tunneling transistor

Abstract

A tunneling transistor includes: a gate; an insulating layer disposed on the surface of the gate; a single carbon nanotube disposed on the surface of the insulating layer away from the gate, the single carbon nanotube being a semiconducting carbon nanotube; a film structure directly contacting a portion of the single carbon nanotube, the film structure being a molybdenum disulfide film or a tungsten disulfide film; a source electrode electrically connected to the film structure; and a drain electrode electrically connected to the single carbon nanotube.

Description

Technical Field

[0001] This invention relates to a tunneling transistor. Background Technology

[0002] Carbon nanotubes possess excellent mechanical and chemical properties, and their length of up to 1 micrometer, along with the advent of transistors, facilitated the birth of integrated circuits. With the continuous development of integrated circuits, the development of semiconductor transistors has moved in two different directions: one is to shrink the size of transistors, and the other is to improve the high-frequency performance of transistors.

[0003] Tunneling transistors (TTTs) are a novel type of high-speed device that utilizes the quantum tunneling effect. As an important member of the nanoelectronics family, TTTs have seen faster and more mature development compared to other nanodevices (such as single-electron devices and quantum dot devices), and have already begun to enter the application stage. TTTs are characterized by high-frequency, high-speed operation, low operating voltage, and low power consumption.

[0004] Carbon nanotubes can be viewed as one-dimensional tubular nanomaterials formed by rolling up layers of graphite. Due to their strong interatomic bonding and unique atomic arrangement, carbon nanotubes exhibit excellent properties and broad application prospects in many aspects, including mechanical, thermal, optical, and electrical properties. Therefore, applying carbon nanotubes to tunneling transistors is a developing trend. Summary of the Invention

[0005] In view of this, it is indeed necessary to provide a tunneling transistor that uses semiconducting carbon nanotubes, which has a high on-current and a low subthreshold swing.

[0006] A tunneling transistor includes a gate, an insulating layer, a source, and a drain. The insulating layer is disposed on the surface of the gate. The tunneling transistor further includes a single carbon nanotube and a film structure. The single carbon nanotube is disposed on the surface of the insulating layer away from the gate, and the single carbon nanotube is a semiconducting carbon nanotube. The film structure directly contacts a portion of the single carbon nanotube, and the film structure is a molybdenum disulfide film or a tungsten disulfide film. The source is electrically connected to the film structure, and the drain is electrically connected to the single carbon nanotube.

[0007] Compared with the prior art, the tunneling transistor provided by the present invention contains both p-type and n-type single semiconductor carbon nanotubes, allowing electrons to tunnel from the p-type valence band to the n-type conduction band, thus achieving interband tunneling; and there is an ideal interface with strong coupling between the one-dimensional single semiconductor carbon nanotube and the two-dimensional MoS2 film (or WS2 film), which can improve the conduction current and reduce the subthreshold swing. Attached Figure Description

[0008] Figure 1 This is a process flow diagram of the method for n-type doping of carbon nanotubes provided in the first embodiment of the present invention.

[0009] Figure 2 This is a schematic diagram of a structure provided in the first embodiment of the present invention, showing a portion of a single carbon nanotube covered and in direct contact with a MoS2 or WS2 membrane.

[0010] Figure 3 This is a schematic diagram of the structure provided in the first embodiment of the present invention, showing that the MoS2 or WS2 film covers and directly contacts the entire upper surface of a single carbon nanotube.

[0011] Figure 4 A process flow diagram of another method for n-type doping of carbon nanotubes provided in the second embodiment of the present invention.

[0012] Figure 5 This is a cross-sectional schematic diagram of the first carbon nanotube composite structure provided in the third embodiment of the present invention.

[0013] Figure 6 This is a cross-sectional schematic diagram of the second carbon nanotube composite structure provided in the third embodiment of the present invention.

[0014] Figure 7 This is a cross-sectional schematic diagram of the third carbon nanotube composite structure provided in the third embodiment of the present invention.

[0015] Figure 8 This is a top view schematic diagram of the fourth carbon nanotube composite structure provided in the third embodiment of the present invention.

[0016] Figure 9 This is a top view schematic diagram of the fifth carbon nanotube composite structure provided in the third embodiment of the present invention.

[0017] Figure 10 This is a top view of the sixth carbon nanotube composite structure provided in the third embodiment of the present invention.

[0018] Figure 11 This is a schematic diagram of the back-gate tunneling transistor provided in the fourth embodiment of the present invention.

[0019] Figure 12 This is a three-dimensional structural diagram of a back-gate tunneling transistor provided in the fourth embodiment of the present invention.

[0020] Figure 13 The current scan diagram of the back-gate tunneling transistor, expressed in logarithmic form, is provided for the fourth embodiment of the present invention.

[0021] Figure 14 The transfer characteristic curve of the back-gate tunneling transistor provided in the fourth embodiment of the present invention.

[0022] Figure 15 The typical output characteristic curve of the back-gate tunneling transistor in BTBT operating mode provided in the fourth embodiment of the present invention is shown.

[0023] Figure 16 The typical output characteristic curve of the back-gate tunneling transistor in pn junction operating mode provided in the fourth embodiment of the present invention.

[0024] Figure 17 The typical output characteristic curve of the back-gate tunneling transistor in the nn junction operating mode provided in the fourth embodiment of the present invention is shown.

[0025] Figure 18 The transfer characteristic curves of the back-gate tunneling transistor and the individual carbon nanotube transistor provided in the fourth embodiment of the present invention are shown.

[0026] Figure 19 The photocurrent diagram of the back-gate tunneling transistor provided in the fourth embodiment of the present invention.

[0027] Figure 20 The energy band diagram of the back-gate tunneling transistor provided in the fourth embodiment of the present invention before the contact between the semiconducting carbon nanotube and the MoS2 film.

[0028] Figure 21 The energy band diagram of the semiconductor carbon nanotube and MoS2 film of the back-gate tunneling transistor provided in the fourth embodiment of the present invention after contact.

[0029] Figure 22 The transfer characteristic curves of the back-gate tunneling transistor provided in the fourth embodiment of the present invention at different temperatures.

[0030] Figure 23 From Figure 22 The subthreshold swings extracted in the diffusion region and BTBT region.

[0031] Figure 24 Typical output curves of the CNT-MoS2 heterostructure in the back-gate tunneling transistor under different gate voltages in BTBT operating mode, plotted on a semi-logarithmic scale according to the fourth embodiment of the present invention.

[0032] Figure 25 This is the energy band diagram of a reverse rectifier diode under reverse bias.

[0033] Figure 26 This is the energy band diagram of a Zener diode under reverse bias.

[0034] Figure 27 The output curve is the temperature-dependent curve of the BTBT state when Vg = 20V.

[0035] Figure 28 The inverse slope of the inter-band tunneling current (BTBT current) and forward bias current with respect to temperature when Vg = 20V.

[0036] Figure 29 The source-drain current I at a temperature of 130K ds Image.

[0037] Figure 30 The figures show the transfer characteristic curves of a simple metallic carbon nanotube field-effect transistor and a metallic carbon nanotube field-effect transistor covered with a MoS2 film.

[0038] Figure 31 This is a schematic diagram of the top-gate tunneling transistor provided in the fifth embodiment of the present invention.

[0039] Figure 32 The process flow diagram is provided for the p-type doping method of carbon nanotubes according to the sixth embodiment of the present invention.

[0040] Figure 33 This is a schematic diagram of a structure provided in the sixth embodiment of the present invention, in which a portion of a single carbon nanotube is covered and directly contacts a tungsten diselenide (WSe2) film or a black phosphorus (BP) film.

[0041] Figure 34 This is a schematic diagram of a structure provided in the sixth embodiment of the present invention, in which a tungsten diselenide (WSe2) film or a black phosphorus (BP) film covers and directly contacts the entire upper surface of a single carbon nanotube.

[0042] Figure 35 The transfer characteristic curves are shown for a carbon nanotube field-effect transistor coated with a WSe2 film and a pure carbon nanotube field-effect transistor.

[0043] Figure 36 The process flow diagram is provided for the p-type doping method of carbon nanotubes according to the seventh embodiment of the present invention.

[0044] Explanation of main component symbols

[0045] Single carbon nanotube 12

[0046] Membrane structure 14

[0047] First carbon nanotube composite structure 10

[0048] Second carbon nanotube composite structure 20

[0049] Third carbon nanotube composite structure 30

[0050] Fourth carbon nanotube composite structure 40

[0051] Fifth carbon nanotube composite structure 50

[0052] The sixth carbon nanotube composite structure 60

[0053] Back-gate tunneling transistor 100

[0054] Insulating substrate 102

[0055] Gate 104

[0056] Insulation layer 106

[0057] Source 108

[0058] Drain 109

[0059] Top-gate tunneling transistor 200

[0060] Layered structure 16

[0061] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0062] The tunneling transistor provided by the present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0063] Please see Figure 1 The first embodiment of the present invention provides a method for n-type doping of carbon nanotubes, which includes the following steps:

[0064] S11 provides a single carbon nanotube 12;

[0065] S12, providing a film structure 14, which is a molybdenum disulfide (MoS2) film or a tungsten disulfide (WS2) film; and

[0066] S13, the membrane structure 14 is brought into direct contact with at least a portion of the single carbon nanotube 12.

[0067] In step S11, the single carbon nanotube 12 is a one-dimensional tubular structure. The carbon nanotube can be a metallic carbon nanotube or a semiconducting carbon nanotube. The carbon nanotube includes one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes. The diameter and length of the carbon nanotube are not limited, as long as the carbon nanotube is partially covered by the MoS2 film while the remaining portion is not covered by the MoS2 film. The length of the carbon nanotube can be greater than 50 micrometers. The diameter of the single-walled carbon nanotube is 0.5 nanometers to 50 nanometers, the diameter of the double-walled carbon nanotube is 1.0 nanometers to 50 nanometers, and the diameter of the multi-walled carbon nanotube is 1.5 nanometers to 50 nanometers. In this embodiment, the carbon nanotube is a single-walled carbon nanotube or a double-walled carbon nanotube.

[0068] In step S12, both the molybdenum disulfide (MoS2) film and the tungsten disulfide (WS2) film are two-dimensional film structures 14. The material of the MoS2 film is MoS2, and the material of the WS2 film is WS2. The thickness of the molybdenum disulfide (MoS2) film and the tungsten disulfide (WS2) film is not limited. In this embodiment, the film structure 14 is a molybdenum disulfide (MoS2) film with a thickness of 4.2 nm.

[0069] In step S13, the single carbon nanotube 12 can be completely covered by the MoS2 film or the WS2 film, or it can be partially covered by the MoS2 film or the WS2 film. That is, the MoS2 film or the WS2 film can cover and directly contact a portion of the single carbon nanotube 12, while the other portion of the single carbon nanotube 12 is exposed. The MoS2 film or the WS2 film can also cover and directly contact the entire single carbon nanotube 12. All carbon nanotube portions covered by the MoS2 film or the WS2 film are in direct contact with the MoS2 film or the WS2 film. That is, the MoS2 film or the WS2 film can directly contact a portion of the single carbon nanotube 12, or it can directly contact the entire single carbon nanotube 12. Figure 2 As shown, the MoS2 film or the WS2 film covers and directly contacts a portion of the single carbon nanotube 12. Figure 3 As shown, the MoS2 film or the WS2 film covers and directly contacts the entire upper surface of the single carbon nanotube 12.

[0070] The portion of the single carbon nanotube 12 that is in direct contact with the MoS2 film or the WS2 film is defined as the contact portion, and the portion of the single carbon nanotube 12 that is not in direct contact with the MoS2 film or the WS2 film is defined as the exposed portion. That is, the single carbon nanotube 12 consists of a contact portion and an exposed portion.

[0071] The carbon nanotubes themselves are p-type. The contact portion of the single carbon nanotube 12 changes from p-type to n-type because the MoS2 film or the WS2 film directly contacts the contact portion, and MoS2 or WS2 contributes electrons to the contact portion; that is, electrons enter the contact portion from MoS2 or WS2. The exposed portion of the single carbon nanotube 12 remains p-type because the MoS2 film or the WS2 film does not directly contact the exposed portion, and MoS2 or WS2 does not contribute electrons to the exposed portion.

[0072] Please see Figure 4 The second embodiment of the present invention provides a method for n-type doping of carbon nanotubes, which includes the following steps:

[0073] S21, providing multiple spaced single carbon nanotubes 12;

[0074] S22, providing a membrane structure 14, which is a molybdenum disulfide (MoS2) membrane or a tungsten disulfide (WS2) membrane; and

[0075] S23, the MoS2 film or the WS2 film simultaneously covers the plurality of single carbon nanotubes 12, and at least a portion of each single carbon nanotube 12 directly contacts the MoS2 film or the WS2 film.

[0076] The method for n-type doping of carbon nanotubes provided in the second embodiment is similar to the method for n-type doping of carbon nanotubes provided in the first embodiment, except that: in the first embodiment, a molybdenum disulfide (MoS2) film or a tungsten disulfide (WS2) film covers at least a portion of a single carbon nanotube 12; in the second embodiment, a molybdenum disulfide (MoS2) film or a tungsten disulfide (WS2) film simultaneously covers at least a portion of multiple spaced single carbon nanotubes 12.

[0077] In step S21, the extension directions of the multiple spaced individual carbon nanotubes 12 are parallel to each other.

[0078] In step S23, the MoS2 film or the WS2 film can simultaneously cover a portion of multiple individual carbon nanotubes 12, thereby transforming a portion of each individual carbon nanotube 12 into an n-type. Alternatively, the MoS2 film or the WS2 film can simultaneously cover the entirety of multiple individual carbon nanotubes 12, thereby transforming all of each individual carbon nanotube 12 into an n-type.

[0079] The n-type doping method for carbon nanotubes provided in the first and second embodiments has the following advantages: First, the MoS2 film or the WS2 film directly contacts a portion of a single carbon nanotube 12, which can transform this portion from p-type to n-type, that is, n-type doping is achieved on the single carbon nanotube 12; Second, a portion of the single carbon nanotube 12 can be p-type and another portion can be n-type, that is, the single carbon nanotube 12 contains both p-type and n-type; Third, multiple single carbon nanotubes 12 can be n-doped simultaneously; Fourth, the method is simple and the n-type doping effect is good.

[0080] The third embodiment of the present invention provides a carbon nanotube composite structure, which is prepared by the methods provided in the first and second embodiments.

[0081] Please see Figures 5 to 10 The carbon nanotube composite structure includes at least one single carbon nanotube 12 and at least one membrane structure 14, wherein the membrane structure 14 is the MoS2 membrane or the WS2 membrane.

[0082] When there is only one single carbon nanotube 12, a film structure 14 is disposed on the outer surface of the single carbon nanotube 12 and is in direct contact with a portion of the single carbon nanotube 12. That is, a portion of the single carbon nanotube 12 is in direct contact with the film structure 14, not the entire outer surface of the single carbon nanotube 12.

[0083] When there are multiple individual carbon nanotubes 12, the multiple individual carbon nanotubes 12 are spaced apart, and the at least one film structure 14 is disposed on the outer surface of the at least one individual carbon nanotube 12 and is in direct contact with a portion of each individual carbon nanotube 12. Preferably, the extension directions of the multiple individual carbon nanotubes 12 are parallel to each other. That is, a portion of each individual carbon nanotube 12 is in direct contact with the film structure 14, not the entire outer surface of each individual carbon nanotube 12 is in direct contact with the film structure 14.

[0084] The single carbon nanotube 12 includes at least one p-type portion and at least one n-type portion, and the p-type portion and the n-type portion are alternately arranged. The p-type portion is the exposed portion, and the n-type portion is the contact portion. That is, the single carbon nanotube 12 contains both p-type and n-type. The film structure 14 is disposed on the single carbon nanotube 12, and the film structure 14 is in direct contact with the n-type portion. Further, the outer surface of all n-type portions is in direct contact with a film structure 14. In this embodiment, the film structure 14 is only disposed on the n-type portion of the single carbon nanotube 12, and is in direct contact with the n-type portion. The following uses the first carbon nanotube composite structure 10 to the sixth carbon nanotube composite structure 60 as examples to specifically describe the carbon nanotube composite structure.

[0085] like Figure 5 As shown, the first carbon nanotube composite structure 10 consists of a single carbon nanotube 12 and a membrane structure 14. The single carbon nanotube 12 consists of a p-type portion and an n-type portion. The membrane structure 14 covers the n-type portion and is in direct contact with the outer surface of the n-type portion.

[0086] like Figure 6 As shown, the second carbon nanotube composite structure 20 consists of a single carbon nanotube 12 and a film structure 14. The single carbon nanotube 12 comprises a first p-type portion, a second p-type portion, and an n-type portion, with the n-type portion located between the first p-type portion and the second p-type portion; that is, the single carbon nanotube 12 is pnp type. A film structure 14 covers the n-type portion and is in direct contact with the outer surface of the n-type portion.

[0087] like Figure 7 As shown, the third carbon nanotube composite structure 30 consists of a single carbon nanotube 12 and two film structures 14. The single carbon nanotube 12 comprises a first n-type portion, a second n-type portion, and a p-type portion, with the p-type portion located between the first n-type portion and the second n-type portion; that is, the single carbon nanotube 12 is npn-type. One film structure 14 covers the first n-type portion and is in direct contact with its outer surface, and the other film structure 14 covers the second n-type portion and is in direct contact with its outer surface.

[0088] like Figure 8 As shown, the fourth carbon nanotube composite structure 40 consists of a plurality of parallel and spaced single carbon nanotubes 12 and a film structure 14. Each single carbon nanotube 12 includes a p-type portion and an n-type portion. The film structure 14 simultaneously covers the n-type portions of the plurality of single carbon nanotubes 12 and is in direct contact with the outer surface of the n-type portion.

[0089] like Figure 9 As shown, the fifth carbon nanotube composite structure 50 consists of multiple parallel and spaced-apart single carbon nanotubes 12 and a film structure 14. Each single carbon nanotube 12 includes a first p-type portion, a second p-type portion, and an n-type portion, with the n-type portion located between the first p-type portion and the second p-type portion; that is, each single carbon nanotube 12 is pnp type. The film structure 14 simultaneously covers the n-type portions of the multiple single carbon nanotubes 12 and is in direct contact with the outer surface of the n-type portions.

[0090] like Figure 10 As shown, the sixth carbon nanotube composite structure 60 consists of multiple parallel and spaced-apart single carbon nanotubes 12 and two film structures 14. Each single carbon nanotube 12 includes a first n-type portion, a second n-type portion, and a p-type portion, with the p-type portion located between the first n-type portion and the second n-type portion; that is, each single carbon nanotube 12 is npn-type. One film structure 14 simultaneously covers the first n-type portions of the multiple single carbon nanotubes 12 and is in direct contact with the outer surface of the first n-type portion. The other film structure 14 simultaneously covers the second n-type portions of the multiple single carbon nanotubes 12 and is in direct contact with the outer surface of the second n-type portion.

[0091] Furthermore, the individual carbon nanotubes 12 in the carbon nanotube composite structure can also be of various types such as npnp type and pnpn type. Regardless of how many n-type parts there are in the individual carbon nanotube 12, the outer surface of all n-type parts is in direct contact with the film structure 14.

[0092] It is understood that the first carbon nanotube composite structure 10, the second carbon nanotube composite structure 20 and the third carbon nanotube composite structure 30 are prepared by the method provided in the first embodiment, and the fourth carbon nanotube composite structure 40, the fifth carbon nanotube composite structure 50 and the sixth carbon nanotube composite structure 60 are prepared by the method provided in the second embodiment.

[0093] The carbon nanotube composite structure provided in the third embodiment has the following advantages: First, a portion of the single carbon nanotube 12 is p-type and the other portion is n-type, that is, the single carbon nanotube 12 contains both p-type and n-type; Second, the single carbon nanotube 12 can be of various types such as npn-type, pnp-type, npnp-type, and pnpn-type; Third, since the single carbon nanotube 12 contains both p-type and n-type, when the single carbon nanotube 12 is a semiconducting carbon nanotube, electrons can tunnel from the valence band of the p-type to the conduction band of the n-type, that is, band-to-band tunneling (BTBT) is realized.

[0094] Please see Figure 11 The fourth embodiment of the present invention provides a back-gate tunneling transistor 100, which includes a single carbon nanotube 12, a film structure 14, a source 108, a drain 109, an insulating layer 106, and a gate 104. The back-gate tunneling transistor 100 can be formed on the surface of an insulating substrate 102. The single carbon nanotube 12 is a semiconducting carbon nanotube. The film structure 14 is a molybdenum disulfide (MoS2) film or a tungsten disulfide (WS2) film, wherein the material of the MoS2 film is MoS2, and the material of the WS2 film is WS2.

[0095] The gate electrode 104 is disposed on the surface of the insulating substrate 102. The insulating layer 106 is disposed on the surface of the gate electrode 104 away from the insulating substrate 102. The single carbon nanotube 12 is disposed on the surface of the insulating layer 106 away from the gate electrode 104. The film structure 14 covers and directly contacts a portion of the single carbon nanotube 12, and the single carbon nanotube 12 is located between the insulating layer 106 and the film structure 14. The source electrode 108 is electrically connected to the film structure 14, and the drain electrode 109 is electrically connected to the single carbon nanotube 12. The insulating layer 106 is located between the source electrode 108 and the gate electrode 104, and between the drain electrode 109 and the gate electrode 104. In this embodiment, the source electrode 108 is in direct contact with the film structure 14, and the drain electrode 109 is in direct contact with the single carbon nanotube 12. Since the single carbon nanotube 12 is one-dimensional and the membrane structure 14 is two-dimensional, a portion of the membrane structure 14 is in direct contact with the single carbon nanotube 12, and a portion is in direct contact with the insulating layer 106. A portion of the single carbon nanotube 12 is located between the membrane structure 14 and the insulating layer 106, and is in direct contact with both the membrane structure 14 and the insulating layer 106.

[0096] The insulating substrate 102 serves a supporting function, and its material can be selected from rigid materials such as glass, quartz, ceramic, diamond, and silicon wafers, or flexible materials such as plastics and resins. In this embodiment, the insulating substrate 102 is made of glass. The insulating substrate 102 can also be a substrate used in large-scale integrated circuits, and multiple back-gate tunneling transistors 100 can be integrated on the same insulating substrate 102 according to a predetermined pattern or design.

[0097] The insulating layer 106 has an atomically smooth surface, and the material of the insulating layer 106 is boron nitride or the like. The thickness of the insulating layer 106 is 5 nanometers to 100 micrometers. In this embodiment, the material of the insulating layer 106 is hexagonal boron nitride, and the insulating layer 106 formed by hexagonal boron nitride has an atomically smooth surface.

[0098] The source electrode 108 and drain electrode 109 should be made of materials with good conductivity. Specifically, the materials of the source electrode 108 and drain electrode 109 can be metals, alloys, indium tin oxide (ITO), antimony tin oxide (ATO), conductive silver paste, conductive polymers, and metallic carbon nanotube films, etc. The thickness of the source electrode 108 and drain electrode 109 is 0.5 nanometers to 100 micrometers. In this embodiment, the source electrode 108 is an Au / Ti (gold / titanium, 50nm / 5nm thickness) electrode, which is formed by stacking a 5nm thick gold layer and a 5nm thick titanium layer. The 5nm thick Ti layer is in direct contact with the film structure 14, and the 50nm thick Au layer is disposed on the surface of the Ti layer away from the film structure 14. The drain electrode 109 is made of palladium (Pd) with a thickness of 50nm.

[0099] The gate 104 is made of a material with good conductivity. Specifically, the gate 104 can be made of conductive materials such as metals, alloys, ITO, ATO, conductive silver paste, conductive polymers, and carbon nanotube films. The metal or alloy material can be aluminum, copper, tungsten, molybdenum, gold, or alloys thereof. Specifically, the thickness of the gate 104 is 0.5 nanometers to 100 micrometers. In this embodiment, the gate 104 is highly doped silicon.

[0100] The present invention will be further illustrated by a specific embodiment below, but it should not be construed as a limitation of the present invention.

[0101] A highly doped silicon wafer (the silicon is highly doped and conductive, serving as gate 104) has a 300 nm thick oxide layer (the oxide layer is made of SiO2) on its surface. A hexagonal boron nitride (hBN) sheet (serving as insulating layer 106) is transferred onto the oxide layer using a transparent tape method. The hBN sheet is in direct contact with the oxide layer, which is located between the highly doped silicon wafer and the hBN sheet. Because the hBN sheet has an atomically flat surface without dangling bonds, it can shield against charge doping from the SiO2 surface. The inner shell of a suspended semiconducting carbon nanotube is pulled out, and then the semiconducting carbon nanotube is placed onto the hBN sheet using two tungsten tips. Only semiconducting carbon nanotubes are selected by electrical measurements. Since the inner shell of the semiconducting carbon nanotube is pulled out, the semiconducting carbon nanotube is either a single-walled carbon nanotube or a double-walled carbon nanotube. Under an optical microscope equipped with a micromanipulator, a MoS2 film is stacked on the semiconducting carbon nanotube, with the MoS2 film covering only a portion of the semiconducting carbon nanotube. Using standard processes including electron beam lithography (EBL), electron beam evaporation, and lift-off, Pd (palladium, 50 nm thick) and Au / Ti (gold / titanium, 50 nm / 5 nm) electrodes are used to connect the semiconducting carbon nanotube and the MoS2 film, respectively. Specifically, the Pd electrode is electrically connected to the semiconducting carbon nanotube, serving as the drain 109. The Au / Ti electrode is electrically connected to the MoS2 film, serving as the source 108. The semiconducting carbon nanotube serves as the channel layer. Thus, the back-gate tunneling transistor 100 is fabricated. Figure 12 As shown. Figure 12 The diagram shows the structure of the back-gate tunneling transistor 100 and the external measurement circuit diagram. The main body is a hybrid-dimensional heterojunction constructed from a semiconductor carbon nanotube and molybdenum disulfide. Palladium is used as the contact electrode of the semiconductor carbon nanotube, and titanium (5nm / 50nm) is used as the contact electrode of the molybdenum disulfide, so as to achieve good p-type ohmic contact and n-type ohmic contact respectively. Figure 12 In this design, the two electrodes in direct contact with molybdenum disulfide are titanium electrodes, while the three electrodes in direct contact with the semiconductor carbon nanotubes are palladium electrodes. This is understandable. Figure 12 In this test, only one titanium electrode can be in direct contact or electrically connected to molybdenum disulfide, and only one palladium electrode can be in direct contact or electrically connected to the semiconductor carbon nanotube. In the test, the heavily doped silicon substrate served as the gate electrode (104), the semiconductor carbon nanotube as the drain electrode (109), and the molybdenum disulfide as the source electrode (108).

[0102] The working principle of the back-gate tunneling transistor 100 is as follows: a MoS2 film covers and directly contacts a portion of the semiconducting carbon nanotube, which is transformed from p-type to n-type, so that one part of the semiconducting carbon nanotube is p-type and the other part is n-type. Therefore, the semiconducting carbon nanotube forms a pn junction. Under a specific gate voltage, the charge carriers can tunnel from the valence band of the p-type carbon nanotube to the conduction band of the n-type carbon nanotube. That is, the charge carriers are transported from the drain 109 to the source 108 through interband tunneling. The gate 104 controls the tunneling current by controlling the number of charge carriers in the carbon nanotube and MoS2, thereby realizing the switching of the transistor.

[0103] Figures 13 to 29 Yes Figure 12 Various performance characteristics of the back-gate tunneling transistor 100 were characterized. Figures 13 to 29 In this context, "CNT" represents semiconducting carbon nanotubes, "CNT with MoS2" represents a semiconducting carbon nanotube whose middle portion is covered by a MoS2 film (i.e., the contact portion), "Before contact" represents the period before the semiconducting carbon nanotubes and the MoS2 film come into contact, "After contact" represents the period after the semiconducting carbon nanotubes and the MoS2 film come into contact, "overlapped region" represents the overlapping region of the MoS2 film and the semiconducting carbon nanotubes (i.e., the contact portion), "BTBT region" represents the interband tunneling region where the interband tunneling mechanism dominates the transport of charge carriers within the corresponding gate voltage range, "Diffusion region" represents the region where the thermal diffusion mechanism dominates the transport and diffusion of charge carriers within the corresponding gate voltage range, and "BTBT current" represents the interband tunneling current.

[0104] Figure 13 The current scan graph of the back-gate tunneling transistor 100 is presented in logarithmic form, with the horizontal axis representing the gate voltage (gate 104 voltage) and the vertical axis representing the source-drain bias voltage. The two dashed lines delineate the operating modes of the back-gate tunneling transistor 100 under different gate voltages, from right to left: the nn junction region, the pn junction region, and the BTBT region. Figure 14 The curve shows the transfer characteristic of the back-gate tunneling transistor 100.

[0105] Figure 15 The typical output characteristic curve of the back-gate tunneling transistor 100 in BTBT operating mode is given by... Figure 15 It can be seen that the reverse current is greater than the forward current. Figure 16 The output characteristic curves of the back-gate tunneling transistor 100 in pn junction operating mode are shown. Figure 16 It exhibits obvious positive rectification characteristics. Figure 17The curve shows the typical output characteristic of the back-gate tunneling transistor 100 in nn-junction operating mode. Figure 17 It exhibits positive and negative symmetric output characteristics. The pn junction operating mode and the nn junction operating mode refer to different operating modes under gate voltage adjustment. The gate voltage range corresponding to the nn junction operating mode is approximately +35 to +45V, the gate voltage range corresponding to the pn junction operating mode is approximately +20V to +35V, and the gate voltage range corresponding to the BTBT operating mode is approximately -20V to +20V.

[0106] Figure 18 The diagram compares the transfer characteristic curves of a back-gate tunneling transistor 100 with a MoS2 film covering a single semiconducting carbon nanotube and a single carbon nanotube transistor fabricated on the same semiconducting carbon nanotube. The only difference between the single carbon nanotube transistor and the back-gate tunneling transistor 100 is that the single carbon nanotube transistor does not contain the MoS2 film, meaning the semiconducting carbon nanotube is not covered by MoS2; while the back-gate tunneling transistor 100 contains the MoS2 film, meaning a portion of the semiconducting carbon nanotube is covered by MoS2. Figure 18 In the middle, by Figure 18 As can be seen, in addition to the turn-off point shared with the individual carbon nanotube transistor at ~+35V, the transfer characteristic curve of the back-gate tunneling transistor 100 with MoS2 covering the semiconducting carbon nanotubes has an additional turn-off point near -5V. This proves that the doping levels of the MoS2-covered semiconducting carbon nanotubes (i.e., the contact portion) and the uncovered semiconducting carbon nanotubes (i.e., the exposed portion) are different. Before the single carbon nanotube 12 comes into contact with the MoS2 film, the single carbon nanotube 12 is a one-dimensional p-type channel, and the MoS2 film is a two-dimensional n-type channel. The Fermi level of the MoS2 film is higher than that of the single carbon nanotube 12 without contact with the MoS2 film. After the single carbon nanotube 12 comes into contact with the MoS2 film, electrons can spontaneously transfer from the MoS2 film to the single carbon nanotube 12 until the Fermi level of the single carbon nanotube 12 is aligned with or equal to that of the MoS2 film. Because electrons spontaneously transfer from the MoS2 film to the semiconducting carbon nanotubes covered by the MoS2 film (i.e., the contact portion), the semiconducting carbon nanotubes covered by the MoS2 film (i.e., the contact portion) change from p-type to n-type, while the semiconducting carbon nanotubes not covered by the MoS2 film (i.e., the exposed portion) remain p-type.

[0107] Figure 19 The photocurrent diagram of the back-gate tunneling transistor 100 is shown. Figure 19This can be reflected in the overlapping region of the MoS2 film and the semiconducting carbon nanotubes (i.e., the contact area), where the direction of the built-in electric field is from MoS2 to the semiconducting carbon nanotubes, proving the spontaneous transfer of electrons from MoS2 to the semiconducting carbon nanotubes.

[0108] Figure 20 This is the energy band diagram of the back-gate tunneling transistor 100 before the semiconducting carbon nanotubes and MoS2 film come into contact. Figure 21 This is an energy band diagram of the back-gate tunneling transistor 100 after the contact between the semiconducting carbon nanotubes and the MoS2 film. Figure 21 It can be seen that in the overlapping region of the MoS2 film and the semiconducting carbon nanotubes (i.e., the contact portion), the semiconducting carbon nanotubes change from p-type to n-type.

[0109] Figure 22 The curves show the transfer characteristics of the back-gate tunneling transistor 100 at different temperatures. Figure 23 From Figure 22 The subthreshold swing extracted in the diffusion region and BTBT region. Figure 23 As can be seen, in the diffusion region, the subthreshold swing decreases with decreasing temperature; while in the BTBT region, the subthreshold swing does not change with decreasing temperature. This proves that the back-gate tunneling transistor 100 does indeed operate under the inter-band tunneling mechanism in the BTBT region.

[0110] Figure 24 Typical output curves of the CNT-MoS2 heterostructure in the back-gate tunneling transistor 100 at different gate voltages in BTBT operating mode, plotted on a semi-logarithmic scale. Figure 25 This is the energy band diagram of a reverse rectifier diode under reverse bias. Figure 26 This is the energy band diagram of a Zener diode under reverse bias. Both the reverse rectifier diode and the Zener diode operate on the interband tunneling (BTBT) mechanism. The difference is that the reverse rectifier diode will generate reverse current under small reverse voltages, while the Zener diode will only activate reverse current when the reverse voltage reaches a specific value. Figure 27 The output curve is the temperature-dependent curve of the BTBT state when Vg = 20V. Figure 28 The inverse slope of the inter-band tunneling current (BTBT current) and forward bias current with respect to temperature when Vg = 20V. Figure 29 The source 108 and drain 109 current I at a temperature of 130K ds Image, by Figure 29 It can be seen that the acromion is clearly separated from the main peak. Figures 24 to 29 All of these analyses focus on the output characteristics of the BTBT region.

[0111] The fourth embodiment of the present invention further provides a comparative experiment between a metallic carbon nanotube field-effect transistor with an intermediate MoS2 film and a simple metallic carbon nanotube field-effect transistor to verify that the MoS2 film also performs n-type doping on the metallic carbon nanotubes. The only difference between the metallic carbon nanotube field-effect transistor with an intermediate MoS2 film and the back-gate tunneling transistor 100 is that the metallic carbon nanotube field-effect transistor with an intermediate MoS2 film uses metallic carbon nanotubes, while the back-gate tunneling transistor 100 uses semiconducting carbon nanotubes. The only difference between the simple metallic carbon nanotube field-effect transistor and the metallic carbon nanotube field-effect transistor with an intermediate MoS2 film is that the simple metallic carbon nanotube field-effect transistor does not contain the MoS2 film, that is, the metallic carbon nanotubes are not covered by the MoS2 film; the metallic carbon nanotube field-effect transistor with an intermediate MoS2 film contains the MoS2 film, that is, a portion of the metallic carbon nanotubes is covered by the MoS2 film.

[0112] Figure 30 The figures show the transfer characteristic curves of a simple metallic carbon nanotube field-effect transistor and a metallic carbon nanotube field-effect transistor covered with a MoS2 film. Figure 30 In this context, "mCNT" represents metallic carbon nanotubes. (The last part, "from," appears to be a fragment and doesn't translate directly.) Figure 30 It can be seen that for metallic carbon nanotubes coated with a MoS2 film, due to the electron doping of the MoS2 film on the coated metallic carbon nanotubes (i.e., the portion of the metallic carbon nanotube covered by the MoS2 film), an additional Dirac point appears in the transfer characteristic curve, as shown by the arrow. This proves that the MoS2 film also performs n-type doping on the metallic carbon nanotubes; that is, the portion of the metallic carbon nanotube covered by the MoS2 film changes from p-type to n-type, while the portion of the metallic carbon nanotube not covered by the MoS2 film remains p-type.

[0113] Please see Figure 31 The fifth embodiment of the present invention provides a top-gate tunneling transistor 200, which includes a single carbon nanotube 12, a film structure 14, a source 108, a drain 109, an insulating layer 106, and a gate 104. The top-gate tunneling transistor 200 can be formed on the surface of an insulating substrate 102. The single carbon nanotube 12 is a semiconducting carbon nanotube.

[0114] The single carbon nanotube 12 is disposed on the surface of the insulating substrate 102. The film structure 14 covers a portion of the single carbon nanotube 12 and is in direct contact with the outer surface of that portion. Since the single carbon nanotube 12 is one-dimensional and the film structure 14 is two-dimensional, a portion of the film structure 14 is in direct contact with a portion of the single carbon nanotube 12, and another portion of the film structure 14 is in direct contact with the insulating substrate 102. The drain 109 is electrically connected to the single carbon nanotube 12, and the source 108 is electrically connected to the film structure 14. The insulating layer 106 covers the source 108, the film structure 14, the single carbon nanotube 12, and the drain 109. The gate 104 is disposed on the surface of the insulating layer 106 away from the insulating substrate 102. That is, the insulating layer 106 makes the source 108, the film structure 14, the single carbon nanotube 12, and the drain 109 electrically insulated from the gate 104.

[0115] It is understood that, depending on the specific formation process, the insulating layer 106 does not need to completely cover the source electrode 108, the film structure 14, the single carbon nanotube 12 and the drain electrode 109, as long as it can ensure that the source electrode 108, the film structure 14, the single carbon nanotube 12, the drain electrode 109 are insulated from the gate electrode 104.

[0116] The top-gate tunneling transistor 200 provided in the fifth embodiment is similar to the back-gate tunneling transistor 100 provided in the fourth embodiment, except that the former is a top-gate type and the latter is a back-gate type. The structure, materials, and dimensions of the single carbon nanotube 12, the film structure 14, the source 108, the drain 109, the insulating layer 106, and the gate 104 in the fifth embodiment are the same as those in the fourth embodiment, and will not be described again here.

[0117] The back-gate tunneling transistor 100 provided in the fourth embodiment and the top-gate tunneling transistor 200 provided in the fifth embodiment have the following advantages: First, the single semiconductor carbon nanotube contains both p-type and n-type electrons, allowing electrons to tunnel from the p-type to the n-type, achieving band-to-band tunneling (BTBT); Second, the combination of the one-dimensional single semiconductor carbon nanotube and the two-dimensional MoS2 film (or WS2 film) provides excellent gate 104 controllability; Third, the unique single semiconductor carbon nanotube and the two-dimensional MoS2 film (or WS2 film) have a strong coupling ideal interface, which can improve the conduction current and reduce the subthreshold swing; Fourth, the insulating layer 106 has an atomically flat surface. Because the surface of the insulating layer 106 is atomically flat and has no dangling bonds, the insulating layer 106 can shield the charge doping from the surface of the gate 104.

[0118] Please see Figure 32The sixth embodiment of the present invention provides a method for p-type doping of carbon nanotubes, which includes the following steps:

[0119] S61 provides a single carbon nanotube 12;

[0120] S62, provides a layered structure 16, which is a tungsten diselenide (WSe2) film or a black phosphorus (BP) film; and

[0121] S63, the layered structure 16 is brought into direct contact with at least a portion of the single carbon nanotube 12.

[0122] In step S62, both the tungsten diselenide (WSe2) film and the black phosphorus (BP) film are two-dimensional film structures 14. The material of the WSe2 film is WSe2, and the material of the black phosphorus film is black phosphorus.

[0123] In step S63, the single carbon nanotube 12 can be completely covered by the layered structure 16, or it can be partially covered by the layered structure 16. That is, the layered structure 16 can cover and directly contact a portion of the single carbon nanotube 12, while another portion of the single carbon nanotube 12 is exposed. The layered structure 16 can also cover and directly contact the entire single carbon nanotube 12. All carbon nanotube portions covered by the layered structure 16 are in direct contact with the layered structure 16. That is, the layered structure 16 can directly contact a portion of the single carbon nanotube 12, or it can directly contact the entire single carbon nanotube 12. Figure 33 As shown, the layered structure 16 covers and directly contacts a portion of the individual carbon nanotubes 12. Figure 34 As shown, the layered structure 16 covers and directly contacts the entire upper surface of the single carbon nanotube 12.

[0124] The portion of the single carbon nanotube 12 that is in direct contact with the layered structure 16 is defined as the contact portion, and the portion of the single carbon nanotube 12 that is not in direct contact with the layered structure 16 is defined as the exposed portion. That is, the single carbon nanotube 12 consists of a contact portion and an exposed portion.

[0125] Carbon nanotubes are inherently p-type; however, in practical applications, they still require p-doping. The layered structure 16 directly contacts the contact portion, and WSe2 or black phosphorus contributes holes to this contact portion. That is, holes enter the contact portion from WSe2 or black phosphorus, thus p-doping the contact portion. At this time, the exposed portion of the single carbon nanotube 12 remains p-type. In other words, the entire single carbon nanotube 12 is p-type.

[0126] The p-type doping method for carbon nanotubes provided in the sixth embodiment is similar to the n-type doping method for carbon nanotubes provided in the first embodiment. The difference lies in the following: In the first embodiment, a film structure 14 is used to cover part or all of a single carbon nanotube 12. The material of the film structure 14 is molybdenum disulfide or tungsten disulfide, thereby causing the carbon nanotube portion covered by the film structure 14 to be n-type doped, transforming it from p-type to n-type. That is, part of the single carbon nanotube 12 is p-type and part is n-type. In the sixth embodiment, a layered structure 16 is used to cover part or all of a single carbon nanotube 12. The material of the layered structure 16 is tungsten diselenide or black phosphorus, thereby causing the carbon nanotube portion covered by the layered structure 16 to be p-type doped, and the entire single carbon nanotube 12 is p-type. The type and size of the single carbon nanotube 12 and the size of the layered structure 16 in the sixth embodiment are the same as those in the first embodiment, and will not be repeated here.

[0127] The sixth embodiment of the present invention further provides a comparative experiment between a carbon nanotube field-effect transistor covered with a WSe2 film and a simple carbon nanotube field-effect transistor to verify that the WSe2 film performs p-type doping on the carbon nanotubes. The only difference between the simple carbon nanotube field-effect transistor and the carbon nanotube field-effect transistor covered with a WSe2 film is that the simple carbon nanotube field-effect transistor does not contain the WSe2 film, that is, the carbon nanotubes are not covered by the WSe2 film; while the carbon nanotube field-effect transistor covered with a WSe2 film contains the WSe2 film, that is, a portion of the carbon nanotubes is covered by the WSe2 film.

[0128] Figure 35 The figures show the transfer characteristic curves of a carbon nanotube field-effect transistor with a WSe2 film covering the middle section and a pure carbon nanotube field-effect transistor. Figure 35It can be seen that, in addition to the turn-off point shared with standalone carbon nanotube field-effect transistors at ~-18V, the transfer characteristic curve of the back-gate tunneling transistor with WSe2 covering the middle of the semiconducting carbon nanotube has an additional turn-off point near +5V. This proves that the doping levels of the WSe2-covered semiconducting carbon nanotube (i.e., the contact portion) and the uncovered semiconducting carbon nanotube (i.e., the exposed portion) are different. Before the two come into contact, a single carbon nanotube is a one-dimensional bipolar channel dominated by p-type, while the WSe2 film is a two-dimensional p-type channel. After the two come into contact, holes spontaneously transfer from the WSe2 film to the WSe2-covered semiconducting carbon nanotubes. Therefore, when the carbon nanotubes not covered by WSe2 change from p-type to n-type under gate voltage adjustment, the semiconducting carbon nanotubes covered by WSe2 remain p-type. Only when the holes in WSe2 are depleted does the portion of the carbon nanotube covered by WSe2 change from p-type to n-type, forming the second turn-off point. This proves that the portion of the carbon nanotube covered by the WSe2 film is p-type doped, while the portion not covered by the WSe2 film is not p-type doped.

[0129] Please see Figure 36 The seventh embodiment of the present invention provides a method for p-type doping of carbon nanotubes, which includes the following steps:

[0130] S71 provides multiple spaced single carbon nanotubes 12;

[0131] S72, provides a layered structure 16, which is a tungsten diselenide (WSe2) film or a black phosphorus (BP) film; and

[0132] S73, the layered structure 16 simultaneously covers the plurality of individual carbon nanotubes 12, and at least a portion of each individual carbon nanotube 12 directly contacts the layered structure 16.

[0133] The method for p-type doping of carbon nanotubes provided in the seventh embodiment is similar to the method for p-type doping of carbon nanotubes provided in the sixth embodiment, except that: in the sixth embodiment, a tungsten diselenide (WSe2) film or a black phosphorus (BP) film covers at least a portion of a single carbon nanotube 12; in the seventh embodiment, a tungsten diselenide (WSe2) film or a black phosphorus (BP) film simultaneously covers at least a portion of multiple spaced single carbon nanotubes 12.

[0134] In step S71, the extension directions of the multiple spaced individual carbon nanotubes 12 are parallel to each other.

[0135] In step S73, the tungsten diselenide (WSe2) film or black phosphorus (BP) film can simultaneously cover a portion of multiple individual carbon nanotubes 12, thereby enabling a portion of each individual carbon nanotube 12 to be p-type doped. Alternatively, the tungsten diselenide (WSe2) film or black phosphorus (BP) film can simultaneously cover the entirety of multiple individual carbon nanotubes 12, thereby enabling the entirety of each individual carbon nanotube 12 to be p-type doped.

[0136] The p-type doping method for carbon nanotubes provided in the sixth and seventh embodiments has the following advantages: First, the tungsten diselenide (WSe2) film or black phosphorus (BP) film directly contacts part or all of the single carbon nanotube 12, which can achieve p-type doping of the single carbon nanotube 12; Second, multiple single carbon nanotubes 12 can be p-doped simultaneously; Third, the method is simple and the p-type doping effect is good.

[0137] Furthermore, those skilled in the art may make other changes within the spirit of this invention. Of course, all such changes made in accordance with the spirit of this invention should be included within the scope of protection claimed by this invention.

Claims

1. A tunneling transistor comprising a gate, an insulating layer, a source, and a drain, wherein the insulating layer is disposed on the surface of the gate; characterized in that, The tunneling transistor further includes a single carbon nanotube and a film structure. The single carbon nanotube is disposed on the surface of the insulating layer away from the gate, and the single carbon nanotube is a semiconducting carbon nanotube. The film structure directly contacts a portion of the single carbon nanotube, and the film structure is a molybdenum disulfide film or a tungsten disulfide film. The material of the molybdenum disulfide film is molybdenum disulfide, and the material of the tungsten disulfide film is tungsten disulfide. The film structure covers and directly contacts a portion of the single carbon nanotube, thereby making the portion of the single carbon nanotube directly contacting the film structure n-type. The source is electrically connected to the film structure, and the drain is electrically connected to the single carbon nanotube.

2. The tunneling transistor as claimed in claim 1, characterized in that, The insulating layer has an atomically flat surface.

3. The tunneling transistor as claimed in claim 1, characterized in that, The insulating layer is made of hexagonal boron nitride.

4. The tunneling transistor as claimed in claim 1, characterized in that, The gate is a doped silicon wafer, and the surface of the doped silicon wafer has an oxide layer.

5. The tunneling transistor as claimed in claim 1, characterized in that, It further includes an insulating substrate, wherein the single carbon nanotube is disposed on the surface of the insulating substrate.

6. The tunneling transistor as claimed in claim 1, characterized in that, The single carbon nanotube is either a single-walled carbon nanotube or a double-walled carbon nanotube.

7. The tunneling transistor as claimed in claim 1, characterized in that, One part of the single carbon nanotube is p-type and the other part is n-type.

8. The tunneling transistor as claimed in claim 7, characterized in that, Electrons tunnel from the p-type to the n-type, thus achieving interband tunneling.

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