Method for regulating metal-semiconductor contact by using interlayer electric dipole

Abstract

The invention discloses a method for regulating and controlling metal-semiconductor contact by using an interlayer electric dipole. The method comprises the following steps of: providing a two-dimensional Van der Waals superlattice metal material and a two-dimensional semiconductor; testing the direction of a dipole on the surface of the two-dimensional Van der Waals superlattice metal material; the termination surface of the two-dimensional Van der Waals superlattice metal material is switched through mechanical stripping according to needs; a required two-dimensional Van der Waals superlattice metal material is contacted with a two-dimensional semiconductor, and metal-semiconductor contact is regulated and controlled by utilizing an electric dipole between the two-dimensional Van der Waals superlattice metal material and the two-dimensional semiconductor.

Description

Technical Field

[0001] The invention relates to a method for regulating metal-semiconductor contact by using interlayer electric dipoles. Background Art

[0002] Two-dimensional materials with high carrier mobility, such as graphene, black phosphorus, and transition metal dichalcogenides (TMDCs), are considered promising candidates for next-generation semiconductor devices due to their layered structures and smooth surfaces without dangling bonds. However, the metal electrodes on 2D semiconductors significantly impact the performance of 2D electronic devices. Tuning the interfacial Schottky barrier is a significant issue, as it is severely affected by the Fermi level pinning effect (FLPE) at the contact, not only in conventional semiconductors but also in 2D semiconductors. Important research advances have shown that van der Waals (vdW) contacts can effectively address this issue by suppressing metal-induced gap states (MIGS) and thus reducing the FLPE. In addition to transferring metal films or 2D metal materials onto 2D semiconductors, vdW contacts can also be obtained by growing high-quality 2D metal TMDCs on 2D semiconductors. These techniques enable the design of optimal Schottky barrier heights, holding great promise for applications in low-dimensional devices. 2D transistors with low contact resistance can be realized using VS2 / MoSe2 vdW contacts or WTe2 / WSe2 vdW contacts. In addition, Au / WSe2 and Pt / MoS2 van der Waals contacts can be used to obtain Schottky junctions with rectifying properties. The huge potential of van der Waals contacts makes it of great significance and value to explore new methods to design van der Waals contact interfaces.

[0003] Two-dimensional van der Waals superlattice (vdWSL) will bring more opportunities for van der Waals contact engineering. Two-dimensional vdWSL is formed by alternating stacking of sulfide blocking layers and TMDC layers in the c-axis direction. Compared with traditional TMDC, the interlayer coupling between TMDC layers is weakened in vdWSL, and the interlayer interaction between additional TMDC layers and blocking layers is introduced. For example, (PbSe) 1.14 The PbSe barrier layer in NbSe2 leads to a unique two-dimensional electronic structure and anisotropic superconductivity. (BiSe) 1.09 The BiSe blocking layer in TaSe2 reduces the thermal conductivity, resulting in a very low Seebeck coefficient and charge density wave phenomena. Due to the charge transfer between the TMDC layer and the blocking layer, more unique physical properties can be verified in vdWSL. 1.5 ] 1.15In NbS₂, the valence change of Eu ions caused by charge transfer between the NbS₂ layer and the EuS barrier layer leads to the unique magnetic structure. Furthermore, charge transfer between the barrier layer and the TMDC layer is extensive in the vdWSL, leading to efficient carrier doping into the TMDC layer, with a doping concentration comparable to that induced by the ionic liquid.

[0004] However, an important but neglected degree of freedom in vdWSLs is the interlayer dipole induced by charge transfer. Summary of the Invention

[0005] In view of this, it is indeed necessary to provide a method to regulate metal-semiconductor contacts using interlayer electric dipoles.

[0006] A method for regulating metal-semiconductor contact using interlayer electric dipoles comprises the following steps: providing a two-dimensional van der Waals superlattice metal material and a two-dimensional semiconductor; testing the surface dipole direction of the two-dimensional van der Waals superlattice metal material; switching the termination surface of the two-dimensional van der Waals superlattice metal material by mechanical peeling as needed; bringing the required two-dimensional van der Waals superlattice metal material into contact with the two-dimensional semiconductor, and regulating the metal-semiconductor contact using the electric dipole between the two-dimensional van der Waals superlattice metal material and the two-dimensional semiconductor.

[0007] Compared to existing technologies, the method provided by this invention, which uses interlayer electric dipoles to regulate metal-semiconductor contact, can switch the termination surface of a two-dimensional van der Waals superlattice metal material through mechanical exfoliation. The surface dipoles of different termination surfaces are oriented inward or outward. This switchable surface dipole has a strong modulating effect on the work function of the two-dimensional van der Waals superlattice metal material. The two-dimensional van der Waals superlattice metal material and the two-dimensional semiconductor form a Schottky junction that can produce two types of rectifying effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 a is a two-dimensional metal vdWSL Ba6Ta provided in an embodiment of the present invention 11 S 28 TEM photo of .

[0009] Figure 1 b is a two-dimensional metal vdWSL Ba6Ta provided in an embodiment of the present invention 11 S 28 Schematic diagram of the lattice structure and interlayer dipoles along the a-axis.

[0010] Figure 1 c is the two-dimensional metal vdWSL Ba6Ta provided by an embodiment of the present invention 11 S 28The resistivity of Ba6Ta is plotted against temperature. The inset shows the 11 S 28 Optical image of the crystal.

[0011] Figure 1 d and Figure 1 e is the two-dimensional metal vdWSL Ba6Ta provided in an embodiment of the present invention 11 S 28 The electron potential energy for the two types of termination surfaces.

[0012] Figure 1 f is a diagram of two Ba6Ta wafers arranged on the SiO2 / Si wafer provided in an embodiment of the present invention. 11 S 28 KPFM image.

[0013] Figure 2 a is Ba6Ta provided in the embodiment of the present invention 11 Schematic diagram of the S28 / WSe2 Schottky junction device and external circuitry.

[0014] Figure 2 b is the transfer curve of the bipolar WSe2 provided in an embodiment of the present invention, where a bias voltage of 0.4 V is applied to device 1 and a bias voltage of 3.0 V is applied to device 2.

[0015] Figure 2 c and Figure 2 f are the optical images of device 1 and device 2, respectively.

[0016] Figure 2 d and Figure 2 g are the IV contour plots of device 1 and device 2, respectively.

[0017] Figure 2 e and Figure 2 h is the output curve of device 1 and device 2 when VG = -40V and +40V respectively.

[0018] Figure 3 a is a schematic diagram of scanning photocurrent microscopy (SPCM) measurement of a two-dimensional transistor device.

[0019] Figure 3 b and Figure 3 c is the optical image of the SPCM area with a size of 10 × 10 μm for device 1 and device 2.

[0020] Figure 3 d and Figure 3 e is the SPCM images of device 1 and device 2.

[0021] Figure 4 a and Figure 4b are the band alignments of device 1 and device 2 before and after contact, respectively.

[0022] Figure 4 c Band diagram explaining the SPCM measurement results.

[0023] Figure 5 It is a two-dimensional van der Waals superlattice metal material (LaSe) 1.14 Crystal structure of (NbSe2)2.

[0024] Figure 6 It is a two-dimensional van der Waals superlattice metal material (PbSe) 1.14 Crystal structure of NbSe2.

[0025] Figure 7 It is a two-dimensional van der Waals superlattice metal material [(EuS) 1.5 ] 1.15 Crystal structure of NbS2.

[0026] Figure 8 Ba6Nb is a two-dimensional van der Waals superlattice metal material 11 S 28 crystal structure.

[0027] Description of main component symbols

[0028] none

[0029] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0030] The method for regulating metal-semiconductor contact by using interlayer electric dipoles provided by the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] See Figure 1 The present invention provides a method for regulating metal-semiconductor contact by using interlayer electric dipoles. The method for regulating metal-semiconductor contact by using interlayer electric dipoles comprises the following steps:

[0032] Provide one- and two-dimensional van der Waals superlattice metal materials and two-dimensional semiconductors;

[0033] Test the surface dipole direction of two-dimensional van der Waals superlattice metal materials;

[0034] Switching the termination surface of the two-dimensional van der Waals superlattice metal material by mechanical exfoliation as needed;

[0035] The required two-dimensional van der Waals superlattice metal material is brought into contact with a two-dimensional semiconductor, and the electric dipole between the two-dimensional van der Waals superlattice metal material and the two-dimensional semiconductor is used to regulate the metal-semiconductor contact.

[0036] Specifically, this embodiment provides a method for controlling the two-dimensional metal vdWSL Ba6Ta by using interlayer electric dipoles. 11 S 28 (BTS) method for contacting with two-dimensional semiconductor WSe2.

[0037] Step 1: Provide a two-dimensional metal vdWSL Ba6Ta 11 S 28 (BTS) crystal and two-dimensional semiconductor WSe2. WSe2 is a typical two-dimensional bipolar semiconductor with high electron and hole mobility. BTS crystal is synthesized by molten salt method, such as Figure 1 As shown in the inset of c, the BTS crystal is silvery white, with a diameter of about 1.5 mm and a thickness of less than 0.1 mm. The lattice structure was analyzed using high spatial resolution TEM observation along the a-axis of the crystal, as shown in Figure 1 As shown in a. The BTS crystal consists of a superlattice structure consisting of Ba3TaS5 layers and TaS2 layers, where Ba3TaS5 is a barrier layer and TaS2 is a TMDC layer. The thickness of the Ba3TaS5 layer is 0.86nm, and the lattice constant in the c-axis direction is 2.414nm. Transmission electron microscopy also shows that the BTS crystal is of high quality. The lattice structure of BTS can be further analyzed as follows. Figure 1 The resistivity-temperature curve was measured by the four-point probe method using a comprehensive physical property measurement system (QD ppms-14t). Figure 1 As shown in (c), the BTS crystal exhibits typical metallic properties with a resistivity of 1.2 mΩ·cm at 300 K. Below 2.6 K, the BTS crystal enters a superconducting state.

[0038] Step 2: Test the direction of the dipole on the BTS surface.

[0039] The function of the electron potential energy inside and on the surface of BTS in the c-axis direction is as follows Figure 1 d and 1e, where the Fermi level is set to 0 eV, and the potential energy of the vacuum region far from the BTS surface represents the vacuum energy level (Evc) of the corresponding surface. In the interior of the BTS, the electronic potential energy of the Ba3TaS5 layer is higher than that of the TaS2 layer, as shown in Figure 1As shown in d and 1e, more electrons are accumulated in the TaS2 layer. However, since BTS is electrically neutral, the Ba3TaS5 layer is positively charged, while the TaS2 layer is negatively charged. Therefore, an interlayer dipole is formed, and its direction is from the TaS2 layer to the Ba3TaS5 layer. It can be seen that the superlattice structure induces charge transfer between adjacent Ba3TaS5 layers and TaS2 layers and generates interlayer dipoles. The crystal has two possible mechanically exfoliated surfaces, namely the Ba3TaS55 termination surface and the TaS2 termination surface. The BTS surface is the surface dipole direction of the TaS2 layer inward, that is, toward the direction of the BTS, which is negative, and the BTS surface is the surface dipole direction of the Ba3TaS5 layer outward, that is, toward the direction outside the BTS, which is positive, as shown in Figure 1 As shown by the arrow in b. This example uses first-principles calculations to reveal the charge transfer and interlayer dipoles in BTS.

[0040] The surface dipole of BTS will have an important influence on its work function. The work function of a material is determined by the material itself and its surface dipole, i.e. W F =F-ep / ε0, where W F is the work function of the material, F is the work function of the material without surface dipole, p is the surface dipole density, and ε0 is the vacuum dielectric constant. The surface dipole of the BTS with the TaS2 layer on the surface is directed inward and is negative, and the surface dipole of the BTS with the Ba3TaS5 layer on the surface is directed outward and is positive. Therefore, the work function of the BTS with the TaS2 layer on the surface is higher than the work function of the BTS with the Ba3TaS5 layer on the surface. This conclusion can also be understood through a simplified physical image. The negative surface dipole introduces an additional interlayer electric field on the surface, which is directed outward. The dipole-induced surface electric field makes it more difficult for electrons to escape from the surface into the vacuum. Therefore, the negative surface dipole induces a higher work function. As for the positive surface dipole, the opposite is true. This principle can be explained by Figure 1 d and Figure 1 First-principles calculations (e) further confirm this. The work function can be calculated from the difference between the vacuum level and the Fermi level. The work functions of the BTS with a TaS2 surface layer and the BTS with a Ba3TaS5 surface layer are 5.88 eV and 2.19 eV, respectively. The work function of the TaS2 crystal is 4.8 eV, lower than that of the BTS with a TaS2 surface layer, indicating that surface dipoles do have a significant influence on the material's work function.

[0041] In addition, Kelvin probe microscopy (KPFM) was used to qualitatively study the potential difference between the two types of surfaces of BTS. Figure 1f shows a KPFM image of two BTS films with opposite surface dipoles, which were transferred to a SiO2 / Si substrate using polydimethylsiloxane (PDMS). The green and blue parts in the KPFM image represent the two BTS films. The potential inside each film is almost the same, indicating that a relatively uniform surface is obtained. The difference in the two colors indicates the surface potential difference between the two, which can be seen by moving the Figure 1 The V of the white arrow in f CPD Further verification. Since both flakes were peeled from the same BTS crystal, the different surface potentials are due to opposite surface dipoles. According to the KPFM measurement principle, the BTS on the left (green) has a larger work function than the BTS on the right (blue). Therefore, it can be inferred that the BTS surface on the left is a TaS2 layer (surface dipole facing inward, negative), while the right is a Ba3TaS5 layer (surface dipole facing outward, negative).

[0042] Therefore, the orientation of the BTS surface dipole can be determined by first-principles calculations or observed using Kelvin probe microscopy (KPFM).

[0043] Step 3: Switch the termination surface of the BTS by mechanical peeling as needed.

[0044] As mentioned above, the direction of the BTS surface dipole can be determined by first-principles calculations and the use of Kelvin probe microscopy (KPFM). If it is not the desired surface, the surface of the two-dimensional van der Waals superlattice metal material can be peeled off by mechanical peeling to expose a new surface, and then the above method can be used to determine the direction of the BTS surface dipole until it is the desired surface.

[0045] Step 4: Contact the required BTS with WSe2 and use the electric dipole between BTS and WSe2 to regulate the metal-semiconductor contact.

[0046] Based on the above calculations and tests, a two-dimensional transistor with a BTS contact electrode was designed and fabricated to demonstrate the effects caused by the presence of two surface dipoles. WSe2 was used as the two-dimensional semiconductor channel because it is a typical two-dimensional bipolar semiconductor with high electron and hole mobility. Calculations of the band structures of BTS and WSe2 indicate that BTS with a TaS2 surface layer or a Ba3TaS5 surface layer can be used in contact with WSe2 to inject holes or electrons into the channel. The device is fabricated by stacking a two-dimensional WSe2 film and a BTS film sequentially on a SiO2 / Si wafer. The BTS film is deposited on the WSe2 film surface using a dry transfer method. Figure 2Device c shows a two-dimensional transistor formed by a BTS film with a TaS2 layer on the surface and a WSe2 film, referred to as device 1. Specifically, a WSe2 film and a BTS film with a TaS2 layer on the surface are sequentially stacked on a SiO2 / Si wafer. The TaS2 layer of the BTS film is in contact with the WSe2 film. The BTS film has an electrode on its surface, and the WSe2 film also has an electrode. Figure 2 Figure f shows a two-dimensional transistor formed by a BTS film with a TBa3TaS5 layer on the surface and a WSe2 film, referred to as device 2. Specifically, a WSe2 film and a BTS film with a TBa3TaS5 layer on the surface are stacked sequentially on a SiO2 / Si wafer. The TBa3TaS5 layer of the BTS film is in contact with the WSe2 film. Electrodes are provided on the surface of the BTS film, and electrodes are provided on the WSe2 film. In devices 1 and 2, the electrodes provided on the WSe2 and BTS films serve as the source and drain, respectively. To test the intrinsic properties of the WSe2 film, an additional electrode can be provided on the WSe2 film, and the two electrodes on the WSe2 film can be used to test its intrinsic properties. The silicon in the SiO2 / Si wafer is p-doped silicon and serves as the global back gate (VG). The three electrodes are composed of 5nm Ti and 50nm Au (Ti / Au). It is understood that the three electrodes can also be made of other electrode materials, without limitation.

[0047] The Schottky contact between WSe2 film and BTS film was studied by electrical transport measurement. Figure 2 As shown in Figure 2b, the WSe2 channel in both devices exhibits typical ambipolar and near-neutral semiconductor characteristics, because the WSe2 channel can be turned on by positive or negative gate voltage (VG). When VG>0V, the carriers in the WSe2 channel are negative electrons, and when VG<0V, the carriers in the WSe2 channel are holes. Figure 2 The IV contour plots in d and 2g show the electrical transfer performance of the two devices, where the current (Ids) varies logarithmically with the bias voltage (Vds) and VG. The two devices have significant differences in electrical performance. The more obvious characteristics are the red colors in the first quadrant (+VG, +Vds) of device 1 and the third quadrant (-VG, -Vds) of device 2. Since the WSe2 channel exhibits typical bipolar behavior, the carrier type can be modulated by VG. Therefore, device 1 and device 2 exhibit rectification characteristics of electrons and holes, respectively. When device 1 is at VG = +40 V and device 2 is at VG = -40 V, its rectification ratio can reach 10 3 ,like Figure 2 e and 2h. It can be seen that two different types of Schottky diodes with different rectification modes have been realized by contacting the BTS film with the WSe2 film, which have high rectification ratios for electrons and holes, respectively.

[0048] Scanning photocurrent microscopy (SPCM) measurements further revealed the direction of the built-in electric field at the BTS / WSe2 contact interface. Figure 3 As shown in a, the SPCM image is drawn by scanning the junction with a focused laser beam and simultaneously recording the photocurrent and position. The area scanned by the SPCM is Figure 2 c and Figure 2 The dashed line in f outlines where the dimensions are 10 × 10 μm. Figure 3 b and 3c respectively Figure 2 c and Figure 2 f Enlarged image of the dotted box, where the dotted lines represent the boundaries between the two-dimensional material and the electrode. The boundaries of BTS, Ti / Au electrode, and WSe2 are represented by black, yellow, and blue dotted lines, respectively. Figure 3 d and Figure 3 e is the SPCM image of device 1 and device 2 under the same color scale, where the dotted line is Figure 3 b and Figure 3 The same as in c. Where VG is -40V~+40V, Vds=0V. The photocurrent of the device can be modulated by VG. In device 1, VG>0V( Figure 3 d) and VG<0V in device 2 ( Figure 3 e) generates a photocurrent, indicating the formation of a strong Schottky junction. Another notable phenomenon is that the two devices generate opposite photocurrents, as shown in the blue and red regions in the SPCM images. The opposing photocurrents further reveal two types of Schottky junctions, established by the opposite surface dipoles of the two BTS surfaces in contact with WSe2. Because the photocurrent and the built-in electric field are directed in the same direction, these SPCM images can reveal more information about the built-in electric field and charge transfer at the vdW contact interface. For device 1, the negative photocurrent at VG > 0V indicates current flow from WSe2 to the BTS electrode. Therefore, the direction of the built-in electric field is from WSe2 to the BTS, due to the transfer of interfacial electrons from WSe2 to the BTS when the two materials are in contact. For device 2, at VG < 0V, the photocurrent, built-in electric field direction, and interfacial electron transfer are from the BTS electrode to WSe2, opposite to those in device 1.

[0049] The calculation of the interface charge transfer combined with the work function shows that before contact, the Fermi level of the BTS in device 1 is located near the top of the valence band of WSe2, while that in device 2 is located near the bottom of the conduction band of WSe2, as shown in Figure 2. Figure 4 As shown in the left figure of a and 4b. Therefore, the BTS films of device 1 and device 2 are TaS2 terminated surface and Ba3TaS5 terminated surface respectively. The mechanism of photocurrent generation can be Figure 4c, where the left and right figures correspond to device 1 and device 2, respectively. In device 1, the N-type WSe2 band bending caused by the Schottky junction at the vdW contact separates the photogenerated carriers, causing electrons to move toward WSe2 and holes to move toward BTS. Figure 3 A negative photocurrent (Ids < 0) can be observed in the right image of d. For device 2, the band bending is exactly the opposite. Electrons move toward the BTS and holes move toward WSe2, resulting in a positive photocurrent (Ids > 0).

[0050] The electrical transport behavior can also be understood from the band arrangement. For the BTS with TaS2 termination (negative dipole, device 1), the high work function makes the BTS electrode behave as a p-type contact electrode material, such as Figure 4 As shown in a. At VG>0, the WSe2 channel is n-type, and the Schottky barrier between WSe2 and BTS is high (as shown in Figure 4 a right figure). The electrons from BTS are blocked by the Schottky barrier. Therefore, the electron transfer between BTS and WSe2 shows obvious rectification phenomenon. When VG<0( Figure 4 (middle image of a) When the WSe2 channel is set to p-type, the Schottky barrier becomes weaker. Therefore, the flow of holes has no direction selectivity. For the Ba3TaS5 terminated BTS, the low work function makes the BTS electrode behave as an n-type contact electrode material. Figure 4 As shown in b, the Schottky barrier is strong at VG < 0 and weak at VG > 0. Figure 2 As shown in Figures 2g and 2h, holes in the BTS are blocked by the Schottky barrier, while electrons are not, resulting in significant rectifying behavior when VG < 0. In general, the difference in work function between the two different termination surfaces leads to the rectifying mode and SPCM measurement results.

[0051] Therefore, surface dipoles make two-dimensional metallic vdWSL materials a novel class of materials for tunable Schottky contacts. First-principles calculations of BTS reveal that the interlayer dipoles are caused by charge transfer between TaS2 and Ba3TaS5 layers. When a BTS crystal is mechanically exfoliated, its superlattice structure allows the formation of two types of termination surfaces: TaS2 or Ba3TaS5. Consequently, TaS2- and Ba3TaS5-terminated BTSs exhibit negative and positive surface dipoles, as demonstrated by KPFM measurements. The switchable surface dipoles strongly modulate the work function of the BTSs, reaching 5.88 eV and 2.19 eV for TaS2- and Ba3TaS5-terminated BTSs, respectively. Due to the surface dipoles and van der Waals contacts, vdWSLs can be used to construct distinct two-dimensional Schottky diodes, as demonstrated in BTS / WSe2 vdW heterostructures. Due to the two surfaces of BTS and bipolar WSe2, all BTS / WSe2 devices can be divided into two categories based on the direction of rectification or contact type. BTS electrodes terminated with TaS2 / Ba3TaS5 can form P / N-type contacts with WSe2 due to their respective hole- and electron-injection capabilities. SPCM images reveal corresponding opposite photocurrents and opposite interfacial built-in electric fields at the Schottky contact interface, further confirming that the devices exhibit N / P-type Schottky junctions at + / -VG.

[0052] It is understood that the vdWSL material of the present invention is not limited to Ba6Ta. 11 S 28 (BTS), two-dimensional semiconductors are not limited to WSe2. Other two-dimensional metal vdWSLs can be (LaSe) 1.14 (NbSe2)2, (PbSe) 1.14 NbSe2, [(EuS) 1.5 ] 1.15 NbS2、Ba6Nb 11 S 28 Etc. Other two-dimensional semiconductors can be WS2, MoSe2, InSe, MoS2, MoTe2, etc.

[0053] See also Figures 5 to 8 , in (LaSe) 1.14 In the (NbSe2)2 crystal structure, LaSe layers and NbSe2 layers are alternately stacked in the c-axis direction. The LaSe layer is a barrier layer and the NbSe2 layer is a transition metal disulfide layer. The arrows indicate the direction of interlayer electron transfer, thereby forming an interlayer dipole. After mechanical peeling, a surface dipole can be generated. Similarly, in (PbSe) 1.14In NbSe2, PbSe layers and NbSe2 layers are stacked alternately in the c-axis direction. The PbSe layer is a barrier layer, and the NbSe2 layer is a transition metal disulfide layer. The arrows indicate the direction of interlayer electron transfer, thereby forming an interlayer dipole. After mechanical peeling, a surface dipole can be generated. In [(EuS) 1.5 ] 1.15 In the NbS2 crystal structure, EuS layers and NbS2 layers are alternately stacked in the c-axis direction, with the EuS layer being a barrier layer and the NbS2 layer being a transition metal disulfide layer. 11 S 28 In the crystal structure, Ba3NbS5 layers and NbS2 layers are stacked alternately in the c-axis direction, with the Ba3NbS5 layer serving as a barrier layer and the NbS2 layer serving as a transition metal disulfide layer.

[0054] It can be seen that the two-dimensional vdWSL with surface dipoles will become a new method for designing metal-semiconductor contacts. Due to the switchable nature of the surface dipole, vdWSL can achieve a wider range of work functions, making it a universal electrical contact material for constructing high-quality two-dimensional Schottky barriers. Compared with traditional electrode materials, vdWSL electrodes can obtain two types of contacts using one vdWSL crystal, and can even achieve electron or hole injection into the same semiconductor channel by changing its surface dipole. In addition to flexible design, suppression of metal-induced surface states and FLPE, vdWSL electrodes also bring new degrees of freedom. The surface dipole can be used to regulate the Schottky contact interface and increase the diversity of van der Waals contacts. This allows the development of more functional low-dimensional devices.

[0055] The method provided by the present invention for regulating metal-semiconductor contact using interlayer electric dipoles can switch the termination surface of the two-dimensional van der Waals superlattice metal material by mechanical peeling. The surface dipoles of different termination surfaces are inward or outward, and the switchable surface dipole has a strong modulation effect on the work function of the two-dimensional van der Waals superlattice metal material. The two-dimensional van der Waals superlattice metal material and the two-dimensional semiconductor form a Schottky junction, and the Schottky junction can produce two types of rectification effects. These behaviors can be attributed to the use of two-dimensional van der Waals superlattice metal material electrodes. When the surface of the two-dimensional van der Waals superlattice metal material is a sulfide barrier layer or a transition metal disulfide layer, two different surface dipoles can be obtained. Due to the presence of these two surface dipoles, the two-dimensional van der Waals superlattice metal material exhibits different work functions, thereby forming an N or P type contact with the two-dimensional semiconductor, realizing two rectification behaviors. In addition, the two Schottky junctions were studied using scanning photocurrent microscopy (SPCM), revealing the built-in electric field at the contact interface. The opposite photocurrent further verifies that the 2D van der Waals superlattice metal forms an N-type or P-type contact with the 2D semiconductor channel. This demonstrates that the surface dipoles of 2D van der Waals superlattice metals can be used to modulate the interfacial Schottky barrier at the metal-semiconductor contact. This advance also opens up new methods for designing and manipulating van der Waals contact interfaces using interlayer dipoles and the 2D van der Waals superlattice metal family, providing more freedom in device design and having practical applications in nanoelectronics and nanophotonics.

[0056] In addition, those skilled in the art may also make other changes within the spirit of the present invention. Of course, these changes made according to the spirit of the present invention should be included in the scope of protection required by the present invention.

Claims

1. A method for regulating metal-semiconductor contact using interlayer electric dipoles, comprising the following steps: Provide one- and two-dimensional van der Waals superlattice metal materials and two-dimensional semiconductors; Test the dipole direction on the surface of two-dimensional van der Waals superlattice metal materials; Switching the termination surface of the two-dimensional van der Waals superlattice metal material by mechanical exfoliation as needed; The required two-dimensional van der Waals superlattice metal material is brought into contact with a two-dimensional semiconductor, and the electric dipole between the two-dimensional van der Waals superlattice metal material and the two-dimensional semiconductor is used to regulate the metal-semiconductor contact.

2. The method for regulating metal-semiconductor contact using interlayer electric dipoles according to claim 1, wherein: The two-dimensional van der Waals superlattice metal material is formed by alternately stacking sulfide barrier layers and transition metal disulfide layers in the c-axis direction.

3. The method for regulating metal-semiconductor contact using interlayer electric dipoles according to claim 2, wherein: The termination surface of the two-dimensional van der Waals superlattice metal material is a sulfide barrier layer or a transition metal disulfide layer.

4. The method for regulating metal-semiconductor contact using interlayer electric dipoles according to claim 1, wherein: The step of testing the dipole direction of the two-dimensional van der Waals superlattice metal material surface includes: measuring the work function of the two-dimensional van der Waals superlattice metal material surface using a Kelvin probe microscope, and then inferring the direction of the dipole direction of the two-dimensional van der Waals superlattice metal material surface based on the work function.

5. The method for regulating metal-semiconductor contact using interlayer electric dipoles according to claim 1, wherein: By switching the termination surface of the two-dimensional van der Waals superlattice metal material through mechanical peeling, the direction of the dipole of the termination surface of the two-dimensional van der Waals superlattice metal material can be controlled.

6. The method for regulating metal-semiconductor contact using interlayer electric dipoles according to claim 1, wherein: The two-dimensional van der Waals superlattice metal material is Ba6Ta 11 S 28 、(LaSe) 1.14 (NbSe2)2, (PbSe) 1.14 NbSe2, [(EuS) 1.5 ] 1.15 NbS2 or Ba6Nb 11 S 28 .

7. The method for regulating metal-semiconductor contact using interlayer electric dipoles according to claim 1, wherein: The two-dimensional semiconductor is WSe2, WS2, MoSe2, InSe, MoS2 or MoTe2.

8. The method for regulating metal-semiconductor contact using interlayer electric dipoles according to claim 6, wherein: The two-dimensional van der Waals superlattice Ba6Ta 11 S 28 When the termination surface is TaS2 layer, the Ba6Ta 11 S 28 The surface dipoles are directed inwards.

9. The method for regulating metal-semiconductor contact using interlayer electric dipoles according to claim 6, wherein: The two-dimensional van der Waals superlattice Ba6Ta 11 S 28 When the termination surface is Ba3TaS5 layer, the Ba6Ta 11 S 28 The surface dipole is directed outwards.

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