α-GeTe two-dimensional material and its PVD preparation method and application

Abstract

The present invention belongs to the field of two-dimensional material preparation, and specifically discloses a PVD preparation method for α-GeTe two-dimensional material, in which GeTe raw material is heated and volatilized at 600-700°C, and the volatilized raw material is physically vapor deposited on the surface of a substrate without dangling bonds at a temperature of 340-380°C in a hydrogen-containing carrier gas to obtain an α-GeTe two-dimensional material; the hydrogen-containing carrier gas is a mixture of hydrogen and a protective atmosphere, wherein the flow rate of hydrogen is 1-10 sccm and the flow rate of the protective atmosphere is 70-90 sccm. The present invention also discloses the materials and applications obtained by the preparation method. The technical solution of the present invention can extend atomically thin α-GeTe 2D metal nanosheets in a two-dimensional manner; for the first time, the controllable preparation of atomically thick α-GeTe nanosheets is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of two-dimensional material preparation, and specifically relates to the field of preparation of α-GeTe two-dimensional materials. Technical Background

[0002] Two-dimensional (2D) materials have become a new material platform for basic research and potential applications of the next generation of atomically thin devices due to their wide range of physical and chemical properties. They are currently widely used in the field of electronic devices. 1-3 , optoelectronics field 4,5 , valleytronics, and spintronics 6,7 ,sensor 8,9 and energy storage 10,11 Although most efforts have focused on graphene and 2D semiconductors, 2D metal materials (e.g., TaS2 12 , TaSe2 13 , NbSe2 14 , T d -MoTe2 15 , and VS2 16 ) has attracted considerable attention due to its special physical properties. It is reported that NbSe2 exhibits thickness-dependent superconducting properties, with the transition temperature increasing from 1.0K to 4.56K as the number of layers increases from a single layer to 10 layers. 17 VS2 nanosheets have excellent electrical conductivity (3×105S m -1 ) and apply it to the next generation of electronics 18,19 . Two-dimensional PtTe2 single crystals have strong thickness-tunable electrical properties 20 , and NiTe2 has a similar conductivity change trend 21 As a new member of the 2D materials family, MTMDs possess rich physical properties and exciting potential for future electronic, spintronic, and catalytic applications.

[0003] In addition to the limited size and scalability of mechanically exfoliated flakes, chemical vapor deposition (CVD) is characterized by good controllability and ease of mass production. Currently, CVD has been widely used in two-dimensional TMDC materials. In particular, various 2D-TMD semiconductors (e.g., MoSe2 22 ,WSe2 23 ,) and its heterostructure 24 In addition, CVD preparation of metallic two-dimensional materials has also been widely reported. As the thickness decreases, PtSe2 and TaTe2 undergo a metal-to-semiconductor transition. 25,26. The emergence of two-dimensional metallic materials has solved the contact problem of two-dimensional materials in the construction of electronic and optoelectronic devices. Two-dimensional metallic materials can form ideal vdW interfaces and can strongly suppress the metal-induced gap states formed in semiconductors. It is an important step for the practical application of two-dimensional semiconductor materials in electronic and optoelectronic devices. However, the resulting thickness of 2D-MTMD is usually in the range of a few nanometers to tens of nanometers. In particular, the growth of monolayer MTMD, which is crucial for the basic research and potential technological applications of this type of new materials confined in 2D, remains a major challenge.

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[0033] In order to fill the gap in the preparation of α-GeTe two-dimensional materials, the first purpose of the present invention is to provide a PVD synthesis method for α-GeTe two-dimensional materials, aiming to successfully prepare α-pure phase and two-dimensional non-layered α-GeTe two-dimensional materials with ultra-thin structure.

[0034] The second purpose of the present invention is to provide an α-GeTe two-dimensional material prepared by the preparation method and its application in micro-nanoelectronic devices.

[0035] The third object of the present invention is to provide a micro-nanoelectronic device comprising the α-GeTe two-dimensional material.

[0036] The industry has provided some reports on the CVD preparation of two-dimensional materials of metal tellurides such as V, Nb, and Ta, but there are no reports on the preparation of α-GeTe two-dimensional materials. In addition, it is well known in the industry that for materials of different elements, their properties are different, and technical solutions are difficult to simply transfer, and it is also difficult to predict the effect of the transfer. For example, for the preparation of GeTe two-dimensional materials, the activity of the materials is low and it is difficult to successfully prepare them. In addition, GeTe exists in multiple phases such as α, β, and γ. The phase purity, thickness, morphology and performance of the products prepared by existing preparation methods are also not ideal. In order to fill the gap in the preparation of α-GeTe two-dimensional materials and improve the preparation effect, the present invention provides the following solutions:

[0037] A PVD preparation method for α-GeTe two-dimensional materials comprises volatilizing GeTe raw materials at 600-700°C, and physically vapor depositing the volatilized raw materials on a substrate surface without dangling bonds at a deposition temperature of 340-380°C in a hydrogen-containing carrier gas to prepare the α-GeTe two-dimensional material.

[0038] The hydrogen-containing carrier gas is a mixture of hydrogen and a protective atmosphere, wherein the flow rate of the hydrogen is 1 to 10 sccm, and the flow rate of the protective atmosphere is 70 to 90 sccm.

[0039] This invention proposes for the first time the use of PVD to synthesize α-GeTe two-dimensional materials. Research has found that PVD synthesis of α-GeTe two-dimensional materials is prone to problems such as vertical growth rates exceeding lateral growth rates, difficulty in lateral deposition, and unsatisfactory crystallinity, phase purity, and poor morphology uniformity. To address these challenges faced by the α-GeTe PVD preparation process, the present invention has discovered that the innovative use of hydrogen-assisted PVD for the preparation of α-GeTe two-dimensional materials, combined with the lack of an overhanging substrate, combined with the combined control of deposition temperature and carrier gas flow, can unexpectedly effectively induce lateral growth of α-GeTe and inhibit vertical growth. Furthermore, it can effectively induce the α phase, resulting in the preparation of ultra-thin single-crystal α-GeTe two-dimensional materials with excellent crystallinity, phase purity, and uniform morphology.

[0040] In the present invention, the use of a PVD preparation method without a suspended substrate and assisted by a hydrogen atmosphere, and the joint control of the atmosphere and temperature during the PVD deposition process are the key to synergistically solving the problems of GeTe two-dimensional materials, such as difficulty in preparation, multiple impurities, easy vertical growth, and poor morphology uniformity.

[0041] In the present invention, the substrate without dangling bonds is mica or a two-dimensional material substrate, preferably a two-dimensional material substrate. The present invention has found that the use of a two-dimensional material substrate can further cooperate with the hydrogen-assisted PVD process, achieving superior synergistic performance in the successful preparation of α-GeTe two-dimensional materials and improving their physical phase, morphology, and thickness.

[0042] The two-dimensional material substrate is a substrate on which MX2 two-dimensional material is deposited.

[0043] Preferably, the M is a transition metal element, more preferably at least one of Mo and W;

[0044] Preferably, X is at least one of S and Se;

[0045] Preferably, the substrate without dangling bonds has a flat surface.

[0046] Preferably, in the two-dimensional material substrate, the planar size of the two-dimensional material is greater than or equal to 50 um; preferably greater than or equal to 200 um.

[0047] In the present invention, the purity of the GeTe raw material is greater than or equal to 99%, and more preferably greater than or equal to 99.9%.

[0048] In the present invention, the volatilization temperature of the GeTe raw material is 620-675°C, more preferably 620-630°C.

[0049] In the present invention, in the hydrogen-containing carrier gas, the protective atmosphere is at least one of nitrogen and an inert gas.

[0050] In the present invention, hydrogen-assisted PVD is used to effectively improve the lateral growth of α-GeTe, help induce the α phase, regulate the morphology of the material, and facilitate the preparation of materials with high phase purity, uniform morphology, and atomic-level thickness.

[0051] The present invention has found that under the hydrogen-assisted PVD preparation process, further combined with the joint control of the atmosphere and PVD temperature can further synergize and further improve the α phase, high crystallinity, uniform morphology and atomic-level thickness of the α-GeTe two-dimensional material.

[0052] In the present invention, the flow rate of hydrogen in the hydrogen-containing carrier gas is 2 to 8 sccm, preferably 4 to 8 sccm, and the flow rate of the protective atmosphere is 75 to 85 sccm.

[0053] In the present invention, the temperature of physical vapor deposition is 340 to 360°C, more preferably 340 to 350°C.

[0054] The study found that under optimal carrier gas and PVD deposition temperature, the purity of the α phase can be further synergistically improved, which is conducive to obtaining materials with atomic-level thickness.

[0055] In the present invention, the physical vapor deposition time is 5 to 15 minutes, preferably 8 to 12 minutes.

[0056] The present invention also provides an α-GeTe two-dimensional material prepared by the preparation method.

[0057] The present invention also provides an application of the α-GeTe two-dimensional material prepared by the preparation method, which is used to prepare micro-nanoelectronic devices;

[0058] The micro-nano device electrical device is, for example, a field effect transistor.

[0059] In the present invention, the α-GeTe two-dimensional material can be prepared into the desired micro-nanoelectronic devices based on existing methods. For example, the steps for preparing a field-effect transistor using the prepared α-GeTe two-dimensional nanosheets are as follows:

[0060] The sample was marked by electron beam exposure on the surface of α-GeTe two-dimensional nanosheets without dangling bonds, and then metal was deposited on the surface to obtain a field effect transistor.

[0061] Preferably, the metal is deposited on the surface of the α-GeTe nanosheets by a vacuum coating machine;

[0062] Preferably, the metals are Cr and Au.

[0063] The present invention also provides a field effect transistor device, comprising the α-GeTe two-dimensional material prepared by the preparation method, or prepared from the α-GeTe two-dimensional material.

[0064] Beneficial effects

[0065] 1. The present invention provides an α-GeTe two-dimensional material.

[0066] 2. This invention innovatively employs hydrogen-assisted PVD, coupled with the combined control of the absence of an overhanging substrate, deposition temperature, and carrier gas flow rate, to unexpectedly effectively induce lateral growth of α-GeTe and inhibit vertical growth. Furthermore, it effectively induces the α-phase, thereby producing ultrathin α-GeTe two-dimensional materials with excellent crystallinity, phase purity, and uniform morphology. The invention achieves the growth of ultrathin, especially atomically thin, MTMDs, which is crucial for fundamental research and potential technological applications of these new 2D-confined materials. The invention's preparation process eliminates complex steps and the use of expensive raw materials, resulting in simple equipment, easy operation, and excellent reproducibility.

[0067] The germanium telluride nanosheets prepared by the present invention can have a thickness of atomic level and a size of 2 to 30 μm, have regular hexagonal or triangular morphology, good crystallinity and high quality.

[0068] 3. The α-GeTe two-dimensional material produced by the present invention has excellent semiconductor properties. For example, the method can be used to prepare metal germanium telluride contact WSe2 field-effect transistors. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 Schematic diagram of the atmospheric pressure chemical vapor deposition apparatus for preparing germanium telluride nanosheets;

[0070] Figure 2 Schematic diagram of the optical structure of germanium telluride nanosheets prepared on a WSe2 substrate in Example 1-1;

[0071] Figure 3 This is the X-ray energy spectrum of the germanium telluride nanosheets prepared on the WSe2 substrate in Example 1-1;

[0072] Figure 4 This is a statistical graph of the thickness of germanium telluride nanosheets prepared on a WSe2 substrate in Example 1-1;

[0073] Figure 5 Schematic diagram of the optical structure of germanium telluride nanosheets prepared on a mica substrate in Example 1-2;

[0074] Figure 6 This is a statistical graph of the thickness of germanium telluride nanosheets prepared on a mica substrate in Example 1-2;

[0075] Figure 7 Schematic diagram of the optical product prepared in Comparative Example 1-1 on a SiO2 / Si substrate;

[0076] Figure 8 Statistical graph of thickness of the product prepared in Comparative Example 1-1 on a SiO2 / Si substrate;

[0077] Figure 9 Schematic diagram of the optical product prepared in Comparative Example 1-2 on a WSe2 substrate;

[0078] Figure 10 Thickness statistics of the products prepared in Comparative Examples 1-2 on a WSe2 substrate;

[0079] Figure 11 Schematic diagram of the optical structure of germanium telluride nanosheets prepared on a WSe2 substrate in Example 1-2;

[0080] Figure 12 Statistical graph of the thickness of germanium telluride nanosheets prepared on WSe2 substrates in Examples 1-2;

[0081] Figure 13 Schematic diagram of optical structure of germanium telluride nanosheets prepared on WS2 substrate in Examples 1-3;

[0082] Figure 14 Statistical graph of the thickness of germanium telluride nanosheets prepared on WSe2 substrates in Examples 1-3;

[0083] Figure 15 Optical images of germanium telluride nanosheets prepared on WSe2 substrates in Examples 1-4;

[0084] Figure 16 Statistical graph of the thickness of germanium telluride nanosheets prepared on WSe2 substrates in Examples 1-4;

[0085] Figure 17Optical images of germanium telluride nanosheets prepared on WSe2 substrates in Examples 1-5;

[0086] Figure 18 Statistical graph of the thickness of germanium telluride nanosheets prepared on WSe2 substrates in Examples 1-5;

[0087] Figure 19 Optical images of germanium telluride nanosheets prepared on WSe2 substrates in Examples 1-6;

[0088] Figure 20 Statistical graph of the thickness of germanium telluride nanosheets prepared on WSe2 substrates in Examples 1-6;

[0089] Figure 21 is an optical image of the product prepared in Comparative Examples 1-3 on a SiO2 / Si substrate;

[0090] Figure 22 Optical images of the products prepared in Comparative Examples 1-4 on SiO2 / Si substrates;

[0091] Figure 23 Schematic diagram of the optical structure of the GeTe device prepared on the WSe2 substrate in Example 2-1;

[0092] Figure 24 This is the output curve of the α-GeTe field effect transistor in Example 2-1;

[0093] Figure 25 This is the transfer curve of the α-GeTe field effect transistor of Example 2-1;

[0094] Figure 26 The relationship between conductivity and thickness of the α-GeTe field effect transistor in Example 2-1 is shown;

[0095] Figure 27 This is the breakdown curve of the α-GeTe field effect transistor of Example 2-1;

[0096] Figure 28 Schematic diagram of a WSe2 field-effect transistor using α-GeTe nanosheets as metal electrodes in Example 2-2;

[0097] Figure 29 This is an optical image of a WSe2 field-effect transistor with α-GeTe nanosheets as metal electrodes in Example 2-2;

[0098] Figure 30 This is the output curve of the WSe2 field effect transistor with α-GeTe nanosheets as metal electrodes in Example 2-2;

[0099] Figure 31This is the transfer curve of the WSe2 field effect transistor with α-GeTe nanosheets as the metal electrode in Example 2-2;

[0100] Figure 32 Schematic diagram of a WSe2 field effect transistor with comparative example 2-1Cr / Au as the metal electrode;

[0101] Figure 33 This is an optical schematic diagram of a WSe2 field-effect transistor with comparative example 2-1Cr / Au as the metal electrode;

[0102] Figure 34 The output curve of the WSe2 field effect transistor with Cr / Au as the metal electrode in comparative example 2-1;

[0103] Figure 35 The output curve of the WSe2 field effect transistor with Cr / Au as the metal electrode in comparative example 2-1; Specific implementation methods

[0104] The present invention is further described below through examples of implementation, but the content of the present invention is not limited to the following content.

[0105] In the following cases of the present invention, the two-dimensional material substrate without dangling bonds is taken as an example of a WSe2 nanosheet substrate, which can be obtained based on conventional means. For example, in this case, the preparation steps are as follows: first, 100 mg of tungsten selenide raw material is placed in the center of a tube furnace, purged with 1200 sccm Ar gas to remove oxygen, and then the Ar gas flow rate is changed to 80 sccm and blown from the downstream to the upstream of the heating zone (reverse airflow: 285 nm SiO2 / Si substrate to raw material), the heating program is set to 40 min, heated to 1180 ° C and kept at a constant temperature for two minutes, and the direction of the Ar gas is changed to grow from upstream to downstream for three minutes (forward airflow: raw material to 285 nm SiO2 / Si substrate), cooled naturally, and deposited on the 285 nm SiO2 / Si substrate to obtain WSe2 nanosheets. It should be noted that the substrate and preparation are only an enumeration of the implementation of the technical solution and do not constitute a necessary technical limitation of the method of the present invention.

[0106] In the following cases, the purity of the GeTe raw material is above 99.99%.

[0107] 1. Preparation of α-GeTe nanosheets on two-dimensional material substrates:

[0108] Example 1-1

[0109] The experimental setup of α-GeTe nanosheets is shown in the figure. Figure 1 shown. Figure 1The figure above shows the apparatus for preparing a WSe2 nanosheet substrate. This WSe2 nanosheet substrate (also referred to herein as a WSe2 two-dimensional material substrate, or WSe2 substrate) can be prepared using existing methods. A porcelain boat containing GeTe powder is placed in constant temperature zone 1 of a tube furnace. A 285nm SiO2 / Si substrate with WSe2 nanosheets, serving as the growth substrate for germanium telluride, is placed on another porcelain boat and placed in constant temperature zone 2 of the tube furnace to achieve the appropriate crystal growth temperature. Before heating, the air in the quartz tube is purged with a high flow rate (600 sccm) of argon. Under the reverse carrier gas flow (constant temperature zone 2 to constant temperature zone 1), the temperatures of constant temperature zone 1 and constant temperature zone 2 are increased to 625°C (volatization temperature) and 340°C (physical vapor deposition temperature), and then switched to a forward carrier gas (constant temperature zone 1 to constant temperature zone 2). Under the action of the carrier gas, the volatilized raw materials are physically vapor deposited on the surface of the WSe2 nanosheets. The carrier gas is Ar-H2, the argon flow rate is 80 sccm, the hydrogen flow rate is 7.8 sccm, and the physical vapor deposition time is 10 minutes.

[0110] Single crystal α-GeTe nanosheets will be generated on the WSe2 substrate. The optical photos of the prepared α-GeTe nanosheets are as follows: Figure 2 shown.

[0111] Figure 2 This is an optical schematic diagram of the α-GeTe nanosheets prepared in this case. 1 in the figure represents SiO2 / Si, 2 in the figure represents WSe2, and 2 in the figure represents the grown α-GeTe. Figure 3 The XRD diagram shows that α-GeTe has good crystallinity ( Figure 3 ), the thickness reaches the atomic level, distributed in the range of 1.2 to 5 nm, and the size is 2 to 30 μm. Figure 2 The scale bar in the figure is 5 μm. Figure 4 Thickness statistics chart.

[0112] Example 1-2

[0113] Compared with Example 1-1, the only difference is that mica is used as the PVD deposition substrate instead of the 285nm SiO2 / Si substrate on which the WSe2 nanosheets are grown. Other operations and parameters are the same as in Example 1.

[0114] Figure 5 This is an optical schematic diagram of α-GeTe nanosheets prepared on a mica substrate. The α-GeTe nanosheets obtained under this condition have good crystallinity and thin thickness, ranging from 40 to 160 nm, and a size of 2 to 30 μm. Figure 5 The scale bar in the figure is 10 μm. Figure 6 Thickness statistics chart.

[0115] Comparative Example 1-1

[0116] Compared with Example 1-1, the only difference is that SiO2 / Si (with a suspended substrate) is used as the PVD substrate instead of the 285nm SiO2 / Si on which the WSe2 nanosheets are grown. Other operations and parameters are the same as in Example 1. Figure 7 This is an optical schematic diagram of the product prepared on a SiO2 / Si substrate. 1 in the figure represents SiO2 / Si, and 2 in the figure represents α-GeTe. The α-GeTe nanosheets obtained under this condition have poor crystallinity, are thick, and are small in size. Figure 7 The scale bar in the figure is 10 μm. Figure 8 Thickness statistics chart.

[0117] Comparative Example 1-2

[0118] The only difference from Example 1-1 is that no hydrogen was added to the carrier gas. The carrier gas flow rates were: Ar flow rate of 80 sccm, H2 flow rate of 0 sccm. Other operations and parameters were the same as in Example 1.

[0119] Figure 9 This is an optical schematic diagram of the product prepared on a WSe2 substrate. The thickness of the nanosheets obtained under this condition ranges from 40 to 160 nm, and the size ranges from 2 to 30 μm. Figure 9 The scale bar in the figure is 10 μm. Figure 10 Thickness statistics chart.

[0120] Example 1-2

[0121] Compared with Example 1-1, the difference is that the GeTe volatilization temperature (constant temperature zone 1) is 650°C, the temperature of the WSe2 substrate (constant temperature zone 2) is 350°C, the Ar flow rate in the carrier gas is 80sccm, H27.8sccm, and the deposition time is 10min. Figure 11 This is an optical schematic diagram of α-GeTe nanosheets prepared on a WSe2 substrate. The α-GeTe nanosheets obtained under this condition have good crystallinity and are slightly thicker, reaching the atomic level, distributed in the range of 5 to 15 nm, and sized from 2 to 30 μm. Figure 11 The scale bar in the figure is 10 μm. Figure 12 Thickness statistics chart.

[0122] Examples 1-3

[0123] Compared with Example 1-1, the difference is that the volatilization temperature of GeTe is 675°C, the temperature of the WSe2 substrate (constant temperature zone 2) is 360°C, the Ar flow rate in the carrier gas is 80 sccm, H27.8 sccm, and the deposition time is 10 min. Figure 13This is an optical schematic diagram of α-GeTe nanosheets prepared on a WSe2 substrate. The α-GeTe nanosheets obtained under this condition have good crystallinity and are slightly thicker, reaching the atomic level, distributed in the range of ~30nm, and sized from 2 to 30μm. Figure 13 The scale bar in the figure is 10 μm. Figure 14 Thickness statistics chart.

[0124] Examples 1-4

[0125] Compared with Example 1-1, the only difference is that the H2 flow rate in the carrier gas is 2 sccm. Figure 15 This is an optical schematic diagram of α-GeTe nanosheets prepared on a WSe2 substrate. The α-GeTe nanosheets obtained under this condition have good crystallinity and are slightly thicker, reaching the atomic level, distributed in the range of 30 to 60 nm, and sized from 2 to 30 μm. Figure 15 The scale bar in the figure is 10 μm. Figure 16 Thickness statistics chart.

[0126] Examples 1-5

[0127] Compared with Example 1-1, the only difference is that the H2 flow rate in the carrier gas is 4 sccm. Figure 17 This is an optical schematic diagram of α-GeTe nanosheets prepared on a WSe2 substrate. The α-GeTe nanosheets obtained under this condition have good crystallinity and are slightly thicker, reaching the atomic level, distributed in the range of 1 to 5 nm, and sized from 2 to 30 μm. Figure 17 The scale bar in the figure is 10 μm. Figure 18 Thickness statistics chart.

[0128] Examples 1-6

[0129] Compared with Example 1-1, the only difference is that the H2 flow rate in the carrier gas is 8 sccm. Figure 19 This is an optical schematic diagram of α-GeTe nanosheets prepared on a WSe2 substrate. The α-GeTe nanosheets obtained under this condition have good crystallinity and are slightly thicker, reaching the atomic level, distributed in the range of 3 to 12 nm, and sized from 2 to 30 μm. Figure 19 The scale bar in the figure is 10 μm. Figure 20 Thickness statistics chart.

[0130] Comparative Examples 1-3

[0131] Compared with Example 1-1, the only difference is that the temperature of constant temperature zone 1 is 710° C., the flow rate of Ar in the carrier gas is 80 sccm, H20 sccm, and the deposition time is 10 min. Figure 21 Optical schematic diagram of the prepared product. The prepared material has no regularity and the preparation failed.

[0132] Comparative Examples 1-4:

[0133] Compared with Example 1-1, the only difference is that the CVD method is used for preparation, and the steps are:

[0134] A dual-temperature zone tubular furnace similar to that used in Example 1-1 was used, wherein a mixture of (50 mg) tellurium powder and (50 mg) germanium powder was placed in a porcelain boat 1, which was then placed in the upstream heating zone (constant temperature zone 1). The WSe2 two-dimensional material was deposited in the deposition zone (constant temperature zone 2), downstream of the carrier gas flow. Under a countercurrent flow (constant temperature zone 2 to constant temperature zone 1), the temperature of the porcelain boat 1 region was controlled at 625°C, and the temperature of the constant temperature zone 2 was controlled at 340°C. Subsequently, the carrier gas was changed and the volatilized Te and Ge raw materials were carried to the downstream surface of the WSe2 two-dimensional material for chemical vapor deposition under the carrier gas. The carrier gas was Ar-H2; the flow rates were Ar 80 sccm and H2 8 sccm, respectively, and the chemical deposition time was 10 minutes.

[0135] The optical schematic diagram is shown in Figure 22. The α-GeTe nanosheets prepared by CVD show the coexistence of multiple phases, and the vertical scale is much larger than the lateral size. Figure 22 The scale bar in the figure is 10 μm.

[0136] 2. Preparation of field effect transistors and their application in two-dimensional materials

[0137] Example 2-1

[0138] The method for preparing an α-GeTe field effect transistor is to deposit metal Cr (10 nm) / Au (50 nm) on an α-GeTe nanosheet prepared by PVD (the material prepared in Example 1-1) using electron beam exposure to obtain an α-GeTe field effect transistor.

[0139] Example 2-2

[0140] The preparation method of the α-GeTe / WSe2 field effect transistor is as follows: metal Cr (10nm) / Au (50nm) is deposited on the α-GeTe nanosheets (material prepared in Example 1-1) prepared by the PVD method using electron beam exposure to obtain an α-GeTe contact WSe2 field effect transistor.

[0141] Comparative Example 2-1

[0142] The method for preparing a WSe2 field-effect transistor differs from that in Example 2-1 only in that α-GeTe is not formed on the surface of the WSe2 two-dimensional material; instead, the transistor is fabricated directly on the WSe2 surface. Other device preparation and parameters are the same as in Example 2-1.

[0143] Figure 23Schematic diagram of α-GeTe field-effect transistor for implementation of Example 2-1;

[0144] Figure 24 For implementation 2-1, the output curve of α-GeTe field effect transistor;

[0145] Figure 25 For implementation 2-1, transfer curve of α-GeTe field effect transistor;

[0146] Figure 26 To implement the conductivity statistics of 2-1α-GeTe field effect transistors;

[0147] Figure 27 To implement the breakdown voltage curve of 2-1α-GeTe field effect transistor;

[0148] Figure 28 Schematic diagram of a WSe2 field effect transistor with α-GeTe as the metal electrode in Example 2-2;

[0149] Figure 29 This is an optical image of a WSe2 field-effect transistor with α-GeTe as the metal electrode in Example 2-2;

[0150] Figure 30 The output curve of the WSe2 field effect transistor with comparative example 2-2α-GeTe as the metal electrode;

[0151] Figure 31 The transfer curve of the WSe2 field effect transistor with comparative example 2-2α-GeTe as the metal electrode;

[0152] Figure 32 Schematic diagram of a WSe2 field effect transistor with comparative example 2-1Cr / Au as the metal electrode;

[0153] Figure 33 This is an optical schematic diagram of a WSe2 field-effect transistor with comparative example 2-1Cr / Au as the metal electrode;

[0154] Figure 34 The output curve of the WSe2 field effect transistor with Cr / Au as the metal electrode in comparative example 2-1;

[0155] Figure 35 The output curve of the WSe2 field effect transistor with Cr / Au as the metal electrode in comparative example 2-1;

[0156] The electrical study of the field effect transistor above demonstrates that α-GeTe has good conductivity and ultra-high breakdown voltage. By comparing Example 2-2 with Comparative Example 2-1, the performance of the field effect transistor with α-GeTe as the metal electrode has been greatly improved, with the on-state current density increasing from 7.83 μA / μm to 23.86 μA / μm, and the electron mobility increasing from 16.5 cm 2 V -1 S -1 Increase to 75.0cm 2 V -1 S -1 ) demonstrated the enhancement of WSe2 field-effect transistor performance by using α-GeTe as a metal electrode.

Claims

1. A PVD preparation method for α-GeTe two-dimensional material, characterized by: volatilize GeTe raw materials at 600-700°C; physically vapor deposit the volatilized raw materials on a substrate surface without dangling bonds at a deposition temperature of 340-380°C in a hydrogen-containing carrier gas to produce α-GeTe two-dimensional materials; The hydrogen-containing carrier gas is a mixture of hydrogen and a protective atmosphere, wherein the flow rate of hydrogen is 1-10 sccm and the flow rate of the protective atmosphere is 70-90 sccm.

2. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: The volatilization temperature of GeTe raw materials is 620~675℃.

3. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: The volatilization temperature of GeTe raw materials is 620~630℃.

4. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: The purity of the GeTe raw material is greater than or equal to 99%.

5. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: The purity of the GeTe raw material is greater than or equal to 99.9%.

6. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: In the hydrogen-containing carrier gas, the protective atmosphere is at least one of nitrogen and an inert gas.

7. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: The flow rate of hydrogen in the hydrogen-containing carrier gas is 2~8 sccm.

8. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: The flow rate of the protective atmosphere is 75~85 sccm.

9. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: The temperature of the heated volatilization area is 620~675℃.

10. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: The temperature of the heated volatilization area is 620~630℃.

11. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: The temperature in the physical vapor deposition area is 340~360℃.

12. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: The physical vapor deposition time is 5~15 min.

13. The PVD preparation method of α-GeTe two-dimensional material according to claim 1, characterized in that: Mica or two-dimensional material substrates without dangling bonds; The two-dimensional material substrate is a substrate on which MX2 two-dimensional material is deposited.

14. The PVD preparation method of α-GeTe two-dimensional material according to claim 13, characterized in that: The M in MX2 two-dimensional materials is a transition metal element.

15. The PVD preparation method of α-GeTe two-dimensional material according to claim 14, characterized in that: The M is at least one of Mo and W.

16. The PVD preparation method of α-GeTe two-dimensional material according to claim 13, characterized in that: X in the MX2 two-dimensional material is at least one of S and Se.

17. The PVD preparation method of α-GeTe two-dimensional material according to claim 13, characterized in that: The substrate without dangling bonds has a flat surface.

18. The PVD preparation method of α-GeTe two-dimensional material according to claim 13, characterized in that: In the two-dimensional material substrate, the planar size of the two-dimensional material is greater than or equal to 50 um.

19. The PVD preparation method of α-GeTe two-dimensional material according to claim 18, characterized in that: In the two-dimensional material substrate, the planar size of the two-dimensional material is greater than or equal to 200 um.

20. An α-GeTe two-dimensional material prepared by the preparation method according to any one of claims 1 to 19.

21. An application of an α-GeTe two-dimensional material prepared by the preparation method according to any one of claims 1 to 19, characterized in that: It is used to prepare micro-nanoelectronic devices.

22. Use of the α-GeTe two-dimensional material prepared by the preparation method according to claim 21, characterized in that: The micro-nano electronic device is a field effect transistor.

23. Use of the α-GeTe two-dimensional material prepared by the preparation method according to claim 22, characterized in that: The preparation steps of field effect transistor are: The sample was marked on the surface of an α-GeTe two-dimensional nanosheet on a substrate without dangling bonds using electron beam exposure, and then metal was deposited on its surface to obtain a field-effect transistor.

24. Use of the α-GeTe two-dimensional material prepared by the preparation method according to claim 23, characterized in that: Depositing metal on the surface of α-GeTe nanosheets using a vacuum coating machine; The metals are Cr and Au.

25. A field effect transistor device, characterized in that: The invention relates to an α-GeTe two-dimensional material prepared by the preparation method according to any one of claims 1 to 19, or prepared from the α-GeTe two-dimensional material.

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