CN111009452B

CN111009452B - Two-dimensional semiconductor with geometric structure and forming method

Info

Publication number: CN111009452B
Application number: CN201811167013.2A
Authority: CN
Inventors: 杨东翰; 韩羽唯; 张锌权; 陈奕彤; 李奕贤
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-10-08
Filing date: 2018-10-08
Publication date: 2022-04-26
Anticipated expiration: 2038-10-08
Also published as: CN111009452A

Abstract

The invention discloses a method for forming a two-dimensional semiconductor with a geometric structure, which comprises the following steps: forming a nano-layer; arranging two-dimensional material on a substrate; forming a medium layer on the two-dimensional material; transferring the medium layer and the two-dimensional material from the substrate to the nano-layer; removing the medium layer to leave the two-dimensional material on the surface of the nano-layer. By the formation method of the two-dimensional semiconductor with the geometric structure, the nano-micro structure is utilized to promote and control the two-dimensional material on the field emission effect and the photon excitation efficiency.

Description

Two-dimensional semiconductor with geometric structure and forming method

Technical Field

The present invention relates to a two-dimensional semiconductor with a geometric structure and a forming method thereof, and more particularly, to a two-dimensional semiconductor with a geometric structure and a forming method thereof capable of improving an electron field emission effect and a photon excitation effect.

Background

When electrons are accelerated by a high electric field, the electrons are emitted from the surface of an object, which is called an electron field emission effect, and the effect can be applied to a photoelectric element. On the other hand, although the two-dimensional semiconductor has very high photoelectric conversion efficiency and can be applied to a next generation photoelectric element, the two-dimensional semiconductor has very low efficiency for an electron field emission effect, and this phenomenon is observed only at the edge of a material, and thus the field emission effect cannot be practically applied. In addition, the difficulty that cannot be overcome in the industry is that the different recessed portions of the two-dimensional material affect the uniformity of the material, and thus the characteristics of photon excitation are difficult to control.

In the prior art, there is no way to control the position of the two-dimensional semiconductor material where the field emission effect occurs, the field emission effect can only be observed at the edge or specific position of the two-dimensional semiconductor material, and the characteristics and stability are not commercially valuable.

In a patent of the patent Cooperation treaty application (WO2017/195118), a structure comprising a compound semiconductor in contact with a transition metal dichalcogenide layer, wherein the metal dichalcogenide layer is in contact with a metal substrate, the semiconductor compound comprises nanowires, the compound semiconductor comprises SiC or ZnO, and the transition metal dichalcogenide comprises MoS is disclosed₂、MoSe₂And the like. The patent is for improving the quantum efficiency of a compound semiconductor, and the manufacturing method thereof cannot improve the efficiency of the electron field emission effect.

In a chinese patent application (CN106477621A), a method for preparing a layered zinc hydroxide nanocone is disclosed, which is characterized by comprising the following steps: step 1: mixing a metal zinc salt, an alkali source and an anionic surfactant in a reaction solvent of pure water; step 2: and (3) heating the uniformly mixed solution obtained in the step (1) in a water bath for reaction. The patent discloses that layered zinc hydroxide nano sheets, nano belts and nano cones with different morphologies can be synthesized, as well as zinc oxide nano rods, nano particles and the like, and discloses that an alkali source (hexamethylenetetramine) and sodium dodecyl sulfate jointly act to obtain the layered zinc hydroxide nano cones. However, the patent is a preparation and stripping method of layered zinc hydroxide and zinc oxide nanocones, and the patent is not used for improving the efficiency of electron field emission effect.

In addition, in a chinese patent application (CN104947070A), a method for preparing a molybdenum disulfide thin film is disclosed, which is characterized by comprising the following steps: a. plating an oxide buffer layer matched with the size of a molybdenum disulfide crystal lattice on a silicon substrate; b. and growing a molybdenum disulfide film on the surface of the substrate by using a CVD method. However, said patent is directed to the direct growth of large area, high quality, low defect molybdenum sulfide (MoS) on oxide buffer coated silicon substrates₂) Thin films, are not used to improve the efficiency of the electron field emission effect.

In the U.S. patent application (US2014/0245946a1), a method of producing a transition metal dichalcogenide layer on a transfer substrate is disclosed, comprising: seeding aromatic molecules on the surface of a growth substrate; growing a layer of metal dichalcogenide on the surface of the growth substrate by chemical vapor deposition, and inoculating with aromatic molecules; and contacting the seeded aromatic molecule with a solvent that releases the transition metal dichalcogenide from the growth substrate. However, the patent discloses the synthesis and transfer of transition metal disulfide layers on different surfaces, and is not intended to improve the efficiency of electron field emission effects.

As is apparent from the above description, no effective process is proposed in the prior art for improving the efficiency of electron field emission. Moreover, most studies indicate that the observed field emission properties are mainly due to the random nature of the layered two-dimensional material and the presence of sharp protruding "edges". It is difficult to ideally uniformly control the edges of the two-dimensional material perpendicular to the substrate, which can increase the difficulty of generating large area electron emitters with acceptable reproducibility.

Therefore, there is a need to design a two-dimensional semiconductor with geometric structure and a forming method thereof, which can improve and control the result of the two-dimensional material on the field emission effect by using the nano-micro structure, and simultaneously improve the photon excitation effect and improve the defects of the prior art.

Disclosure of Invention

The invention aims to provide a method for forming a two-dimensional semiconductor with a geometric structure, which can improve the efficiency of the two-dimensional semiconductor on electron field emission effect and photon excitation effect.

In accordance with the above objects, the present invention provides a method for forming a two-dimensional semiconductor with a geometric structure, comprising the steps of:

forming a nano-layer;

arranging a two-dimensional material on a substrate;

forming a medium layer on the two-dimensional material;

transferring the medium layer and the two-dimensional material from the substrate to the nano-layer;

and removing the medium layer to leave the two-dimensional material on the surface of the nano-layer.

Another objective of the present invention is to provide a two-dimensional semiconductor with a geometric structure, through which the nano-microstructure can enhance and control the effect of the two-dimensional material on the field emission effect and the photon excitation effect.

In accordance with the above object, the present invention provides a two-dimensional semiconductor having a geometric structure, comprising:

a two-dimensional material;

and a nanolayer having a geometric structure, the two-dimensional material being disposed on the geometric structure of the nanolayer;

wherein the geometric structures of the nanolayers have a pitch of 50-100 nanometers.

Has the advantages that:

by the two-dimensional semiconductor with the geometric structure and the forming method, the two-dimensional transition metal dichalcogenide monolayer is transferred to the vertically arranged one-dimensional zinc oxide nano array to induce the geometric modulation of the semiconductor monolayer and further enhance the electron emission. A semiconductor monolayer having a sharp one-dimensional nanoarray is used to achieve effective field emission with excellent long-term emission stability in a low on-electric field.

Drawings

FIG. 1 is a flow chart illustrating the steps of a method of forming a two-dimensional semiconductor device having a geometric structure according to the present invention;

FIG. 2 is a schematic diagram illustrating the formation of a two-dimensional semiconductor device having a geometric structure according to the present invention;

FIGS. 3a and 3b are schematic views of parallel nanostructures according to the present invention;

FIG. 4a is an electron microscope image of a one-dimensional zinc oxide nano-array substrate (nanorod) of the present invention;

FIG. 4b is an electron microscope image of a one-dimensional zinc oxide nanoarray substrate (nanocone) of the present invention;

FIGS. 5 a-5 c are electron microscope images of two-dimensional transition metal dichalcogenide monolayers on nanorods of the present invention;

FIGS. 6 a-6 c are electron microscope images of a two-dimensional transition metal dichalcogenide monolayer coated on a nanocone according to the present invention;

FIG. 7 is a schematic diagram of measuring two-dimensional semiconductor measurement field emission with geometry of the present invention;

fig. 8 is a graph showing J-E characteristics of field emission of a two-dimensional semiconductor having a geometry to which the present invention is applied.

Reference numerals:

s101 to S105

20 two-dimensional semiconductor with geometrical structure

201 silicon substrate

202 two-dimensional material

203 media layer

204 nanolayer

205 nano rod

206 nanometer cone

301 nanolayer

302 nano layer

401 nanometer rod

402 nanometer cone

501 nanometer rod

601 nanometer cone

70 two-dimensional semiconductor

71 stainless steel support

80 two-dimensional semiconductor

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Fig. 1 is a flowchart illustrating a method for forming a two-dimensional semiconductor with a geometric structure according to the present invention, and fig. 2 is a schematic diagram illustrating a method for forming a two-dimensional semiconductor with a geometric structure according to the present invention. As shown in fig. 1 and 2, the method for forming the two-dimensional semiconductor 20 with a geometric structure according to the present invention includes the following steps, in step S101, a nano-layer is formed. In this step, the nanolayers are preferably of the same natureGeometric nano-layer, while in the preferred embodiment of the invention, zinc nitrite hexahydrate ((Zn (NO)₂)₂.6H₂O)) and hexamethylenetetramine (C)₆H₁₂N₄) Dissolved in a solution of deionized water, and the substrate to be synthesized into a zinc oxide nano-array is placed in this solution and heated to form the nano-layer 204, and the substrate is preferably a gallium-doped zinc oxide (GZO)/silicon (Si) substrate.

In step S102, a two-dimensional material is disposed on a substrate. In one embodiment of the present invention, two-dimensional materials are grown on a silicon substrate by, for example, Chemical Vapor Deposition (CVD). In the present invention, the two-dimensional material 202 is preferably a two-dimensional (2D) Transition Metal Dichalcogenide (TMD), and the Transition Metal Dichalcogenide is preferably molybdenum sulfide (MoS)₂) Or molybdenum diselenide (MoSe)₂) But is not limited herein. Further, on the silicon substrate 201, an atomic layer of a large-area and highly crystalline two-dimensional material 202 (including molybdenum sulfide (MoS)) was synthesized by an ambient pressure Chemical Vapor Deposition (CVD) method₂) And molybdenum diselenide (MoSe)₂))。

In step S103, a medium layer is formed on the two-dimensional material. In an embodiment of the present invention, the medium layer 203 comprises a polymer material, and a polymer layer is formed on the two-dimensional material 202 on the silicon substrate 201 by, for example, spin coating, water transfer, or thermal gel. For example, in two-dimensional transition metal dichalcogenides (molybdenum oxide (MoS)₂) Or molybdenum diselenide (MoSe)₂) Poly (methyl methacrylate), PMMA) or Polydimethylsiloxane (PDMS) was spin-coated on the sample at 1000 rpm.

In step S104, the medium layer and the two-dimensional material are transferred from the substrate onto the nanolayer. The transfer method includes etching, but is not limited in the present invention. In an embodiment of the invention, the polymer layer with the two-dimensional material 202 is transferred onto the nano-layer 204 by etching, and a contact point between the two-dimensional material 202 and the nano-layer 204 is deformed due to different stresses.

Further, a two-dimensional transition metal dichalcogenide 202 monolayer is formed from Silicon (SiO) using a polymethylmethacrylate assisted process₂the/Si) substrate 201 is transferred to a one-dimensional zinc oxide nanoarray substrate (nanorod arrays (ZnO nanoros, ZNRs)205 or nanocone arrays (ZnO nanotubes, ZNTs) 206). After baking, the polymethylmethacrylate-coated two-dimensional material 202 is completely immersed in a potassium hydroxide (KOH) solution (1M) to etch the Substrate (SiO)₂Si) (lift-off process) until there is a two-dimensional material 202 (MoS)₂Or MoSe₂) The polymethyl methacrylate (2) floats in the potassium hydroxide solution. After repeated rinsing with deionized water to remove potassium hydroxide residue, the two-dimensional material 202 coated with polymethyl methacrylate was captured.

Finally, in step S105, the medium layer is removed, so that the two-dimensional material remains on the surface of the nanolayer. In one embodiment of the present invention, the polymer layer is removed to leave the two-dimensional material 202 on the surface of the nanolayer 204, and the two-dimensional material 202 sample is left on the surface of the nanolayer 204 by dissolving the polymethyl methacrylate with acetone.

Still referring to fig. 2, the two-dimensional semiconductor 20 with geometry comprises mainly a two-dimensional material 202 and a nanolayer 204. The two-dimensional material 202 is disposed on the two-dimensional semiconductor 20 having a geometric structure, and the two-dimensional material 202 is disposed on the nano-layer 204, and a contact point of the two-dimensional material 202 and the nano-layer 204 is deformed due to different stresses. Wherein the geometric structure of the nanolayer 204 comprises an array, the geometric structure of the nanolayer 204 has a pitch of 50-100 nm, preferably 50 nm, and the density of the nanolayer 204 is 2 × 10⁹/cm². The nanolayer 204 of the present invention can be a one-dimensional nanoarray, as shown in fig. 2, the one-dimensional nanoarray can be a one-dimensional nanocone array or a one-dimensional nanorod array, which is not limited to . The one-dimensional nanoarray can be a one-dimensional zinc oxide nanoarray, or the nanolayer 204 can be made of silicon, noble metal, silicon oxide, aluminum oxide, hafnium oxide or titanium oxide, when the nanolayer 204 is made of noble metal, the noble metal can be gold, silver, platinum or palladium, and the height of the conical projection of the one-dimensional nanocone is equal to347 + -25 nm. After the two-dimensional material 202 is laid, the distance between the highest position and the lowest position of the two-dimensional material 202 is 80 +/-30 nm.

The two-dimensional material 202 may be composed of two-dimensional transition metal dichalcogenide, graphene, or boron nitride. The geometry of the nanolayer 204 can be pyramidal, conical, triangular pyramidal, quadrangular pyramidal, pentagonal pyramidal, hexagonal pyramidal, polygonal pyramidal, or bullet shaped. When the nanolayer 204 is pyramidal, its pointed cone angle is less than 2 °. Additionally, in various embodiments, the nanolayers 301 may be nanostructures that are parallel to each other, as shown in fig. 3 a. When the nanolayer 302 is conical, its top is a cylinder with curvature, and the curvature of the semicircle is preferably less than 10 nm, and the cross-sectional area of the surface of the nanolayer 302 is preferably less than 100 nm, as shown in fig. 3 b. In an embodiment of the present invention, a material layer may be further plated on the nano-layer 302, and the material layer is preferably a noble metal material, and the noble metal may be gold, silver, platinum or palladium. The nanolayer 204 is coated with a material layer that induces a surface plasma resonance (plasmon resonance) property, and the free electrons in the metal of the material layer have an opportunity to interact with the electrons in the two-dimensional material 202, thereby increasing the electro-optic properties of the two-dimensional material 202.

Further, in the process of synthesizing a two-dimensional semiconductor having a geometric material, the synthesis of a two-dimensional transition metal dichalcogenide, a one-dimensional zinc oxide nanostructure and a hybrid thereof (2D-1D heterostructure) can be performed at 2 × 2cm²Is highly uniformly spread within the semiconductor area. The geometry of two-dimensional transition metal dichalcogenides is modulated using provided nanostructures, including zinc oxide (ZnO) nanorods (ZNR) and zinc oxide (ZnO) nanocones (ZNT).

Zinc oxide nanorods (ZNRs) were synthesized on sputtered gallium-doped zinc oxide (GZO, Ga 0.01, and Zn 0.99) seed layers by hydrothermal reaction. The gallium-doped zinc oxide thin film shows good conductivity and provides a suitable surface for nanorod growth with good vertical orientation. The blunt nanorods 401 are shown in a Scanning Electron Microscope (SEM) image to be crystallized along the c-axis and have six prismatic facets, as shown in fig. 4 a.

In addition, the apex curvature of the nanorods, such as blunt and conical tips, can be precisely fabricated by controlling the etching process. In fig. 4b, the electron microscope image of the nanocone 402 shows a perfectly aligned conical tip after the etching process, and the length of the nanocone 302(347 ± 25nm) is only slightly shorter than the length of the nanorod 401.

Two-dimensional transition metal dichalcogenide (MoS)₂) The monolayer can be uniformly supported on the rods of nanorods 501 (fig. 5 a-5 c) and results in a corrugated morphology. In contrast, two-dimensional transition metal dichalcogenides (MoS)₂) The monolayer is tightly overlaid on the pyramidal shape of the nanocone 601 (fig. 6 a-6 c) and results in a tent-like morphology, indicating that the morphology of the two-dimensional transition metal dichalcogenide monolayer can be significantly tuned by geometrically controlling the one-dimensional array of perpendicular arrangements. For one-dimensional nanorods, the two-dimensional transition metal dichalcogenide monolayer exhibits more ripples oriented along the spatial distribution of the sharp one-dimensional array, which can be seen as the formation of sharp protrusions on the two-dimensional transition metal dichalcogenide monolayer. Similar 2D-1D heterostructures can be obtained with two-dimensional transition metal dichalcogenide monolayers and exhibit similar surface morphologies. During the removal of a single layer of polymethylmethacrylate from an acetone solution, the tensile stress will be related to the apex geometry of the supported one-dimensional array and further create ripples with spatial alignment of the two-dimensional single layer and the one-dimensional array.

FIG. 7 is a schematic diagram of measuring field emission of a two-dimensional semiconductor with geometry according to the present invention, and FIG. 8 is a J-E characteristic curve diagram of field emission of a two-dimensional semiconductor with geometry according to the present invention. In order to study the performance of two-dimensional semiconductors with geometric structures, electron field emission experiments were performed in a high vacuum system at 5X 10^-7Torr (torr) as shown in fig. 8. The two-dimensional semiconductor 70 was mounted on a stainless steel holder 71 as a cathode, and the anode was a molybdenum probe (diameter 1 mm). Current-voltage switching is performed by applying a dc voltage across the two-dimensional semiconductor and the anode. Fig. 8 shows field emission current density-field strength characteristics of various two-dimensional semiconductors having geometric structures. As expected, two-dimensional semiconductor 80 (with MoS)₂Or MoSe₂) Exceeds a detectable limit until a maximum application ≈ 20V μm^-1Of the electric field of (a).

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A method of forming a two-dimensional semiconductor having a geometric structure, comprising the steps of: forming a nano layer, wherein the nano layer has a geometric structure, and the geometric structure is conical, polygonal conical or bullet-shaped; arranging a two-dimensional material on a substrate; forming a medium layer on the two-dimensional material; transferring the medium layer and the two-dimensional material from the substrate onto the nanolayer; and removing the medium layer to leave the two-dimensional material on the surface of the nano-layer.

2. The method of forming a two-dimensional geometrically-structured semiconductor according to claim 1, wherein zinc nitrite hexahydrate ((Zn (NO) is added in the step of forming the nanolayer₂)₂．6H₂O)) and hexamethylenetetramine (C)₆H₁₂N₄) Dissolving the substrate in deionized water, and putting the substrate of the one-dimensional zinc oxide nano array into the solution to be heated so as to form the nano layer.

3. The method of claim 1, wherein the two-dimensional material is a transition metal dichalcogenide.

4. The method of claim 3, wherein in the step of disposing the two-dimensional material on the substrate by a chemical vapor deposition method, perylene-3, 4,9, 10-tetracarboxylic acid tetrapotassium salt (PTAS) with high temperature stability is used as a seeding promoter to enhance growth, and the chemical vapor deposition system is heated, and the two-dimensional material monolayer is synthesized under atmospheric pressure.

5. The method of claim 1, wherein poly (methyl methacrylate), PMMA, is spin coated on the two-dimensional material at a speed of 1000rpm in the step of forming the medium layer on the two-dimensional material.

6. The method of claim 5, wherein in the step of transferring the medium layer and the two-dimensional material from the substrate to the nano-layer, the substrate having the medium layer and the two-dimensional material thereon is further completely immersed in a potassium hydroxide (KOH) solution to etch the substrate until the medium layer having the two-dimensional material floats in the KOH solution, and the two-dimensional material coated with the medium layer is captured after repeatedly rinsing with deionized water to remove residues of the KOH solution.

7. The method of claim 5, wherein in the step of removing the medium layer to leave the two-dimensional material on the surface of the nano-layer, the polymethyl methacrylate is dissolved using acetone to remove the medium layer to leave the two-dimensional material on the surface of the nano-layer.

8. A two-dimensional semiconductor having a geometric structure, comprising: a two-dimensional material; and a nanolayer having a geometry, and the two-dimensional material is disposed on the geometry of the nanolayer; wherein the geometric structures of the nanolayers have a pitch of 50-100 nanometers and are cone-shaped, polygonal cone-shaped, or bullet-shaped, and the two-dimensional material is deformed correspondingly according to the geometric structures.

9. The geometrically structured two-dimensional semiconductor of claim 8, wherein the two-dimensional material is a two-dimensional transition metal dichalcogenide, graphene, or boron nitride.

10. The two-dimensional semiconductor of claim 8, wherein the geometric structure of the nanolayer is a one-dimensional zinc oxide nanoarray substrate.

11. The geometrically structured two-dimensional semiconductor of claim 8, wherein the geometric structures of the nanolayers are arranged in an array.

12. The two-dimensional semiconductor device of claim 11, wherein the array is arranged at a density of 2 x 10⁹ /cm²。

13. The geometrically structured two-dimensional semiconductor of claim 8, wherein the material of the nanolayer is silicon, a noble metal, silicon oxide, aluminum oxide, hafnium oxide, or titanium oxide.

14. The two-dimensional semiconductor of claim 8, wherein the geometric structures of the nanolayers are nanostructures that are parallel to each other.

15. The two-dimensional geometrically shaped semiconductor of claim 14 wherein the spacing of the nanostructures is 50 nanometers.

16. A two-dimensional geometrically shaped semiconductor as described in claim 8 wherein said nanolayer is further coated with a layer of material.

17. A two-dimensional geometrically shaped semiconductor as recited in claim 16, wherein said material layer is a noble metal material layer.

18. The geometrically-structured two-dimensional semiconductor of claim 17, wherein the layer of noble metal material comprises a layer of gold, silver, platinum, or palladium material.