阅读说明：本技术 一种插入二维半导体硒化铟纳米片改善二维过渡金属硫族化合物电接触的方法 (Method for improving electrical contact of two-dimensional transition metal chalcogenide by inserting two-dimensional semiconductor indium selenide nanosheets ) 是由 李洋 徐成彦 徐博 甄良 于 2020-05-21 设计创作，主要内容包括：一种插入二维半导体硒化铟纳米片改善二维过渡金属硫族化合物电接触的方法。本发明属于电子和光电子领域。本发明是要解决现有改善TMDs电接触方法改善效果不明显,以及绝缘插入层厚度严格受限的技术问题。本发明方法如下：一、通过机械剥离方法制备TMDs层,通过干法转移将TMDs层转移到清洗干净的SiO-(2)/Si衬底上的SiO-(2)一侧,然后进行退火处理；二、通过机械剥离方法制备InSe纳米片层,然后通过光学显微镜和原子力显微镜选择所需厚度的InSe纳米片层,并通过干法转移将InSe纳米片层转移至步骤一后的TMDs层上,然后进行退火处理,退火后自然冷却至室温,得到InSe与TMDs的异质结。本发明的方法简单有效,不同于其他插入的绝缘层必须严格地限制在1-3nm之内,可有效地改善TMDs的电接触。(A method for improving electrical contact of a two-dimensional transition metal chalcogenide by inserting a two-dimensional semiconductor indium selenide nanosheet. The present invention is in the field of electronics and optoelectronics. The invention aims to solve the technical problems that the improvement effect of the existing TMDs (transition metal oxide semiconductors) electric contact improvement method is not obvious, and the thickness of an insulating insertion layer is strictly limited. The method comprises the following steps: firstly, preparing a TMDS layer by a mechanical stripping method, and transferring the TMDS layer to cleaned SiO by dry transfer 2 SiO on/Si substrate 2 One side is then annealed; and secondly, preparing an InSe nanosheet layer by a mechanical stripping method, selecting the InSe nanosheet layer with the required thickness through an optical microscope and an atomic force microscope, transferring the InSe nanosheet layer to the TMDS layer obtained in the first step through dry transfer, then annealing, and naturally cooling to room temperature after annealing to obtain the heterojunction of InSe and TMDS. The method of the inventionThe method is simple and effective, and different from other inserted insulating layers which are strictly limited within 1-3nm, the electrical contact of TMDs can be effectively improved.)

1. A method for inserting a two-dimensional semiconductor indium selenide nanosheet to improve electrical contact of a two-dimensional transition metal chalcogenide is characterized by comprising the following steps:

firstly, preparing a TMDS layer by a mechanical stripping method, and transferring the TMDS layer to cleaned SiO by dry transfer₂SiO on/Si substrate₂One side of the glass is annealed, and the glass is naturally cooled to room temperature for later use after annealing;

and secondly, preparing an InSe nanosheet layer by a mechanical stripping method, selecting the InSe nanosheet layer with the required thickness by an optical microscope and an atomic force microscope, transferring the InSe nanosheet layer to the TMDS layer obtained in the first step by dry transfer, then annealing, naturally cooling to room temperature after annealing to obtain a heterojunction of InSe and TMDS, and finishing the improvement of the electrical contact of the two-dimensional transition metal chalcogenide.

2. The method of claim 1, wherein in step one, the TMDs are n-MoS₂Or p-WSe₂。

3. The method for improving the electrical contact of the two-dimensional transition metal chalcogenide by inserting the two-dimensional semiconductor indium selenide nanosheets as claimed in claim 1, wherein the mechanical exfoliation method in the first step is specifically carried out by: taping n-MoS₂Or p-WSe₂And pressing to thin the film, and then adhering the film on a glass slide with a PDMS film, thereby obtaining the TMDS layer on the PDMS film.

4. The method for inserting two-dimensional semiconductor indium selenide nanosheets to improve electrical contact of a two-dimensional transition metal chalcogenide as claimed in claim 1, wherein in step one the TMDs layer has a thickness of 14nm to 16nm, a length of 20 μ ι η to 100 μ ι η, and a width of 20 μ ι η to 100 μ ι η.

5. The method of claim 1, wherein the thickness of the TMDs layer in step one is 15 nm.

6. The method for improving the electrical contact of the two-dimensional transition metal chalcogenide by inserting the two-dimensional semiconductor indium selenide nanosheets as claimed in claim 1, wherein the mechanical exfoliation method in the second step comprises the specific processes of: and (3) sticking the InSe block body by using an adhesive tape, pressing to thin the InSe block body, and sticking the InSe block body on a glass slide stuck with a PDMS film to obtain the InSe nanosheet layer on the PDMS film.

7. The method for improving the electrical contact of the two-dimensional transition metal chalcogenide by inserting the two-dimensional semiconductor indium selenide nanosheets as recited in claim 1, wherein the thickness of the InSe nanosheet layer in step two is from 4nm to 12 nm.

8. The method of claim 1, wherein the tape in steps one and two is a blue film tape.

9. The method for improving the electrical contact of the two-dimensional transition metal chalcogenide by inserting the two-dimensional semiconductor indium selenide nanosheets as claimed in claim 1, wherein the annealing treatment in the first step and the second step is performed under specific conditions of: argon atmosphere, gas flow of 15 sccm-25 sccm, heating rate of 4 ℃/min-6 ℃/min, heating to 300-330 ℃ for 1.5-2.5 h.

10. The method for improving the electrical contact of the two-dimensional transition metal chalcogenide by inserting the two-dimensional semiconductor indium selenide nanosheets as claimed in claim 1, wherein the annealing treatment in the first step and the second step is performed under specific conditions of: argon atmosphere, gas flow of 20sccm, heating rate of 5 ℃/min, heating to 310-320 ℃ for 2 h.

Technical Field

The present invention is in the field of electronics and optoelectronics; in particular to a method for improving the electrical contact of a two-dimensional transition metal chalcogenide by inserting a two-dimensional semiconductor indium selenide nanosheet.

Background

Two-dimensional transition metal chalcogenides (TMDs) have bright application in the electronic and optoelectronic fields due to their special physical properties, but their performance is severely limited by the large contact barrier between TMDs and the electrode material. In order to improve the performance of two-dimensional TMDs functional devices (e.g., field effect transistors, phototransistors, etc.), it is very important to effectively reduce the contact barrier between TMDs and metal electrodes.

To date, many methods have been reported in the literature to improve the electrical contact behavior of TMDs, including selecting metals with suitable work functions as electrodes, chemical doping of TMDs (chemical doping), one-dimensional edge contact (edge-contact), direct chemical vapor deposition to produce graphene-TMDs or 2D metal-TMDs heterostructures, phase engineering, insertion of ultra-thin metal oxide layers between metal electrodes and TMDs materials, or hexagonal boron nitride. Although the above method has been shown to improve the behavior of electrical contacts to some extent, there are several challenges. For example, due to the strong fermi level pinning effect between metals and TMDs, the Schottky-Mott limit cannot effectively guide the selection of metals of different work functions as electrodes to effectively lower the contact barrier between them and TMDs; the degenerate doping of TMDs by chemical methods can reduce the barrier width and improve the electron injection efficiency, but its stability and durability need to be improved; phase engineering and direct growth of 2D metal-TMDs planar junctions can result in continuous hetero-or homojunctions with relatively small barriers in the device, but their utility may not be apparent when the fermi level depth of the 2D metal is between the valence and conduction bands of the TMDs material, in addition to which the fabrication process remains challenging.

In addition to the above, a tunneling layer, such as wide band gap Al, is interposed between the metal electrode and the TMDS channel material₂O₃、Ta₂O₅、TiO₂h-BN, etc., can effectively alleviate the heterojunction interfaceFermi level pinning, and lowering contact barrier by reducing metal induced band gap states and interfacial dipoles. This approach also has its limitations. First, this approach lowers the contact barrier by trading off the schottky barrier against the tunneling barrier, so the thickness of the inserted metal oxide or h-BN is severely limited to 1-3 nm. Due to the hydrophobic nature of TMDs, it is challenging to grow metal oxides of desired thickness precisely and uniformly on their surfaces by atomic layer deposition or other vapor deposition methods, during which TMDs films may also damage their original structure at high temperatures. Likewise, the thickness of the h-BN nanosheets is limited to single and double layers, and both exfoliation and growth are extremely challenging. Second, the relatively high conduction band and low valence band of metal oxides and h-BN may increase the tunneling resistance of n-type or p-type TMDS transistors.

Disclosure of Invention

The invention provides a method for improving two-dimensional transition metal chalcogenide (TMDS) electric contact by inserting a two-dimensional semiconductor indium selenide (InSe) nanosheet, aiming at solving the technical problems that the existing method for improving TMDs electric contact is not obvious in improvement effect and the thickness of an insulating insertion layer is strictly limited.

The method for improving the electrical contact of the two-dimensional transition metal chalcogenide by inserting the two-dimensional semiconductor indium selenide nanosheets is carried out according to the following steps:

firstly, preparing a TMDS layer by a mechanical stripping method, and transferring the TMDS layer to cleaned SiO by dry transfer₂SiO on/Si substrate₂One side of the glass is annealed, and the glass is naturally cooled to room temperature for later use after annealing;

and secondly, preparing an InSe nanosheet layer by a mechanical stripping method, selecting the InSe nanosheet layer with the required thickness by an optical microscope and an atomic force microscope, transferring the InSe nanosheet layer to the TMDS layer obtained in the first step by dry transfer, then annealing, naturally cooling to room temperature after annealing to obtain a heterojunction of InSe and TMDS, and finishing the improvement of the electrical contact of the two-dimensional transition metal chalcogenide.

Further limiting, in the step one, the TMDs are n-MoS₂Or p-WSe₂。

Further limiting, the mechanical stripping method in the first step specifically comprises the following steps: taping n-MoS₂Or p-WSe₂And pressing to thin the film, and then adhering the film on a glass slide with a PDMS film, thereby obtaining the TMDS layer on the PDMS film.

Further limiting, in the step one, the thickness of the TMDS layer is 14 nm-16 nm, the length is 20 μm-100 μm, and the width is 20 μm-100 μm.

Further, the thickness of the TMDS layer in the first step is 15 nm.

Further limiting, the mechanical stripping method in the second step comprises the following specific processes: and (3) sticking the InSe block body by using an adhesive tape, pressing to thin the InSe block body, and sticking the InSe block body on a glass slide stuck with a PDMS film to obtain the InSe nanosheet layer on the PDMS film.

Further limiting, the thickness of the InSe nanosheet layer in the second step is 4nm to 12 nm.

Further limiting, in the first step, the adhesive tape is a blue film adhesive tape.

Further limiting, in the second step, the adhesive tape is a blue film adhesive tape.

Further, the specific conditions of the annealing treatment in the step one are as follows: argon atmosphere, gas flow of 15 sccm-25 sccm, heating rate of 4 ℃/min-6 ℃/min, heating to 300-330 ℃ for 1.5-2.5 h.

Further, the specific conditions of the annealing treatment in the step one are as follows: argon atmosphere, gas flow of 20sccm, heating rate of 5 ℃/min, heating to 310-320 ℃ for 2 h.

Further limiting, the specific conditions of the annealing treatment in the step two are as follows: argon atmosphere, gas flow of 15 sccm-25 sccm, heating rate of 4 ℃/min-6 ℃/min, heating to 300-330 ℃ for 1.5-2.5 h.

Further limiting, the specific conditions of the annealing treatment in the step two are as follows: argon atmosphere, gas flow of 20sccm, heating rate of 5 ℃/min, heating to 310-320 ℃ for 2 h.

Compared with the prior art, the invention has the remarkable effects as follows:

(1) the invention adopts the modes of mechanical stripping and dry method transfer to cover the indium selenide on the TMDs sheet layer material, the method is simple, and the improvement effect on TMDs electric contact is obvious.

(2) The InSe insertion layer adopted by the invention is not strictly limited to the ultrathin thickness of 1-3nm, and the insulating InSe insertion layer of 4-12nm can reduce the contact barrier of TMDS transistors. With the maturity of the technology of growing large-area defect-rich InSe-TMDs by CVD, the method has bright application prospect in large-scale preparation of heterojunction devices with low contact barriers.

Drawings

FIG. 1 shows InSe and n-MoS according to one embodiment₂Schematic structural diagram of the device prepared by the heterojunction of (1); wherein 1-Si, 2-SiO₂3-TMDS layer, 4-InSe nano sheet layer, 5-source electrode and 6-drain electrode;

FIG. 2 is an optical photograph of a verification device in a verification test in which a region a is n-MoS₂Layer, zone b is an InSe nanosheet layer;

FIG. 3 is a graph of the effective Schottky barrier height versus gate voltage corresponding to FIG. 2;

FIG. 4 is a graph of the thickness of the InSe insulator layer inserted into the device versus the effective Schottky barrier of the device in one through five embodiments;

FIG. 5 is an optical photograph of a verification device in a verification test in which region a is p-WSe₂Layer, zone b is an InSe nanosheet layer;

fig. 6 is a graph of the effective schottky barrier height versus gate voltage for the circuit of fig. 5.

Detailed Description

The first embodiment is as follows: the method for improving the electrical contact of the two-dimensional transition metal chalcogenide by inserting the two-dimensional semiconductor indium selenide nanosheets in the embodiment is carried out according to the following steps:

firstly, preparing a TMDS layer by a mechanical stripping method, wherein the mechanical stripping method comprises the following specific steps: taping n-MoS₂Pressing, folding in half after pressing, and repeating folding in half and pressing 3Then, the film was thinned and then adhered to a glass slide to which a PDMS film was attached to obtain n-MoS having a thickness of 15nm and a length X width of 90 μm X10 μm on the PDMS film₂Layer of n-MoS on PDMS film by dry transfer₂Layer transfer to cleaned SiO₂SiO on/Si substrate₂One side of the substrate is then annealed, and the specific conditions are as follows: argon atmosphere, gas flow of 20sccm, heating rate of 5 ℃/min, heating to 310 ℃ for 2 h. Naturally cooling to room temperature after annealing for later use;

secondly, preparing an InSe nanosheet layer by a mechanical stripping method, wherein the mechanical stripping method comprises the following specific steps: sticking the InSe block body by using an adhesive tape and pressing, folding the InSe block body in half after pressing, repeatedly folding and pressing for 3 times to thin the InSe block body, sticking the InSe block body on a glass slide stuck with a PDMS film to obtain an InSe nanosheet layer on the PDMS film, selecting the InSe nanosheet layer with the thickness of 4.2nm through an optical microscope, and transferring the InSe nanosheet layer on the PDMS film to the n-MoS obtained in the first step through dry transfer₂And (3) carrying out annealing treatment on the layer, wherein the specific conditions are as follows: argon atmosphere, gas flow of 20sccm, heating rate of 5 ℃/min, heating to 310 ℃ for 2 h. Naturally cooling to room temperature after annealing to obtain InSe and n-MoS₂The improvement of the electrical contact of the two-dimensional transition metal chalcogenide is accomplished.

To verify the effect of the present embodiment, InSe and n-MoS obtained by the present embodiment were used₂The heterojunction is prepared into a device, and the specific process is as follows:

InSe and n-MoS obtained in the first embodiment by means of electron beam Exposure (EBL)₂The obtained device structure is shown in figure 1, and in order to eliminate the influence factors introduced by the device preparation process, the InSe insertion layer pair MoS is determined singly₂Influence of electrical contact, we prepared a verification device (10 μm on the scale) as shown in FIG. 2, which contained both MoS alone₂And electrodes, in turn, included in MoS₂And an InSe portion interposed between the electrodes, and in addition, the device also included a separate InSe portion in order to demonstrate the insulating properties of the InSe used.

For InSe and n-MoS of the first embodiment₂The device prepared by the heterojunction is subjected to electrical property analysis to obtain an effective Schottky barrier curve chart shown in figure 3, and the graph shows that MoS alone₂The effective Schottky barrier height of the device is 156meV, while at MoS₂After 4.2nm thick insulating InSe was inserted between the electrodes, the effective schottky barrier height was significantly reduced to 44meV, while InSe alone was also measured and the test results demonstrated its insulating properties.

The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: and in the second step, the thickness of the InSe nano sheet layer is 5.5 nm. Other steps and parameters are the same as those in the first embodiment.

The third concrete implementation mode: the first difference between the present embodiment and the specific embodiment is: and in the second step, the thickness of the InSe nanosheet layer is 7 nm. Other steps and parameters are the same as those in the first embodiment.

The fourth concrete implementation mode: the first difference between the present embodiment and the specific embodiment is: and in the second step, the thickness of the InSe nanosheet layer is 9 nm. Other steps and parameters are the same as those in the first embodiment.

The fifth concrete implementation mode: the first difference between the present embodiment and the specific embodiment is: and in the second step, the thickness of the InSe nano sheet layer is 12 nm. Other steps and parameters are the same as those in the first embodiment.

And (3) detection: the relationship between the thickness of the InSe insulating layer and the effective schottky barrier of the device was examined in embodiments one through five to obtain a graph as shown in fig. 4, from which it can be seen that in MoS₂The effective schottky barrier height was significantly reduced to 44meV with the insertion of a 4.2nm thick insulating InSe nanosheet between the layers and the electrode. In MoS₂The effective schottky barrier height was significantly reduced to 38meV with the 5.5nm thick insulating InSe nanosheets interposed between the layers and the electrodes. In MoS₂The effective schottky barrier height was significantly reduced to 36meV with a 7nm thick insulating InSe nanosheet layer interposed between the layers and the electrode. In MoS₂With 9nm thick insulation interposed between the layers and the electrodesAfter the InSe nanosheet, its effective schottky barrier height was significantly reduced to 50 meV. In MoS₂The effective schottky barrier height was significantly reduced to 55meV with a 12nm thick insulating InSe nanosheet layer interposed between the layers and the electrode.

The sixth specific implementation mode: the method for improving the electrical contact of the two-dimensional transition metal chalcogenide by inserting the two-dimensional semiconductor indium selenide nanosheets in the embodiment is carried out according to the following steps:

preparing the TMDS layer by a mechanical stripping method, wherein the mechanical stripping method comprises the following specific steps: taping p-WSe₂Pressing, folding, doubling again for 3 times, thinning, and sticking on the glass slide with PDMS film to obtain p-WSe with thickness of 15nm, length of 70 μm and width of 20 μm₂Layer, p-WSe on PDMS film by dry transfer₂Layer transfer to cleaned SiO₂SiO on/Si substrate₂One side of the substrate is then annealed, and the specific conditions are as follows: argon atmosphere, gas flow of 20sccm, heating rate of 5 ℃/min, heating to 310 ℃ for 2 h. Naturally cooling to room temperature after annealing for later use;

fourthly, preparing the InSe nano sheet layer by a mechanical stripping method, wherein the mechanical stripping method comprises the following specific steps: sticking the InSe block body with an adhesive tape, pressing, folding, repeatedly folding and pressing for 3 times to thin the InSe block body, sticking the InSe block body on a glass slide stuck with a PDMS film to obtain an InSe nanosheet layer on the PDMS film, selecting the InSe nanosheet layer with the thickness of 12nm through an optical microscope, and transferring the InSe nanosheet layer on the PDMS film to the p-WSe obtained in the first step through dry transfer₂And (3) carrying out annealing treatment on the layer, wherein the specific conditions are as follows: argon atmosphere, gas flow of 20sccm, heating rate of 5 ℃/min, heating to 310 ℃ for 2 h. Naturally cooling to room temperature after annealing to obtain InSe and p-WSe₂The improvement of the electrical contact of the two-dimensional transition metal chalcogenide is accomplished.

To verify the effects of the present embodiment, InSe and p-WSe obtained by the present embodiment were used₂Is prepared into a device, in particularThe process is as follows:

InSe and p-WSe obtained in the sixth embodiment by means of electron beam Exposure (EBL)₂In order to eliminate influence factors introduced by a device preparation process, the pair of WSe of the InSe insertion layer is determined singly₂Influence of electrical contact, we prepared a verification device (10 μm scale) as shown in FIG. 5, which contained both WSe alone₂And electrodes, in turn comprised in WSe₂And an InSe portion interposed between the electrodes, and in addition, the device also included a separate InSe portion in order to demonstrate the insulating properties of the InSe used.

InSe and WSe of the sixth embodiment₂The device prepared by the heterojunction is subjected to electrical property analysis to obtain an effective Schottky barrier curve chart shown in figure 6, and the graph shows that the WSe alone₂The effective Schottky barrier height of the device is 95meV, while at WSe₂After 12nm thick insulating InSe was inserted between the electrodes, the effective schottky barrier height was significantly reduced to 16meV, while InSe alone was also measured and the test results demonstrated its insulating properties.