, Se, Te or a combination thereof.

It is preferable that the metal is Sn or Sb, and the chalcogen is S or Se.

Examples of such chalcogenide systems include the formula Sn (S _2-x Se _x ), wherein Sn is 0 to 2, including SnS ₂ and SnSe ₂ .

pellicle Electric field Effect transistor device

The present invention also provides an improved thin film field effect transistor (TFT) device having a semiconducting channel layer deposited using the four step approach described above.

Such devices made in accordance with the present invention produce the highest rates of migration currently reported for n-type solution processed devices. Device features are also described in B.A. Ridley et al., “All-Inorganic Field Effect Transistors Fabricated by Printing”, Science 286, 746-749 (1999), perform better than CdSe semiconducting membranes in which the organically induced CdSe nano Printed using soluble metal chalcogenide precursors formed using crystals.

Accordingly, the present invention includes an improved field effect transistor based on a chalcogenide channel layer that has been solution processed using the method of using the isolated hydrazinium precursors according to the present invention. This field effect transistor is a thin film field effect transistor (FET) device that holds a film of a metal chalcogenide semiconducting material as an active semiconductor layer.

The present invention relates to a source region and a drain region, a channel layer extending between the source region and the drain region and comprising a semiconductive material, a gate region disposed to be spaced apart adjacent to the channel layer, the gate region and the source region, the drain. A method of manufacturing a field effect transistor of a type having an electrically insulating layer between a region and a channel layer, the method comprising

Contacting the isolated hydrazinium precursor of the metal chalcogenide and a solvent having a solubilizing additive therein to form a complex solution of the precursor, applying the complex solution onto the substrate to coat the solution on the substrate. Forming, removing the solvent from the coating to produce a film of the complex on the substrate, and then annealing the complex film to decompose the complex to produce a metal chalcogenide film on the substrate. Preparing a channel layer comprising a film of a metal chalcogenide semiconducting material.

In one embodiment, as shown, for example, in FIG. 4 of US Pat. No. 6,180,956, the content of which is incorporated herein by reference, the source region, the channel layer, and the drain region are disposed on the surface of the substrate, and the electrically insulating layer Is disposed over the channel layer and extends from the source region to the drain region and the gate region over the electrically insulating layer.

In another embodiment, for example, as shown in FIG. 3 of US Pat. No. 6,180,956, cited above, the gate region is disposed as a gate layer on the surface of the substrate, the electrically insulating layer is disposed over the gate layer, and the source The region, channel layer and drain region are disposed over the electrically insulating layer.

The metal chalcogenide semiconducting material is in the form of a thin film, where the metal chalcogenide semiconducting material is a polycrystalline material having a particle size that is equal to or greater than the dimensions between the contacts in the semiconducting device. Thus, the present invention can provide an improved field effect transistor manufactured by the above-mentioned method.

Hydrazinium Separating precursors Without work Formation of treated membrane

The present invention also provides an alternative method for depositing a thin film of metal chalcogenide, including using a hydrazine (or other hydrazine like solvent) / chalcogenide mixture as a solvent for the metal chalcogenide or mixture of metal chalcogenides. Provide (method 1). This method does not separate hydrazinium precursors. Film deposition of hydrazinium precursors is carried out using standard solvent-based techniques, including spin coating, stamping, printing or dip coating, using the solutions mentioned above. A short low temperature annealing treatment (typically annealing at temperatures below about 350 ° C.) is then performed to remove excess hydrazine and hydrazinium chalcogenide salts from the sample and to improve the crystallinity of the formed metal chalcogenide film. do.

Method 1 did not isolate the hydrazinium precursor

At least one metal chalcogenide, of formula R ¹ R ² N-NR ³ R ⁴ , wherein each R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl, or linear, Branched or cyclic (C ₃ -C ₆ ) alkyl], and hydrazinium precursors of metal chalcogenides, optionally by contacting elemental chalcogens such as S, Se, Te or combinations thereof Creating a solution of the substance;

Applying a solution of a hydrazinium precursor of a metal chalcogenide onto a substrate to produce a film of the precursor; And

Annealing the precursor film to remove excess hydrazine and hydrazium chalcogenide salts to produce a metal chalcogenide film on the substrate.

It includes.

In addition, the present invention comprises the steps of (1) synthesizing a soluble ammonium precursor; (2) using hydrazine as a solvent for the precursor; (3) depositing the film using standard solution-based techniques (mentioned above); And (4) another method (method 2) of depositing a thin film of metal chalcogenide with a low temperature annealing treatment step. The annealing treatment step may be performed at a temperature of about room temperature to about 500 ° C., but typically the annealing temperature is performed at a temperature of about 250 ° C. to about 350 ° C.

Method 2, which does not isolate the hydrazinium precursor, is similar to Method 1, except that the chalcogenide and the amine are brought into contact first to form an ammonium precursor of the metal chalcogenide, which is then used as the hydrazine compound and The exception is that it is optionally in contact with the element chalcogen. Method 2 is

One or more metal chalcogenides and the formula NR ⁵ R ⁶ R ^{7 wherein} each R ⁵ , R ⁶ and R ⁷ is independently hydrogen, aryl, methyl, ethyl, or linear, branched or cyclic (C ₃ to C ₆ ) alkyl] to contact an amine compound represented by H ₂ S, H ₂ Se or H ₂ Te with a salt to generate an ammonium precursor of the metal chalcogenide;

Ammonium-based precursors of metal chalcogenides, of formula R ¹ R ² N-NR ³ R ⁴ , wherein each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl, or Or linear, branched or cyclic (C ₃ -C ₆ ) alkyl], and the metal chalcogen in the hydrazine compound, optionally by contacting an elemental chalcogen such as S, Se, Te or a combination thereof. Producing a solution of a hydrazinium precursor of the cargo;

Applying a solution of a hydrazinium precursor of a metal chalcogenide onto a substrate to produce a film of the precursor; And

Annealing the precursor film to remove excess hydrazine and hydrazium chalcogenide salts to produce a metal chalcogenide film on the substrate.

It includes.

Description of the drawings can be performed as follows.

1 shows thermogravimetric analysis (TGA) scans of hydrazinium tin sulfide (IV) precursors synthesized from SnS ₂ , S and hydrazine and operated at 800 ° C. at 2 ° C./min in flowing nitrogen. .

FIG. 2 shows the X-ray diffraction pattern of a tin sulfide (IV) film deposited by Method 1 using spin coating and annealed at 300 ° C. for 10 minutes. The calculated c-axis parameter is 5.98 μs, the published bulk sample value for SnS ₂ , 5.90 μs [B. Palosz et al., J. Appl. Crystallogr. 22, 622 (1989).

FIG. 3 shows the X-ray crystal structure of (N ₂ H ₄ ) ₃ (N ₂ H ₅ ) ₄ Sn ₂ Se ₆ containing Sn ₂ Se ₆ ^4- dimer intersecting with hydrazinium cation and neutral hydrazine molecule It is.

FIG. 4 shows a tin selenide (IV) precursor film deposited by Method 1 using spin coating and annealed at (a) 225 ° C., (2) 250 ° C., (3) 275 ° C., and (4) 300 ° C. FIG. X-ray diffraction pattern is shown. This film exhibits substantial c-axis preferred orientation as well as increasing crystallinity with increasing annealing treatment temperature. The c-axis parameter calculated using a 300 ° C. membrane is 6.13 Hz and is consistent with the published bulk sample values for SnSe ₂ .

FIG. 5 shows a thermogravimetric analysis (TGA) scan of ammonium tin sulfide (IV) precursor, (NH ₄ ) _x SnS _y , obtained by operating up to 800 ° C. at 2 ° C./min in flowing nitrogen.

6 is deposited by Method 2 using a spin coating method (a) unannealed temperature, (b) 140 ° C, (c) 200 ° C, (d) 250 ° C, (e) 325 ° C, (f) 400 ° C X-ray diffraction pattern of an annealed tin sulfide (IV) precursor film at. This film exhibits substantial c-axis preferred orientation as well as increasing crystallinity with increasing annealing treatment temperature. The c-axis parameter calculated using a 400 ° C. membrane is 5.95 μs and the published bulk sample value for SnSe ₂ , 5.90 μs [B. Palosz et al., J. Appl. Crystallogr. 22, 622 (1989).

FIG. 7 shows the X-ray diffraction pattern of an antimony (III) sulfide precursor film deposited by Method 2 using spin coating and annealed at (a) 250 ° C. and (b) 325 ° C. FIG. Reflectance indices based on published structural reports for Sb ₂ S ₃ are shown in the figures [D. Nodland et al., North Dakota State University, Fargo, ND, USA, ICDD Grant-in-Aid (1990)].

8 is a schematic diagram of a TFT device structure using spin coated metal chalcogenide semiconductor as channel material.

FIG. 9 calculates current modulation I _ON / I _OFF and saturation region field effect transfer rate μ for TFTs with spin coated SnS ₂ channels having length L = 25 μm and width = 1500 μm fabricated using Method 1 Plots of I _D and I _D ^1/2 against V _G at a constant V _D = 100 V used to plot.

FIG. 10 shows the source-drain voltage V _D as a function of the gate voltage V _G for a TFT having a spin coated SnS ₂ channel having length L = 25 μm and width W = 1500 μm fabricated using Method 1; Plot of drain current I _D is shown. The gate dielectric is 3000 kV SiO ₂ .

FIG. 11 calculates current modulation I _ON / I _OFF and saturation region field effect transfer rate μ for TFTs with spin coated SnS ₂ channels having length L = 25 μm and width = 1500 μm fabricated using Method 2 Plots of I _D and I _D ^1/2 against V _G at a constant V _D = 100 V used to plot. The gate dielectric is 3000 kV SiO ₂ .

FIG. 12 shows the drain for source-drain voltage V _D as a function of gate voltage V _G for a TFT with spin coated SnS ₂ channel having length L = 25 μm and width = 1500 μm fabricated using Method 2. Plot of the current I _D is shown. The gate dielectric is 3000 kV SiO ₂ .

FIG. 13 shows current modulation I _ON / I _OFF and saturation region field effects for a TFT with spin coated SnSe _{2- x} S _x channels fabricated using Method 2, length L = 25 μm and width = 1500 μm. Plots of I _D and I _D ^1/2 against V _G at a constant V _D = 100 V used to calculate the transfer rate μ. The gate dielectric is 3000 kV SiO ₂ .

FIG. 14 shows the source-drain voltage V as a function of gate voltage V _G for a TFT with spin coated SnSe _{2- x} S _x channel fabricated using Method 2 and having length L = 25 μm and width = 1500 μm. It shows a plot of the drain current I _D for _D. The gate dielectric is 3000 kV SiO ₂ .

FIG. 15 shows the crystal structure of hydrazium precursor, (N ₂ H ₅ ) ₄ Sn ₂ S ₆ , determined using single crystal X-ray diffraction. Hydrogen atoms are removed for clarity. Unit cell (contoured by dashed lines): Rhombic (P 2 ₁ 2 ₁ 2 ₁ ), a = 8.5220 (5) A, b = 13.6991 (8) A, c = 14.4102 (9) A, V = 1682.301 A ³ , and Z = 4.

FIG. 16 shows device features for spin-coated SnS ₂ channels having channel length L = 95 μm and channel width W = 1500 μm fabricated using Method 3. FIG. The gate dielectric is 2500 kV SiO ₂ . FIG. 16 shows a plot of drain current I _D versus source-drain voltage V _D as a function of gate voltage V _G.

FIG. 17 shows device characteristics for spin-coated SnS ₂ channels with channel length L = 95 μm and channel width W = 1500 μm fabricated using Method 3. FIG. The gate dielectric is 2500 kV SiO ₂ . FIG. 17 shows a plot of I _D and I _D ^1/2 for V _G at a constant V _D = 85 V used to calculate current modulation I _ON / I _OFF and saturation region shift μ _sat for tin sulfide channels. It is.

FIG. 18 shows device characteristics for spin-coated SnS _{2- x} Se _x channels with channel length L = 95 μm and channel width W = 1000 μm fabricated using Method 3. FIG. The gate dielectric is 2500 kV SiO ₂ . FIG. 18 shows a plot of drain current I _D versus source-drain voltage V _D as a function of gate voltage V _G.

FIG. 19 shows device characteristics for spin-coated SnS _{2- x} Se _x channels with channel length L = 95 μm and channel width W = 1000 μm fabricated using Method 3. FIG. The gate dielectric is 2500 kV SiO ₂ . FIG. 19 shows I _D and I _D ^1/2 for V _G at a constant V _D = 85 V, used to calculate current modulation I _ON / I _OFF and saturation region shift μ _sat for the SnS _{2- x} Se _x channel. Shows a plot of.

20 shows the results of X-ray light emission spectroscopy (XPS). Sn valence appears to change with the metal / chalcogenide ratio. As the S / Sn ratio varies from 1.55 to 2.02, the Sn3d core level binding energy shifts from 486.3 eV to 487.2 eV, corresponding to a decrease in Sn (II) valence and an increase in Sn (IV) valence. Films grown by insufficient S content have metallic properties rather than semiconducting properties.

It is important to obtain the correct metal / chalcogenide ratio from the precursor solution. Insufficient amounts of chalcogenide make the membrane excessively conductive. For example, membranes grown with insufficient S content are metallic rather than semiconducting.

This can be seen in the Sn core level binding energy measured by X-ray light emission, an indicator of the valence of Sn. When examining the Sn3d spectrum of a conventional hydrazium precursor, ie, a film with hydrazine as a solvent, one can see a broad peak centered at 486.6 eV binding energy (Figure 20).

Membranes grown by the present invention that do not contain excess S have a core level binding energy of 486.3 eV, which shifts to 487.2 eV when additional S is used. This shift in binding energy tends to shift from Sn (II) valence to Sn (IV) valence due to more highly ionized species at higher binding energies. In conclusion, the addition of S reduces the amount of film SnS and increases the SnS ₂ content of the film.

In addition, for these films, the MEIS determination of S / Sn ratio shows a trend towards improved stoichiometry that correlates with XPS results. Membranes labeled "no N ₂ H ₄ " are prepared using the method of the present invention.

membrane S / Sn No N ₂ H ₂ (Sn 10) 1.55 N ₂ H ₂ (Sn 08) 1.8 No N ₂ H ₂ excess S (Sn 11) 2.02

The present invention provides an alternative method for solution deposition of chalcogenide-based electronic materials in the form of high quality thin films for use in electronic devices. The ability to deposit from solution is very attractive because it opens up the opportunity to use many low cost, low temperature, relatively high speed techniques such as spin coating, printing, stamping and dipping. Although the discussion presented below refers mainly to the application of such films in TFT's, such discussions are not representative, and thus the electronic film deposited as such can be used equally in other electronic device devices.

Example

An exemplary embodiment of the production of a film of a metal chalcogenide semiconducting material and its TFT device is provided as follows.

Method 1

Example 1 :

Solution of SnS ₂ is to form by dissolving SnS ₂ 0.274 g (1.5 mmol) in 1.0 ml of hydrazine and sulfur 0.048 g (1.5 mmol). Significant bubbling was assumed during the dissolution process, presumably due to the production of nitrogen during the reaction. The dissolution was rather slow at room temperature and it was necessary to stir for approximately 4-6 hours to obtain a clear yellow solution. The solution was filtered and the filtrate was evaporated under a stream of nitrogen gas to finally give 0.337 g of a yellow powder. Thermal analysis of the powder showed that the solid formed decomposed at a relatively low temperature, mainly 200 ° C., to form SnS ₂ , with a weight loss of 38% observed during this process (FIG. 1).

The precursor film described above could be easily deposited on the cleaned quartz substrate by dissolving 0.055 g of SnS ₂ (0.3 mmol) in 0.5 ml of hydrazine and 0.010 g (0.3 mmol) of sulfur. Each substrate was sequentially prewashed in aqua regia, toluene, methanol and finally prewashed in concentrated aqueous ammonium hydroxide solution. SnS thin film ₂ is to form, by rotating the above-mentioned solution SnS ₂ 3-4 drops were deposited on the substrate, and the substrate / solution was left to stand for 20 minutes improves the wetting, to 2 minutes 2000 rpm while the air. The yellow film thus formed was annealed at 300 ° C. for 10 minutes under an inert atmosphere. The X-ray pattern for the formed film is shown in FIG. ₂ , which shows a crystalline film of SnS ₂ .

Example 2 :

SnSe ₂ films were also deposited using the techniques described above.

0.277 g (1 mmol) of SnSe _{2 was} readily dissolved (in minutes with stirring) in 1 ml of hydrazine, which finally gave a pale yellow solution when 0.079 g (1 mmol) of Se was added. This pale yellow color suggests that the formation of polychalcogenide did not occur during the process, although the higher the amount of Se added the more dark the solution was observed. Significant bubbling was assumed during the dissolution process, presumably due to the production of nitrogen during the reaction. The solution was evaporated under flowing nitrogen gas over several hours to induce the formation of about 0.456 g of a yellow crystalline powder. The powder lost weight rapidly while standing on the balance at room temperature, suggesting that a solvent in the structure (ie hydrazine) was slowly incorporated in the sample.

In the case of crystals collected from the product, according to a fine refinement of the single crystal structure (FIG. 3), the structure and composition comprising a Sn ₂ Se ₆ ^4- dimer in which hydrazinium cations and neutral hydrazine molecules intersect (N ₂ H ₄ ) ₃ (N ₂ H ₅ ) Sn ₂ Se ₆ . It should be noted that the structure of the product supports the mechanisms shown in Schemes (1) and (2).

Thin films of SnSe ₂ is a substrate for the above-mentioned SnSe ₂ solution 3 drops (e. G., Quartz) and deposited on, the substrate / solution was left to stand for 20 minutes, it improves the wettability, rotating the substrate at 2000 rpm for 2 minutes It was formed by. The yellow film thus formed was annealed at 225 ° C., 250 ° C., 275 ° C. and 300 ° C. for 10 minutes in an inert atmosphere. The X-ray pattern for the formed film is shown in FIG. 4, which shows increasing crystallinity with increasing annealing treatment temperature. However, even at a low temperature (<300 ° C), a crystalline film could be produced. The X-ray diffraction pattern is consistent with the case of SnSe ₂ and further shows a substantial preferred orientation.

Membranes of SnSe _{2- x} S _x (x = 1) were similarly prepared using SnS ₂ , SnSe ₂ , S, Se and hydrazine, respectively, as starting materials.

Method 2

According to the second method of the present invention for the preparation of metal chalcogenide solutions, the ammonium metal chalcogenide precursors, depending on the metal chalcogenide under consideration, simply dissolve the metal chalcogenide in an aqueous solution of ammonium chalcogenide. It may then be prepared by any suitable technique, including techniques for evaporating the solution at room temperature, solvothermal techniques, and techniques by solid state pathways at elevated temperatures.

Example 3 :

In this example, the ammonium-based tin sulfide precursor was synthesized by dissolving 548.5 mg (3 mmol) of SnS _{2 in} 85 ml of 50% by weight aqueous ammonium sulfide, (NH ₄ ) ₂ S over 4 days. This solution was filtered through a 045 μm glass microfiber filter and the resulting filtrate solution was slowly evaporated over several days under a stream of nitrogen gas to give a yellow product (˜1.05 g).

The product was washed / filtered with methanol repeatedly until the filtrate solution formed was colorless and the thermal analysis scan for the optimal product produced about 30% weight-loss transfer rate at ˜150 ° C. (which produces SnS ₂ ) ( 5). This represents a suitable composition, (NH ₄ ) ₂ SnS ₃ . The product was nominally amorphous. In other words, the product had no X-ray pattern observed in the powder diffractometer. The weight loss corresponding to the loss of ammonia and hydrogen sulfide has been initiated at temperatures as low as ambient temperature, indicating that the material can be readily decomposed into SnS ₂ . Since the SnS ₂ precursor does not need to have a fixed stoichiometric ratio, the precursor is referred to herein as (NH ₄ ) _x SnS _y .

The precursor, (NH ₄ ) _x SnS _y, was found to be highly soluble in hydrazine. For example, (NH ₄ ) _x SnS _y 80 mg could be readily dissolved in 0.5 ml of anhydrous hydrazine with vigorous production of ammonia. Thus, the membranes each used about 3 to 4 drops of precursor solution on a 0.75 inch quartz disk substrate and were rotated at 2000 rpm for 2 minutes, for example, in an inert atmospheric drybox or in air from the hydrazine solution mentioned above in air. It could be easily spin coated on the phase.

Each substrate was sequentially prewashed in aqua regia, toluene and methanol, and finally prewashed in concentrated aqueous ammonium hydroxide solution. The film formed was pale yellow in color (transparent) and was very smooth in appearance.

Five annealing treatment temperatures considered 140 ° C, 200 ° C, 250 ° C, 325 ° C and 400 ° C. For each temperature, the coated substrate was annealed for 20 minutes on the temperature controlled hotplate under an inert (nitrogen) atmosphere. X-ray studies of the film show that even though some crystallinities are not visible at temperatures as low as 200 ° C., the crystallinity gradually increased with annealing temperature (FIG. 6).

Example 4 :

As a second example of the ammonium precursor technique, a Sb ₂ S ₃ membrane was prepared.

Ammonium-based antimony sulfide precursor was synthesized by dissolving 0.250 g (0.74 mmol) of Sb ₂ S _{3 in} 10 ml of 50% by weight aqueous ammonium sulfide, (NH ₄ ) ₂ S over several hours. This solution was filtered through a 0.45 μm glass microfiber filter and the resulting filtrate solution was slowly evaporated over a period of 3 hours under a flow of nitrogen gas to give a dark color product (˜0.385 g). The precursor, (NH ₄ ) _x SbS _y, was found to be highly soluble in hydrazine. For example, (NH ₄ ) _x SnS _y 80 mg could be readily dissolved in 0.5 ml of anhydrous hydrazine with vigorous production of ammonia. Therefore, the membrane is prepared from quartz disks from the above-mentioned hydrazine solutions in an inert atmospheric drybox or in air by using 3-4 drops of precursor solution on each 0.75 inch quartz disk substrate, for example by rotating at 2000 rpm for 2 minutes. The phase could be easily spin coated.

Each substrate was sequentially prewashed in aqua regia, toluene and methanol, and finally prewashed in concentrated aqueous ammonium hydroxide solution. The film formed was pale yellow (transparent) and was smooth in appearance.

Two annealing treatment temperatures considered 250 ° C and 325 ° C. For each temperature, the coated substrate was annealed to the above defined temperature for 20 minutes on a temperature controlled hotplate in an inert (nitrogen) atmosphere. As soon as the substrate was placed on the hot plate, the color of the film immediately darkened, indicating the formation of Sb ₂ S ₃ . X-ray studies of the film show that the crystallinity gradually improved as the annealing treatment temperature increased (FIG. 7).

Example 5:

TFT device :

TFTs were prepared using the semiconducting metal chalcogenides described above as semiconducting channels. For testing purposes, the devices tested were excessively n-doped silicon substrates (also functioning as gates), 3000 Å thermally grown SiO ₂ insulation barrier layers, spin coated tin sulfide or sullenide (IV), and patterned 800 kV gold source and drain electrodes were included (FIG. 8).

For SnS ₂ semiconducting channels, the spin coating solution is dissolved in Method 1, 1.6 ml of hydrazine and 20 mg (0.11 mmol) of SnS _{2 in} 3.5 mg (0.11 mmol), or in Method 2, 1.6 ml of hydrazine. It was prepared by any of the methods of dissolving an ammonium precursor, (NH ₄ ) _x SnS _y 25 mg. In each case, 3-4 drops of tin (IV) sulfide solution were placed on a cleaned 2 cm x 2 cm silicon substrate (by a final cleaning step including placing the substrate in ammonium hydroxide for at least 1/2 hour). , Was spun in air at 3500 rpm for 1 minute. The annealing treatment sequence for the membrane of Method 1 included annealing treatment at 120 ° C. in a gradient ramp, at 120 ° C. for 20 minutes, and finally at 300 ° C. for about 5 minutes. This film performed a second annealing treatment at 300 ° C. after decomposition of the gold source and drain contacts to substantially improve device characteristics.

The annealing treatment sequence for the membrane of Method 2 included annealing treatment at 120 ° C. in a gradient lamp, at 120 ° C. for 20 minutes, and finally at 300 ° C. for about 15 minutes. The drain and gate deflection voltage characteristics of the SnS ₂ channel produced using the methods 1 and 2 are shown in FIGS. 9 to 12.

For devices fabricated using Method 1, the device characteristics were μ _sat = 0.20 cm ² / V-sec, μ _lin = 0.10 cm ² / V-sec, and I _ON / I _OFF = 7 × 10 ³ , whereas For the device manufactured using 2, the device characteristics were μ _sat = 0.07 cm ² / V-sec, μ _lin = 0.05 cm ² / V-sec, and I _ON / I _OFF = 6 × 10 ³ .

Example 6 :

A film degree of hybridized SnSe _{2- x} S _x was prepared using Method 2.

Ammonium precursors were synthesized by dissolving 0.360 g (1.3 mmol) of SnSe _{2 in} 56 ml of 50% by weight aqueous ammonium sulfide, (NH ₄ ) S ₂ over several days. This solution was filtered through a 0.45 μl glass microfiber filter and the resulting filtrate solution was slowly evaporated under a stream of nitrogen gas over several days. The dark colored product was washed thoroughly with methanol to yield 0.477 g of the dark colored product. A layer of selenide / tin sulfide (IV) precursor was prepared by dissolving 30 mg of precursor in 1.6 ml of hydrazine and rotating 3-4 drops placed on the substrate at 3500 rpm for 1 minute.

The oxide coated silicon substrate was thoroughly cleaned and immersed in the ammonium hydroxide solution for at least 1 hour or more before spin coating of the metal chalcogenide solution. The annealing treatment sequence for this membrane included annealing treatment at 120 ° C. in a gradient lamp, at 120 ° C. for 20 minutes, and finally at 300 ° C. for about 15 minutes.

The device characteristics are shown in FIGS. 13 and 14, where for n-type spin coated semiconductors, some of the highest reported values for the transfer rate are μ _sat = 1.3 cm ² / V-sec, μ _lin = 1.0 cm ² / V -sec and I _ON / I _OFF = 10 ³ .

Method 3

In the following examples, hydrazium precursors were separated from the reaction mixture. Unlike Examples 1-6, where the reaction mixture containing hydrazine is used "by itself" to cast the membrane, Examples 7-9 were cast using separate precursors.

Example 7:

SnS ₂ Membrane and device :

1.Pale yellow (N ₂ H ₅ ) ₄ Sn ₂ S ₆ crystals and powder were mixed with 0.183 g (1 mmol) of SnS _{2 in} 2 ml of hydrazine and 0.064 g (2 mmol) of S (with stirring over several hours in a nitrogen atmosphere). It was formed by dissolving to give the final yellow solution.

It should be noted that hydrazine is highly toxic and must be handled with suitable protective equipment to prevent contact with vapors or liquids. The process of evaporating to dry the solution over several hours as well as under vacuum under flowing nitrogen gas results in the formation of about 0.274 g (0.49 mmol) of hydrazinium precursor [(N ₂ H ₅ ) ₄ Sn ₂ S ₆ ]. Induced. According to the chemical analysis of the product, expected values, ie experimental values: N (19.8%), H (3.5%); Calculated Values: N (19.9%) and H (3.6%). The crystal structure shown in FIG. 15 confirms the chemical formula and shows that the precursors structurally have an edge divalent SnS ₄ tetradentate (Sn ₂ S ₆ ^4- ) anion dimer that intersects with the hydrazium cation. gave.

2. A solution of hydrazinium precursor, (N ₂ H ₅ ) ₄ Sn ₂ S ₆ , contains about 14 mg of (N ₂ H ₅ ) ₄ Sn ₂ S ₆ and S 3 mg in 3.3 ml of butylamine under nitrogen atmosphere. It was formed by stirring for hours. This formed solution was apparently transparent yellow and was suitable for solution processing. It should be noted that the solution also demonstrated using phenethylamine and ethylenediamine as solvent.

3. Solution processing of the thin film was achieved by spin coating. An excess of 2 cm × 2 cm square silicon substrate was n-doped to produce a substrate resistance <0.005 ohm-cm and coated with about 2500 μs of thermally grown SiO ₂ (measured capacitance = 1.30 × 10 ⁻⁸ μF / cm ² ). Substrates were cleaned using a standard process of soap scrub with cotton swabs, sonication in ethanol and dichloromethane, and a piranha process (1: 4 volume ratio of hydrogen peroxide: sulfuric acid). About 12 drops of the butylamine-based solution (step 2) described above was dropped through a 0.2 mm filter onto a cleaned silicon substrate. The solution was left on the substrate for about 10 seconds before initiating the rotation cycle. This rotational cycle included a process of 4000 rpm in the ramp, 45 seconds at 4000 rpm, and 0 rpm in the ramp to produce a film of metal chalcogenide precursors. The film was further dried in air by placing the substrate (with the film on top) on a preheated hotplate at 120 ° C. for 5 minutes and then transferred into a nitrogen filled drybox for the final decomposition step.

4. The decomposition step was achieved by placing the substrate (with the precursor film on top) for 20 minutes on a preheated hot plate at 270 ° C. Heating was carried out in a nitrogen atmosphere with oxygen and water content kept below 1 ppm. After heat treatment, the film was recovered from the hot plate and cooled to ambient temperature to produce a semiconducting film of tin (IV) sulfide. When measured using Medium Energy Ion Scattering Spectroscopy (MEIS), the stoichiometry of the membrane was SnS _{2.0 (1), which} was in full agreement with the expected SnS ₂ composition. Films deposited from solutions without excess S added (i.e., solutions containing only hydrazinium precursors and butylamines) generally produced films lacking sulfur, i.e., SnS _2-x , where x is about 0.5. It should be noted that This resulted in too high conductivity, which resulted in the formation of a film unsuitable for use in the TFT channel layer (ie, the film became inoperable).

TFT device :

Thin film transistors were demonstrated by depositing gold source and drain electrodes on top of the semiconducting film described in step 4. The form of the device is shown in FIG. 8. A representative plot of drain current I _D versus drain voltage V _D is shown in FIG. 16 as a function of applied gate voltage V _D for a TFT having a tin sulfide channel formed using steps 1 to 4 described above. The device operated as an n-type channel transistor operating in accumulation mode upon application of a positive gate bias. The application of a negative gate bias depletes the channel of the electronics and renders the device inoperable. At low V _D , the TFTs exhibited typical transistor behavior as I _D increased linearly with V _D. Current saturation by small resistive components was observed at high V _D as the scale layer was pinched off near the drain electrode. Current modulation (I _ON / I _OFF ) and saturation region field effect shift (μ _sat ) were calculated from plots of I _D and I _D ^1/2 versus V _G (FIG. 17), with a -60 V to 85 V gate deflection voltage ( gate sweep) and V _D = 85 V, I _ON / I _OFF = 10 ⁴ and μ _sat = 0.4 cm ² / Vs, respectively. It should be noted that the use of thinner or higher dielectric constant gate insulators (compared to currently used 2500 kV SiO ₂ layers) is expected to enable a significant reduction in device operating voltage. The line region migration rate, μ _lin = 0.38 cm ² / Vs, derived from the plot in FIG. 16 was very similar to the saturation region values. It should be noted that this was in contrast to organic and hybrid thin film devices in which the line region migration rate values were substantially smaller than the saturation region values. Since inconsistencies between these values often tend to result from trap states, the absence of such inconsistencies in the membranes of the present invention could easily demonstrate high quality membranes.

Example 8:

SnS _{2- X} Se _X Membrane and device :

1.Pale brown (N ₂ H ₅ ) ₄ Sn ₂ S _{6- X} Se _X crystals and powders were obtained from 0.183 g (1.6 mmol) of SnS ₂ and 0.147 g of SnSe _{2 in} 2 ml of freshly distilled hydrazine and 0.0128 g (4 mmol) of S. (0.53 mmol) was formed by dissolving (with stirring over several hours in a nitrogen atmosphere) to produce the final tan solution.

It should be noted that hydrazine is highly toxic and must be handled with suitable protective equipment to prevent contact with vapors or liquids.

The process of evaporating to dry the solution over several hours as well as under vacuum under flowing nitrogen gas results in the formation of about 0.628 g (0.49 mmol) of product (N ₂ H ₅ ) ₄ Sn ₂ S ₅ Se with the expected proper composition. Induced.

2. A solution of the hydrazinium precursor, (N ₂ H ₅ ) ₄ Sn ₂ S ₅ Se, of suitable composition is formed by stirring 14 mg of precursor and 3 mg of S 3 mg in 3.3 ml of butylamine under nitrogen atmosphere for about 12 hours. I was. This formed solution was apparently transparent brown and suitable for solution processing. It should be noted that the solution also demonstrated using phenethylamine and ethylenediamine as solvent.

3. Solution processing of the thin film was achieved by spin coating. The 2 cm × 2 cm square silicon substrate was excessively n-doped to produce a substrate resistance <0.005 ohm-cm and coated with about 2500 μs of thermally grown SiO ₂ . The substrate was cleaned using a standard process of soap washing with a cotton swab, sonication in ethanol and dichloromethane, and a piranha process (1: 4 volume ratio of hydrogen peroxide: sulfuric acid). About 12 drops of the butylamine-based solution (step 2) described above was dropped through a 0.2 mm filter onto a cleaned silicon substrate. The solution was left on the substrate for about 10 seconds before initiating the rotation cycle. This rotational cycle included a process of 4000 rpm in the ramp, 45 seconds at 4000 rpm, and 0 rpm in the ramp to produce a film of metal chalcogenide precursors. The film was further dried in air by placing the substrate (with the film on top) on a preheated hotplate at 120 ° C. for 5 minutes and then transferred into a nitrogen filled drybox for the final decomposition step.

4. The decomposition step was achieved by placing the substrate (with the precursor film on top) for 20 minutes on a preheated hotplate at 250 ° C. Heating was carried out in a nitrogen atmosphere with oxygen and water content kept below 1 ppm. After heat treatment, the film was recovered from the hotplate and cooled to ambient temperature to produce a semiconducting film of SnS _{2 -X} Se _X having an expected composition of about SnS _1.5 Se _0.5 .

TFT device :

Thin film transistors were demonstrated by depositing gold source and drain electrodes on top of the semiconducting film prepared as described in step 4. Drain voltage exemplary plot of drain current I _D V _D is about 18 as a function of the applied gate voltage V _D for a TFT having a SnS _{2- X X} Se channel is formed by using the above-described Step 1 to Step 4 Shown in The device operated as an n-type channel transistor operating in accumulation mode upon application of a positive gate bias. The application of a negative gate bias depletes the channel of the electronics and renders the device inoperable. At low V _D , the TFTs exhibited typical transistor behavior as I _D increased linearly with V _D. Current saturation by small resistive components was observed at high V _D as the scale layer was pinched off near the drain electrode. Current modulation (I _ON / I _OFF ) and saturation region field effect shift (μ _sat ) were calculated from plots of I _D and I _D ^1/2 against V _G (FIG. 19), with -60 V to 85 V gate deflection voltage and For V _D = 85 V, I _ON / I _OFF = 10 ⁴ and μ _sat = 1.1 cm ² / Vs, respectively. It should be noted that the use of thinner or higher dielectric constant gate insulators (compared to the currently used 2500 kV SiO ₂ layer) is expected to enable a significant reduction in device operating voltage. The line region migration rate, μ _lin = 1.1 cm ² / Vs, derived from the plot in FIG. 18 was very similar to the saturation region values.

Example 9:

The following hydrazinium precursors of the main group metal chalcogenides can also be isolated. These precursors could be used as in the above examples to produce thin films suitable for device use: SnSe ₂ , GeSe ₂ , In ₂ Se ₃ , Sb ₂ S ₃ and Sb ₂ Se ₃ .

The solution-processing techniques described were potentially useful because of the ultra-thin and relatively uniform nature (ie, unit cell thickness of less than ˜50 mm 3 or less) of the spin coated films formed. Therefore, this opens up the possibility of fabricating multilayer structures using spin-coating processes. For example, the layer of SnS ₂ may alternate with the layer of SnSe ₂ .

It may be desirable to form type 1 and type 2 quantum well structures by replacing large band gap semiconductors (or insulators) with narrow band gap semiconductors to form quantum well structures or semiconductors with different band offsets. By varying the solute concentration or rotation rate in the solution, the relative thickness of the layers of the structure can be controlled. The formed multilayer structure may be useful for device applications of solar cells, thermoelectric devices or transistor devices.

A potential advantage of the present invention is that the present invention can be implemented at much lower cost than the typical MBE or vacuum evaporation approaches currently used to form multilayer structures.

The present invention has been described above with reference to certain preferred embodiments. Those skilled in the art will understand that modifications and variations of the present invention can be made without departing from the spirit and scope of the present invention. In addition, the invention includes all such alternatives, modifications and variations that fall within the scope of the appended claims.

The present invention provides a method of depositing a film of metal chalcogenide and a method of manufacturing a field effect transistor comprising a film of metal chalcogenide. Low-cost metal chalcogenide semiconducting materials prepared according to the method include flat panel displays, nonlinear optical / photoconductive devices, chemical sensors, light emitting and light transfer layers in light emitting diodes, thin film transistors, channel layers in field effect transistors, And optical data storage media including optical data storage phase change media.

Claims (22)

A method of depositing a film of metal chalcogenide, Contacting the separated hydrazinium precursor of the metal chalcogenide and a solvent having a solubilizing additive therein to form a complex solution of the precursor; Applying the complex solution onto a substrate to produce a coating of the solution on the substrate; Removing the solvent from the coating to form a film of the complex on the substrate; And Thereafter annealing the complex film to produce a metal chalcogenide film on the substrate. How to include. The solvent of claim 1 wherein the solvent is water, lower alcohol, ether, ester, alkylene glycol of 2 to 6 carbon atoms, dialkylene glycol of 4 to 6 carbon atoms, trialkyl of 6 carbon atoms Lene glycol, glim, diglyme, triglyme, propylene glycol monoacetate, DMSO, DMF, DMA, HMPA and mixtures thereof. The method of claim 2 wherein the solubilizing additive is selected from the group consisting of aliphatic amines of 1 to 10 carbon atoms, aromatic amines of 4 to 10 carbon atoms, aminoalcohols of 2 to 6 carbon atoms, or mixtures thereof. Which method is chosen. The method of claim 2, wherein the solubilizing additive is n-propylamine, iso-propylamine, n-butylamine, sec-butylamine, iso-butylamine, pentylamine, n-hexylamine, cyclohexylamine, phenethylamine , Pyridine, aniline, aminotoluene, ethanolamine, propanolamine, diethanolamine, dipropanolamine, triethanolamine, tripropanolamine and mixtures thereof. The method of claim 1, wherein the separated hydrazinium precursor of the metal chalcogenide At least one metal chalcogenide, of formula R ¹ R ² N-NR ³ R ^{4 wherein} each R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl and linear, branched Or an element chalcogen selected from the group consisting of cyclic (C ₃ -C ₆ ) alkyl], and optionally S, Se, Te and combinations thereof. Producing a solution of the hydrazinium precursor of the metal chalcogenide; And Separating the hydrazinium precursor of the metal chalcogenide as a substantially pure product It is prepared by a process comprising a. The method of claim 1, wherein the separated hydrazinium precursor of the metal chalcogenide At least one metal chalcogenide and the formula NR ⁵ R ⁶ R ^{7 wherein} each R ⁵ , R ⁶ and R ⁷ is independently hydrogen, aryl, methyl, ethyl and linear, branched or cyclic (C ₃ to C ₆ ) alkyl selected from the group consisting of; and a salt of H ₂ S, H ₂ Se or H ₂ Te by contacting to generate an ammonium precursor of the metal chalcogenide; The ammonium precursor of the metal chalcogenide, formula R ¹ R ² N-NR ³ R ⁴ , wherein each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl And an element chalcogen selected from the group consisting of linear, branched or cyclic (C ₃ -C ₆ ) alkyl], and optionally S, Se, Te and combinations thereof. Producing a solution of the hydrazinium precursor of the metal chalcogenide in the hydrazine compound; And Separating the hydrazinium precursor of the metal chalcogenide as a substantially pure product It is prepared by a process comprising a. A source layer and a drain region, a channel layer extending between the source region and the drain region and comprising a semiconducting material, a gate region disposed to be spaced apart adjacent to the channel layer, the gate region and the source region, the drain region and the channel A method of manufacturing a field effect transistor of the type having an electrically insulating layer between layers, Contacting the separated hydrazinium precursor of the metal chalcogenide and a solvent having a solubilizing additive therein to form a complex solution of the precursor; Applying the complex solution onto a substrate to form a coating of the solution on the substrate; Removing the solvent from the coating to form a film of the complex on the substrate; And subsequently annealing the complex film to produce a metal chalcogenide film on the substrate to produce a channel layer comprising a film of a metal chalcogenide semiconducting material prepared by a process. How to include. 8. The method of claim 7, wherein the metal chalcogenide film is in the form of a thin film having a thickness of about 5 kPa to about 2,000 kPa. 8. The method of claim 7, wherein said metal chalcogenide film comprises polycrystalline metal chalcogenide or a single crystal of said metal chalcogenide. 10. The method of claim 9, wherein the metal chalcogenide film is polycrystalline with a particle size that is equal to or greater than the dimension between the contacts in the semiconductor device. 8. The metal chalcogenide of claim 7, wherein the metal chalcogenide is selected from the group consisting of Ge, Sn, Pb, Sb, Bi, Ga, In, Tl, and combinations thereof, and S, Se, Te, and combinations thereof. Chalcogen selected from the group consisting of. 8. The method of claim 7, wherein said annealing step is performed for a time sufficient to produce said metal chalcogenide film and at a temperature. 13. The method of claim 12, wherein the temperature is about 25 ° C to about 500 ° C. A field effect transistor manufactured by the method of claim 7. A method for preparing an isolated hydrazinium precursor of a metal chalcogenide, At least one metal chalcogenide, of formula R ¹ R ² N-NR ³ R ^{4 wherein} each R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl and linear, branched Or an element chalcogen selected from the group consisting of cyclic (C ₃ -C ₆ ) alkyl], and optionally S, Se, Te and combinations thereof. Producing a solution of the hydrazinium precursor of the metal chalcogenide; And Separating the hydrazinium precursor of the metal chalcogenide as a substantially pure product How to include. A method for preparing an isolated hydrazinium precursor of a metal chalcogenide, At least one metal chalcogenide and the formula NR ⁵ R ⁶ R ^{7 wherein} each R ⁵ , R ⁶ and R ⁷ is independently hydrogen, aryl, methyl, ethyl and linear, branched or cyclic (C ₃ to C ₆ ) alkyl selected from the group consisting of; and a salt of H ₂ S, H ₂ Se or H ₂ Te by contacting to generate an ammonium precursor of the metal chalcogenide; The ammonium precursor of the metal chalcogenide, formula R ¹ R ² N-NR ³ R ⁴ , wherein each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl And an element chalcogen selected from the group consisting of linear, branched or cyclic (C ₃ -C ₆ ) alkyl], and optionally S, Se, Te and combinations thereof. Producing a solution of the hydrazinium precursor of the metal chalcogenide in the hydrazine compound; And Separating the hydrazinium precursor of the metal chalcogenide as a substantially pure product How to include. Hydrazinium metal chalcogenides represented by the formula: M _z X _q (R ¹ R ² N-NHR ³ R ⁴ ) _2q-nz (R ¹ R ² N-NR ³ R ⁴ ) _m In the above formula, M is a main group metal having valency n, n is an integer from 1 to 6; X is a chalcogen; z is an integer from 1 to 10; q is an integer from 1 to 30; m is 1 to 30.5; Each R ¹ , R ² , R ³ and R ⁴ is independently selected from the group consisting of hydrogen, aryl, methyl, ethyl and linear, branched or cyclic (C ₃ -C ₆ ) alkyl. The hydrazin according to claim 17, wherein the metal is selected from the group consisting of Ge, Sn, Pb, Sb, Bi, Ga, In, and Tl, and the chalcogen is selected from the group consisting of S, Se, and Te. Metal chalcogenides. A method of depositing a film of metal chalcogenide, At least one metal chalcogenide, of formula R ¹ R ² N-NR ³ R ^{4 wherein} each R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl and linear, branched Or an element chalcogen selected from the group consisting of cyclic (C ₃ -C ₆ ) alkyl], and optionally S, Se, Te and combinations thereof. Producing a solution of a hydrazinium precursor of the cargo; Applying a solution of the hydrazinium precursor of the metal chalcogenide onto a substrate to produce a film of the precursor; And Annealing the precursor film to remove excess hydrazine and hydrazium chalcogenide salts to form a film of the metal chalcogenide on the substrate. How to include. A method of depositing a film of metal chalcogenide, At least one metal chalcogenide and the formula NR ⁵ R ⁶ R ^{7 wherein} each R ⁵ , R ⁶ and R ⁷ is independently hydrogen, aryl, methyl, ethyl and linear, branched or cyclic (C ₃ to C ₆ ) alkyl selected from the group consisting of; and a salt of H ₂ S, H ₂ Se or H ₂ Te by contacting to generate an ammonium precursor of the metal chalcogenide; The ammonium precursor of the metal chalcogenide, formula R ¹ R ² N-NR ³ R ⁴ , wherein each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen, aryl, methyl, ethyl And an element chalcogen selected from the group consisting of linear, branched or cyclic (C ₃ -C ₆ ) alkyl], and optionally S, Se, Te and combinations thereof. Producing a solution of the hydrazinium precursor of the metal chalcogenide in the hydrazine compound; Applying a solution of the hydrazinium precursor of the metal chalcogenide onto a substrate to produce a film of the precursor; And Annealing the precursor film to remove excess hydrazine and hydrazium chalcogenide salts to form a film of the metal chalcogenide on the substrate. How to include. Contacting at least one metal chalcogenide with (i) a hydrazine compound or (ii) an ammonium salt compound and then a hydrazine compound to produce a solution of the hydrazinium precursor of the metal chalcogenide; Applying a solution of the hydrazinium precursor of the metal chalcogenide onto a substrate to produce a film of the precursor; And Annealing the precursor film under conditions sufficient to produce the metal chalcogenide film A field effect transistor comprising a channel layer having a metal chalcogenide film prepared by a method comprising a. A method of manufacturing a metal chalcogenide film in a field effect transistor, Contacting at least one metal chalcogenide with (i) a hydrazine compound or (ii) an ammonium salt compound and then a hydrazine compound to produce a solution of the hydrazinium precursor of the metal chalcogenide; Applying a solution of the hydrazinium precursor of the metal chalcogenide onto a substrate to produce a film of the precursor; And Annealing the precursor film under conditions sufficient to produce the metal chalcogenide film How to include.