JP2006240898A - Method for doping of carbon nanotube by solution treatment, semiconductor device, and method of forming the semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for doping carbon nanotube by a solution treatment, a semiconductor device and a method of forming the semiconductor device. <P>SOLUTION: This doping method for carbon nanotube includes a process for exposing the carbon nanotube to a one-electron oxidizer in a solution phase. Further, there are provided a method of forming a carbon nanotube FET device and also a semiconductor device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is an application with a priority claim based on a provisional application filed on March 2, 2004, application number 60 / 549,185, the contents of which are hereby incorporated by reference. included. The present invention relates to nanostructures, and more particularly to a solution processing method for doping carbon nanotubes (CN).

  In the field of molecular nanoelectronics, few materials are as promising as nanotubes, especially carbon nanotubes, which contain a hollow graphite cylinder. Nanotubes are microelectronic devices such as diodes and transistors, depending on the electrical properties of the nanotubes. Nanotubes are specific for their size, shape, and physical properties. Structurally, carbon nanotubes resemble a hexagonal lattice of carbon wound in a cylindrical shape.

  Besides showing interesting quantum behavior at low temperatures, carbon nanotubes exhibit at least two important properties: nanotubes can be either metals or semiconductors, depending on their chirality (ie, morphological structure). Metallic carbon nanotubes can propagate a very large current density with a certain resistivity. Semiconductor carbon nanotubes can be switched on and off electrically like field effect transistors (FETs). These two types are coupled in a conjugate manner by sharing electrons. These characteristics make nanotubes an excellent material for making nanometer-sized semiconductor circuits.

Conventional methods of manufacturing nanotubes rely on randomly forming both metal and semiconductor nanotubes. Under conventional methods, carbon nanotube FETs are fabricated from carbon nanotubes grown under ambient conditions. These nanotubes exhibit p-channel conductivity due to oxygen involvement at the metal-carbon nanotube interface (V. Derycke et.
al., Appl. Phys. Lett. 80, 2273, 2002: Non-Patent Document 1). The amount of oxygen at the metal-carbon nanotube interface can be easily changed by standard manufacturing processes (for example, any post-treatment including evacuation, such as thin film deposition). Indeed, p-carbon-nanotube FETs can be easily converted to simultaneous bipolar or n-carbon-nanotube FETs by evacuation.

Conventional methods using gaseous NO ₂ for p-doping carbon nanotubes require the device to be stored in a controlled environment to prevent dopant desorption. Conventional methods for n-channel conductivity for carbon nanotube FETs require annealing / degassing or doping in contact with an electron-donating alkali metal or gas (NH ₃ ) (V. Derycke et al. al.
Appl. Phys. Lett., 80, 2773, 2002). Both require a controlled environment, and the device quickly degrades and fails when exposed to air (J. Kong et. Al., Science, 287, 622, 2000: Non-patent document 2).

Carbon nanotube FETs are known as Schottky barrier (SB) type FETs whose switching is dominated by SB generated at the metal / nanotube interface (J. Appenzeller
et. al., Phys. Rev. Lett., 89, 126801, 2002: Non-Patent Document 3), known to operate as p-type FETs in air (V. Derycke et.
al. Appl. Phys. Lett., 80, 2773, 2002). As the gate dielectric thickness is reduced, due to the quasi-one-dimensional channel of the nanotubes and the very thin carbon nanotube body thickness, SB is well tolerated for thermal tunneling of electrons or holes. The carbon nanotube FETs function as synchronous bipolar FETs in the air because they become so thin. Exponential degradation of OFF current with simultaneous injection of electrons and holes into the channel of carbon nanotubes and increased drain field (defined as leakage current flowing through the transistor when conduction is turned off: M . Radosavljevic
et. al., Appl. Phys. Lett., 83, 2435, 2003: Non-Patent Document 4) is not allowed in small FETs for potential logic gate applications (off current) Is as high as the on-current, and the transistor does not switch off). In addition, the uncontrollability of the conventional carbon nanotube FET manufacturing method results in large fluctuations in the device drive current of the carbon nanotube FETs, and the device threshold potential that is too high for ultimate device miniaturization. It is supposed to be.

  No reliable method is known for producing carbon nanotubes with specific properties. Also known are nanotube separations such as selective synthesis (methods of selectively synthesizing metal nanotubes or semiconductor nanotubes) or post synthesis (methods of isolating metal nanotubes from semiconductor nanotubes or converting semiconductor tubes into metal tubes). It has not been done. In particular, there is no known method for p-doping carbon nanotube FETs.

V. Derycke et. Al. Appl. Phys. Lett., 80, 2773, 2002 J. Kong et.al., Science, 287, 622, 2000 J. Appenzelleret. Al., Phys. Rev. Lett., 89, 126801, 2002 M. Radosavljevicet. Al., Appl. Phys. Lett., 83, 2435, 2003

  Therefore, the drive current is improved, the threshold potential can be reduced / controlled, the minority carrier injection in the off state is suppressed (ie, the change from a simultaneous bipolar transistor to a unipolar transistor) and the ambient There was a need to provide a stable and reliable method for producing stable carbon nanotube FETs.

  One embodiment of the present invention relates to nanostructures, and more particularly to systems and methods for solution processing p-doping of carbon nanotube FETs. The present invention also relates to the formation of carbon nanotube FET devices. In one configuration of the invention, a method for doping carbon nanotubes includes exposing the nanotubes to a one-electron oxidant in a liquid phase. In one embodiment, the concentration of the one-electron oxidant is about 0.01 mM to about 20 mM, and the temperature is about 10 ° C. to about 100 ° C. In one embodiment, the one-electron oxidant is selected from the group comprising an organic one-electron oxidant, an organometallic complex, a pi-electron acceptor and a silver salt. The organic one-electron oxidant is selected from the group comprising trialkyloxonium hexachloroantimonate, antimony pentachloride, nitrosoonium salt, tris- (pentafluorophenyl) borane, and nitrosoonium salt. The organometallic complex includes tris- (2,2′-bipyridyl) cobalt (III) and tris- (2,2′-bipyridyl) ruthenium (II), and the pi-electron acceptor is tetracyanoquinodimethane, It is selected from the group consisting of benzoquinone, tetrachlorobenzoquinone, tetrafluorobenzoquinone, tetracyanoethylene, tetrafluoro-tetracyanoquinodimethane, chloranyl, bromanyl and dichlorodicyanobenzoquinone.

  In another configuration of the invention, a carbon nanotube FET device is provided. The device includes a gate, a gate dielectric deposited on the gate, and a p-doped region of carbon nanotubes on the gate dielectric, wherein the p-doped region is a solution using a one-electron oxidant. Formed by process doping, the source is formed on the first end of the carbon nanotube and the drain is formed on the second end of the carbon nanotube. In another configuration, the device comprises a source formed on the first end of the gate dielectric and a drain formed on the second end of the gate dielectric, wherein the carbon nanotube is a gate dielectric. Disposed on the body and the source and drain. In yet another configuration, the device includes a second dielectric layer deposited on the carbon nanotubes, and a top gate is formed on the second dielectric layer. In yet another configuration, the device is formed on the first doped end of the carbon nanotube and the drain is formed on the second doped end of the carbon nanotube.

  In another configuration of the present invention, a method of forming a carbon nanotube FET device is provided. The method includes the steps of providing a gate, depositing a gate dielectric on the gate, and forming a channel on the gate dielectric that includes a p-doped region of carbon nanotubes. And forming a source on the first end of the carbon nanotube and forming a drain on the second end of the carbon nanotube. It is out. In another configuration of this method, the source is formed on the first end of the gate dielectric, the drain is formed on the second end of the gate dielectric, and the carbon nanotubes are formed on the gate dielectric and the source. And deposited on the drain. In yet another configuration of this method, a second dielectric layer is deposited on the carbon nanotubes, and a top gate is formed on the second dielectric layer. In yet another configuration of the method, a channel is formed on the gate dielectric, a source is formed on the carbon nanotube doped first end, and a drain is formed on the carbon nanotube doped second end. Formed on the part.

  For ease of understanding, the same reference numerals will be used where possible to indicate the same elements common to the drawings.

In a first embodiment, the present invention relates to a method of forming doped carbon nanotubes by solution processing. The carbon nanotubes of the present invention are air stable and exhibit improved device performance in both on and off states. The characteristics of the carbon nanotubes of the present invention are: variability in threshold potential V _th , improvement of I _on about 1 to about 3 orders of magnitude, suppression of minority carrier injection, and in the case of carbon nanotube FETs from the usual SB carbon nanotube FETs. Durability to drain induced I _off degradation, simultaneous bipolar to unipolar conversion of carbon nanotube FET, I _on / I _off ratio of about 10 ² to about 10 ⁷ , and drain induced barrier lowering (DIBL) -like behavior Including, but not limited to. I _on is defined as the current when the transistor is switched on (V _g > V _th ). Normally, I _on is compared under a constant voltage excess (ie, V _g −V _th = constant, eg, around 0.5V).

In accordance with one embodiment of the present invention, a carbon nanotube FET device in which carbon nanotubes are constrained by upper source and drain and doped back gate (eg, silicon) at both ends of a gate dielectric (eg, silicon dioxide). A method for manufacturing is provided. In one embodiment, a source electrode and a drain electrode comprising palladium are used, the source electrode and the drain electrode being about 10 nm to about 5 μm apart on top of about ₂ nm to about 100 nm of SiO ₂ and Si back gate. ing. The nanotubes can be introduced into a solution containing a one-electron oxidant capable of oxidizing aromatic compounds. The p-doping is performed by a reaction between the one-electron oxidant and the aromatic compound on the carbon nanotube to form a charge transfer complex. The interaction between the carbon nanotubes and the charge transfer complex provides a charged (radical cation) atmosphere on the carbon nanotubes.

  Solution processing doping using a one-electron oxidant can be performed in an organic solvent including, but not limited to, dichloromethane, acetonitrile, chloroform, and mixtures thereof. One-electron oxidizing agents that can be used in the solution processing doping of the present invention can include, but are not limited to, organic one-electron oxidizing agents, organometallic complexes, π electron acceptors, and silver salts. Absent. Examples of organic one-electron oxidants include trialkyloxonium hexachloroantimonate, antimony pentachloride, nitrosoonium salts (eg, triethyloxonium tetrafluoroborate), tris- (pentafluorophenyl) borane, and nitrosoonium cations. Can be mentioned. Examples of organometallic complexes include tris- (2,2′-bipyridyl) cobalt (III) and tris- (2,2′-bipyridyl) ruthenium (II). Examples of pi-electron acceptors include tetracyanoquinodimethane, benzoquinone, tetrachlorobenzoquinone, tetrafluorobenzoquinone, tetracyanoethylene, tetrafluoro-tetracyanoquinodimethane, chloranil, tromanyl, bromanyl and dichlorodicyanobenzoquinone. Can do. Examples of silver salts include silver fluoride and silver trifluoroacetate. As the common solvent for the organometallic dopant, acetonitrile, tetrahydrofuran, and aromatic hydrocarbons and chlorine-containing solvents such as dichloromethane and chloroform are suitable. For inorganic salts such as silver fluoride, either alcohol or a mixture of alcohol and water can be used.

In one embodiment, triethyloxonium hexachloroantimonate (C ₂ H ₅ ) ₃ O ⁺ SbCl ₆ ⁻ with a concentration range of about 1-10 mM and a temperature range of about 10-100 ° C. can be used. One exemplary solvent can include acetonitrile. Antimony is considered to react with carbon nanotubes as follows, with “1” as a benzene ring or a plurality of benzene rings on the carbon nanotubes.

本発明の方法に従い、ナノチューブのドーピングは、チャネル材料としてナノチューブを用いるデバイス上で行うことができる。他の方法に従えば、ナノチューブのドーピングはまた、バルク中で行うことができる。いずれの方法によってもｐ−ドープされたカーボンナノチューブは、約１〜２桁の駆動電流の改善、約０．５〜約１Ｖの閾値電位の増加、同時両極性トランジスタの電子電流の抑制、同時両極性からユニポーラへの微小カーボンナノチューブＦＥＴの変更、約１０^２〜約１０^７のＩ_ｏｎ／Ｉ_ｏｆｆ比および優れたＤＩＢＬを示す。

In accordance with the method of the present invention, the doping of the nanotubes can be performed on a device that uses nanotubes as the channel material. According to other methods, the doping of the nanotubes can also be performed in bulk. Either way, p-doped carbon nanotubes can improve driving current by about 1 to 2 digits, increase threshold voltage by about 0.5 to about 1V, suppress electronic current of simultaneous bipolar transistors, From small to unipolar carbon nanotube FETs, an I _on / I _off ratio of about 10 ² to about 10 ⁷ and excellent DIBL.

  Device doping is generally performed by exposing a device containing a single nanotube to an organic solvent solution of a dopant, such as a one-electron oxidant. The concentration of the one-electron oxidant in the organic solution is about 0.01 mM to about 20 mM, and the temperature is about 10 ° C to about 100 ° C. The reaction rate and temperature are controlled to achieve a charge density of about 0.01 electrons to about 1 electron per nm of tube length. Any excess one-electron oxidant on the nanotubes is removed by rinsing the nanotubes in the same or different organic solvent used in the doping process. After rinsing, the device is dried under vacuum.

  In the method of the present invention, bulk doping is performed by stirring a suspension of nanotubes in an organic solvent in an organic solvent solution in the presence of a one-electron oxidant. The concentration of the one-electron oxidant in the organic solution is about 0.01 mM to about 20 mM, and the temperature is about 10 ° C. to about 100 ° C. The reaction rate and temperature are controlled to achieve a charge density of about 0.01 electrons to about 1 electron per nm of tube length. Any excess one-electron oxidant on the nanotubes is removed by rinsing the nanotubes in the same or different organic solvent used in the doping process. After rinsing, the sample, eg, bulk nanotube, is dried under vacuum.

  1-4 show a method of forming an FET according to one embodiment of the present invention. A gate dielectric 120 or high K (melting point) metal such as silicon dioxide or oxynitride is deposited on the gate 100. In one embodiment, the silicon substrate is redundantly doped. The gate dielectric has a thickness of about 1 to about 100 nm. For example, a nanocomponent 140 such as a carbon nanotube is deposited on the gate dielectric 120 by spin coating a solution containing the nanotube. The deposition of carbon nanotubes from liquid suspensions by spin coating is known in the art and solvents can include, for example, dichloroethane, N-methylpyrrolidone, N, N-dimethylformamide, and water. . A resist pattern is then formed on the carbon nanotubes by conventional lithographic techniques. For example, the resist layer can be deposited on the carbon nanotubes 140 and can be patterned using electron beam lithography or photolithography. Using a positive resist, the resist layer exposed to electron beam or lithographic radiation is removed using a developer to give the resist pattern shown in FIG. The resist pattern formed on the carbon nanotube has one or more sections of about 10 nm to about 500 nm when using electron beam lithography and about 500 nm to about 10 μm when using photolithography. ing. The multiple compartments correspond to line-space compartments derived from the respective lithographic techniques and represent the separation between adjacent top gates. The use of multiple top gates provides flexible individual control for different logic applications, eg, AND, OR, NOR operations.

  As shown in FIG. 2, the metal layer 160 has a thickness in the range of about 15 nm to about 50 nm and is deposited to cover a portion of the carbon nanotubes 140 on the resist pattern. The metal can be Pd, Ti, W, Au, Co, Pt, or alloys or metal nanotubes thereof. If metal nanotubes are used, the metal layer 160 can include one or more metal nanotubes. Other metals or alloys such as Pd, Ti, W, Au, Co, Pt can be deposited by electron beam or evaporation under vacuum, while metal nanotubes should be deposited by solution phase techniques such as spin coating. Can do. After metal deposition, the structure can be immersed in acetone or N-methylpyrrolidone (NMP) to strip the resist. This process removes the lithographically patterned resist and the metal deposited on the top layer by immersing the sample in a solvent such as acetone or NMP. For the purposes of this specification, the solvents described above are also referred to generically as resist stripping components. The metal portions 162 and 164 (shown in FIG. 3) remaining on the carbon nanotubes 140 form the source and drain of the FET. In this embodiment, the source and drain are formed covering the carbon nanotubes 140, more generally the first and second regions of the nanocomponent 140, respectively.

  After stripping the resist, the structure having the carbon nanotubes 140 shown in FIG. 3 is immersed in an organic solution containing the preferred one-electron oxidant described above. FIG. 4 shows the doping molecules bound to the carbon nanotubes 140. The doped portion of carbon nanotube 140 (between the metal source and drain) functions as the channel of the FET.

  FIG. 5 shows another embodiment of a carbon nanotube FET. A gate 100, in this embodiment, a silicon dioxide or oxynitride stack, or a high-K metal layer gate dielectric 120, about 1 nm to about 100 nm thick, is deposited on the overdoped silicon substrate. Yes. Metal portions 162, 164 are then formed on gate dielectric 120 using a resist stripping process (not shown) similar to that described above with respect to FIGS. Metal portions 162, 164 having a thickness of about 15 nm to about 300 nm form the source and drain of the FET. The metal can be Pd, Ti, W, Au, Co, Pt or an alloy thereof or one or more metal nanotubes. Carbon nanotubes 140 are then deposited on the gate dielectric 120 and metal portions 162,164. Blanket doping of the carbon nanotubes 140 is accomplished by immersing in an organic solution containing a suitable one-electron oxidant. The doping molecules bind to the carbon nanotubes as described herein. In the illustrated example, the portion of the carbon nanotube 140 in contact with the gate dielectric 120 forms the FET channel. Alternatively, the carbon nanotubes 140 can be selectively doped through a patterned resist formed on the carbon nanotubes 140. The patterned resist can be formed, for example, by depositing a suitable resist material on the carbon nanotubes 140 and patterning using conventional lithographic techniques. In one embodiment, hydrogen silsesquioxane (HSQ), which can be used as a negative resist, can be used for this purpose.

  FIG. 6 shows a dual gate carbon nanotube FET including a top gate. In this embodiment, a silicon dioxide or oxy-nitride stack, or a high-K metal layer gate dielectric 120, about 1 nm to about 100 nm thick is deposited on a gate 100 consisting of an overdoped silicon substrate. ing. On the gate dielectric 120, carbon nanotubes 140 are deposited, for example, by spin coating. The metal portions 162, 164 are formed on the carbon nanotubes 140 using the resist stripping technique described in connection with FIGS. After the formation of the metal portions 162, 164 (which function as the source and drain of the FET), the structure including the carbon nanotubes 140 and the metal portions 162, 164 can be made of low-temperature oxide (LTO) or CVD high K dielectric ( For example, it is covered by a dielectric layer 180 such as a hafnium dioxide layer. The top gate 200 includes metal or highly doped polysilicon and is formed on top of the dielectric layer 180. Using the top gate 200 as an etching mask, the dielectric layer 180 is etched to leave only the portion immediately below the top gate 200. For example, diluted hydrofluoric acid (eg, 100: 1 HF) can be used as an etchant for LTO. This device is doped in a dopant solution to achieve partial doping of the carbon nanotubes 140. The doping molecules are bonded to the carbon nanotubes as described above. In this case, the channel consists of both a gated undoped region and two doped regions. The doped region functions to be on the extension of the CMOS FET, reduces the contact barrier, and improves the drive current and transistor switching properties. The device can be operated by either the top (or front) gate or the back gate, or both. In logic applications, it is preferable to drive the FET as a top gate configuration for good AC characteristics.

  7-9 show another embodiment of the FET. In one embodiment, a silicon dioxide or oxy-nitride stack, or a high-K metal layer gate dielectric 120, about 1 nm to about 100 nm thick is deposited on a gate 100 composed of an overdoped silicon substrate. Has been. On the gate dielectric 120, carbon nanotubes 140 are deposited, for example, by spin coating. The patterned resist is formed on the carbon nanotubes 140 using conventional lithography techniques such as electron beam or photolithography. The structure containing the patterned resist and carbon nanotubes 140 is immersed in an organic solvent containing a suitable one-electron organic dopant. Doping molecules bind to the exposed portions of the carbon nanotubes 140. After doping, a metal layer 160 having a thickness of about 15 nm to about 50 nm is deposited on the patterned resist and doped carbon nanotubes 140. The metal can be Pd, Ti, W, Au, Co, Pt or an alloy thereof or one or more metal nanotubes, for example as described above using electron beam or thermal evaporation or spin coating. Can be deposited as follows. After metal deposition, the structure shown in FIG. 8 is resist stripping, which is a process of immersing a sample in acetone or NMP with lithographically patterned resist and metal deposited on top into acetone or NMP. Soaked for. As shown in FIG. 9, the metal portions 162, 164 left after stripping form the source and drain of the FET. The process of FIGS. 7-9 creates significant doping profile differences along the channel of the carbon nanotube transistor. In this case, the undoped portion of the carbon nanotube 140 forms a channel of the FET.

  To complete the formation of the FET device of FIGS. 1-4, is the device coated with an organic material such as PMMA (poly (methyl methacrylate)) or HSQ (hydrogensilsesquioxane, low K dielectric layer)? Or by depositing a low temperature film-like silicon dioxide dielectric film. Further processing of the device is accomplished by metallization for the line back end.

Referring to FIG. 10, SbCl ₆ ^- shows a schematic diagram of a carbon nanotube FET500 doped with counter ions 510. For example, the ^{_{dopant, (C 2 H 5) 3}} O + SbCl 6 - and it can be, SbCl ₆ ^- counter ions are bound to electrostatically carbon _{nanotubes, C 2 H 5 Cl, (} C 2 H ₅ ) ₂ O and SbCl ₃ are removed as volatile products (not shown).

Referring to FIG. 11, a typical transport property (I _d vs. V _gs ) at Vsd = −0.5 V of a carbon nanotube FET before and after doping with (C ₂ H ₅ ) ₃ O ⁺ SbCl ₆ ⁻ is shown. ing. In this example, the doping is a solution at about 50 ° C. containing (C ₂ H ₅ ) ₃ O ⁺ SbCl ₆ ⁻ at a concentration of about 1-10 mM in a device containing carbon nanotubes dissolved in acetonitrile (eg, solvent). In for about 12 hours. It will be appreciated that different process conditions can also be used depending on the particular dopant and the desired device characteristics, for example, a concentration of about 0.01 mM to about 20 mM, and a temperature of about 10 ° C. to about 100 ° C. . V _th for hole conduction increases from −1.55 V (original carbon nanotube FET) to −0.85 V, which is an electron from the nanotube to the dopant (C ₂ H ₅ ) ₃ O ⁺ SbCl ₆ ⁻ . This shows that the migration occurred, the Fermi level EF of the nanotube was moved to the coupling band side, and _Vth was adjusted to an appropriate gate bias region. The drive current I _on was improved by two orders of magnitude, greatly reducing the contact resistance between the tube and the metal. After doping, injection of minority carriers (electron current) at the drain was suppressed, and the carbon nanotube FET was converted from simultaneous bipolar to unipolar. Simultaneous bipolar is understood as meaning that both carriers (electrons and holes) participate in channel conduction and unipolar means that one type of carrier participates in channel conduction.

Referring to FIG. 12, the I _d -V _gs characteristics of the doped device described above at various V _ds (from −0.1 to −0.5 V in −0.1 V increments) are shown. Complete suppression of the drain electric field induced minority carrier injection and induced a drain induced barrier lowering (DIBL) -like behavior. This suggests that the affinity / adsorption of dopant to the metal contact / tube interface may be stronger. This can be attributed to the fact that the dopant is more aggregated to the nanotube / metal interface, causing strong band bending and suppressing the injection of minority carriers (electrons) in the off state. The reduced amount of subthreshold S = dV _gs / d (log I _d ) from 120 mV to 85 mV / decade (I _d −V _g after doping) improves carbon nanotube channel switching and excellent gate control. It is shown.

FIG. 13 shows the output characteristics (I _d vs. V _ds ) of the p-doped device described above. Its transconductance g _m (dI _d / dV _g ) at V _ds = −1.32 V is 2 uS, indicating the superior performance of p-CNFET with small diameter carbon nanotubes using a gate dielectric. is there. The device is stable for several weeks in air and preserves the doping properties after solvent cleaning and evacuation. Furthermore, the absorption of dopants by the device of the present invention was irreversible.

  The structures shown in the drawings of the present invention are not drawn to scale. That is, the various structures are described as exemplary embodiments. Accordingly, the length, height, and width of the various structures shown in the drawings should not be construed as limiting the invention.

Schematic of FET formation process. Schematic of FET formation process. Schematic of FET formation process. Schematic of FET formation process. Schematic of another embodiment of a carbon nanotube FET. Schematic of dual gate carbon nanotube FET. The figure which showed another embodiment of FET. The figure which showed another embodiment of FET. The figure which showed another embodiment of FET. SbCl ₆ ^- schematic view of a carbon nanotube FET doped with counter ions. ^{_{(C 2 H 5) 3 O}} + SbCl 6 - carbon nanotube FET before and after doping with, shows the transport properties of _{Vds = -0.5V (I d vs.V gs} ). ^{_{(C 2 H 5) 3 O}} + SbCl 6 - after doping with, shows the _I d _{-V gs} characteristics at various _{V ds} of the device (up to -0.1 0.5 0. 1V increments). p- doped device output characteristics _(I d _{vs.V ds)} shows a.

Explanation of symbols

100 ... gate, 120 ... gate dielectric 140 ... carbon nanotube, 160 ... metal layer, 162, 164 ... metal part, 180 ... dielectric layer, 200 ... top gate, 500 ... carbon nanotube FET, 510 ... SbCl ₆ ^- Counter ion

Claims (27)

  A method of doping carbon nanotubes, the method comprising exposing the carbon nanotubes to a one-electron oxidant in solution.   The method according to claim 1, wherein the concentration of the one-electron oxidizing agent is 0.01 mM to 20 mM.   The method according to claim 2, wherein the one-electron oxidant is selected from at least one of an organic one-electron oxidant, an organometallic complex, a π-electron acceptor, and a silver salt.   The organic one-electron oxidant is selected from at least one of trialkyloxonium hexachloroantimonate, antimony pentachloride, nitrosoonium salt, triethyloxonium tetrafluoroborate, tris- (pentafluorophenyl) borane, and nitrosoonium cation. 4. The method of claim 3, wherein:   4. The organometallic complex according to claim 3, wherein the organometallic complex is selected from at least one of tris- (2,2'-bipyridyl) cobalt (III) and tris- (2,2'-bipyridyl) ruthenium (II). Method.   The π electron acceptor is selected from at least one of tetracyanoquinodimethane, benzoquinone, tetrachlorobenzoquinone, tetrafluorobenzoquinone, tetracyanoethylene, tetrafluoro-tetracyanoquinodimethane, chloranil, bromanyl and dichlorodicyanobenzoquinone. 4. The method of claim 3, wherein:   The method of claim 3, wherein the silver salt is silver fluoride. A carbon nanotube field effect transistor (FET) comprising:
The gate,
A gate dielectric deposited on the gate;
Carbon nanotubes comprising at least one doped region formed on the gate dielectric and formed by solution doping with a one-electron oxidant;
A source formed on a first end of the carbon nanotube;
A carbon nanotube field effect transistor comprising: a drain formed on a second end of the carbon nanotube.   The carbon nanotube field effect transistor of claim 8, wherein the at least one doped region is a p-doped region.   The carbon nanotube field effect transistor of claim 8, wherein the at least one doped region provides a channel for the FET. And a dielectric layer deposited on the carbon nanotubes;
The carbon nanotube field effect transistor of claim 8, comprising: a top gate deposited on the dielectric layer.   The carbon nanotube field effect transistor of claim 11, wherein at least the one doped region of the carbon nanotube includes a doped region that does not contact the dielectric layer or the source or the drain.   The at least one doped region includes two doped regions, the source is deposited on one of the doped regions, and the drain is deposited on another one of the doped regions. Item 9. The carbon nanotube field effect transistor according to Item 8. A carbon nanotube field effect transistor (FET) comprising:
The gate,
A gate dielectric deposited on the gate;
A source formed on a first end of the gate dielectric;
A drain formed on the second end of the gate dielectric;
A carbon nanotube field effect transistor comprising carbon nanotubes deposited on the source, the drain, and the gate dielectric, the carbon nanotubes being doped by solution processing doping with a one-electron oxidant.   The carbon nanotube field effect transistor of claim 14, wherein the doped carbon nanotube is a p-doped region.   The carbon nanotube field effect transistor of claim 14, wherein the portion of the doped carbon nanotube provides a channel for the FET. A method for forming a carbon nanotube field effect transistor (FET) comprising:
Providing a gate;
Depositing a gate dielectric on the gate;
Forming a carbon nanotube comprising at least one doped region formed by solution processing doping with a one-electron oxidant on the gate dielectric;
Forming a source on a first end of the carbon nanotube;
Forming a drain on the second end of the carbon nanotube.   The method of claim 17, wherein the at least one doped region is a p-doped region. The steps of forming the source and forming the drain include
Providing a resist layer on the carbon nanotube;
Depositing a metal layer on the resist layer;
The method according to claim 17, further comprising: applying a resist stripping component to the metal layer to form the drain and the source. And depositing a dielectric layer on the carbon nanotubes;
And depositing a top gate on the dielectric layer.     21. The method of claim 20, wherein at least the one doped region of the carbon nanotube includes a doped region that does not contact the dielectric layer or the source or drain. The steps of forming the source and forming the drain include
Providing a resist layer on the carbon nanotube;
Depositing a metal layer on the resist layer;
21. A method according to claim 20, comprising: applying a resist stripping component to the metal layer to form the drain and the source.   The at least one doped region includes two doped regions, the source is deposited on one of the doped regions, and the drain is deposited on another one of the doped regions. Item 18. The method according to Item 17. The steps of forming the source and forming the drain include
Providing a resist layer on the carbon nanotube;
Contacting the carbon nanotube with a solution of the one-electron oxidant;
Depositing a metal layer on the resist layer;
24. A method according to claim 23, comprising: applying a resist stripping component to the metal layer to form the drain and the source. A method of forming a carbon nanotube field effect transistor (FET) comprising:
Providing a gate;
Depositing a gate dielectric on the gate;
Forming a source on a first end of the gate dielectric;
Forming a drain on the second end of the gate dielectric;
Forming carbon nanotubes that are entirely doped by solution treatment doping with a one-electron oxidant on the source, the drain, and the gate dielectric.   26. The method of claim 25, wherein the doped carbon nanotube is p-doped. The steps of forming the source and forming the drain include
Providing a resist layer on the gate dielectric;
Depositing a metal layer on the resist layer;
The method according to claim 25, comprising: applying a resist stripping component to the metal layer to form the drain and the source.

Images