Communication encryption method based on two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector

Abstract

The present invention discloses a method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector, which belongs to the technical field of optoelectronic devices. The photodetector includes a substrate, a two-dimensional MoSe2 material layer, a two-dimensional ReS2 material layer and a thin film electrode, and the two two-dimensional material layers constitute a van der Waals vertical heterojunction and a type II heterostructure; due to the anisotropic light absorption of ReS2, the effective carrier collection and transport capacity of MoSe2 and the inhibitory effect of the heterojunction on dark current, the photoelectric performance of the two-dimensional ReS2 / MoSe2 photodetector is significantly improved, and it also has a high responsivity of 89.4 A / W, a fast response speed of 30.5 µs and polarization sensitivity. On this basis, multiple encryption of information is performed with the help of polarization state information encryption technology, which can greatly improve the concealment and security of the information transmission process, and provide new possibilities for the development of future secure communication technology.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic devices, and in particular to a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector, a preparation method, and a method for performing communication encryption using the polarization photodetector. Background Art

[0002] With the development of nanotechnology, two-dimensional materials have become a type of material that technicians in this field have focused on studying because of their unique physical properties, such as strong photoluminescence (PL), strong light-matter coupling, and large electron effective mass. This type of material has become one of the important candidate materials for the preparation of photodetectors.

[0003] Compared with photodetectors made of single-layer two-dimensional materials, van der Waals heterojunction photodetectors are made of two or more different two-dimensional materials stacked by van der Waals forces to form a heterostructure. The design of the heterostructure can combine the advantages of each layer of materials, achieve complementary and enhanced performance, break the limitations of single-layer two-dimensional material photodetectors in specific performance, and improve the photoelectric performance of the photodetector.

[0004] However, even heterostructured photodetectors are mostly difficult to have both high responsiveness and fast response speed. This is mainly because some two-dimensional materials have defects such as large dark current, although they have high photoresponsivity, such as rhenium disulfide (ReS2). ReS2 is an n-type direct bandgap semiconductor, and its direct bandgap does not change with the number of layers. The presence of defect states in a few layers of ReS2 makes the ReS2 photocurrent produce a very high gain, and its photoresponsivity reaches 88600AW. -1 However, the deep bound state makes ReS2 have an ultra-long response time. Therefore, photodetectors based on ReS2 often cannot have both high responsiveness and fast response speed. In order to improve the performance of such devices, other two-dimensional materials selected to construct heterojunctions with ReS2 should be able to effectively suppress the influence of their defect states on the device.

[0005] Studies have shown that stacking ReS2 with other two-dimensional materials through van der Waals forces to form a type II band-aligned structure can enhance the effective separation and transmission of carriers, and also enable the heterojunction interface to have an enhanced interlayer coupling effect. For example, Chinese patent CN 110277461 B discloses an optoelectronic device based on a rhenium disulfide / tungsten diselenide heterojunction, which utilizes single-layer ReS2 and WSe2 to form a heterojunction. The n-type ReS2 and p-type WSe2 form a wide barrier region to suppress the influence of defect states in ReS2 on the detector, making the detector have fast responsiveness and breaking the performance limitations of ReS2 itself.

[0006] With the development of the digital age, while informatization has brought great convenience to daily life, the spread of information is also accompanied by serious information security issues. Information security has received more and more attention, and it is extremely necessary to develop new encrypted communication methods that can achieve advanced information encryption. Among them, polarization information is another important optical parameter independent of phase and amplitude. The encryption of polarization information has strong concealment, which fundamentally avoids illegal interception and tampering of information. Therefore, finding materials that have good optoelectronic properties and are sensitive to polarized light is crucial for the development of new detection and encryption technologies.

[0007] However, it can be seen from the relevant existing technologies that for heterojunction photodetectors based on ReS2, the main research direction of technical personnel in this field is still to explore new heterostructure building materials and preparation processes to improve the photoelectric performance of the device and suppress the influence of ReS2 defect states. There is a problem that the device function is relatively single, and it is difficult to use the same detector to achieve multiple functions, which does not meet the modern society's demand for multifunctional devices.

[0008] However, it is not easy to use two-dimensional materials to prepare multifunctional photodetectors. Since some two-dimensional materials do not have anisotropy, the multidimensional application of the corresponding materials is severely limited. Finding two-dimensional materials with high optoelectronic properties and anisotropy is a prerequisite for preparing multifunctional photodetectors. Studies have confirmed that the material ReS2 not only has a high photoresponsivity, but also because of its in-plane anisotropy, ReS2 has different responses to the polarization state of light, and it also has great application potential in the field of polarization detection. However, related research is not perfect, and the exploration of other functions of optoelectronic devices based on ReS2 is still in the initial development stage. It has not been successfully applied in the field of encrypted communications, and there is still a lot of room for research on related technologies.

[0009] In summary, if a heterostructured photodetector can be prepared based on ReS2, which has both high light responsiveness, fast response speed, and good polarization detection effect, and the corresponding photodetector can be successfully applied to the field of information encryption, it will not only expand the material library of high-performance photodetectors, but also provide new possibilities for the development of future secure communication technologies. Summary of the invention

[0010] The purpose of the present invention is to solve the problems existing in the prior art, provide a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector and disclose a specific preparation method, by constructing a van der Waals heterostructure and realizing van der Waals contact, the performance of the photodetector is effectively improved, and the resulting device has both high light responsiveness and fast light response rate. In addition, based on the in-plane structural anisotropy of ReS2 and its characteristics of different responses to the polarization state of light, the ReS2 / MoSe2 heterojunction has good polarization sensitivity. This type of heterostructure has broad application prospects in polarization imaging and encrypted communications.

[0011] In order to achieve the above technical objectives, the present invention is implemented through the following technical solutions: a method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector, the photodetector comprising a substrate and a two-dimensional MoSe2 material layer, a two-dimensional ReS2 material layer and a thin film electrode arranged in sequence on the substrate, the two two-dimensional material layers constitute a van der Waals vertical heterojunction and are a type II heterostructure, realizing van der Waals contact; when encrypting communication, it is necessary to preset the polarization angle corresponding to the current value of different colors, set the information to be transmitted, and preset the polarization angle; a beam of light passes through a polarizer at a predetermined polarization angle so that only light consistent with the polarization direction of the polarizer can pass through and irradiate the photodetector, thereby affecting the light signal received by the photodetector, and obtaining the photocurrent change at different polarization angles, which is used as the key of the photodetector, and the encrypted information is obtained by combining the pre-known characteristic sequence, Morse code and real color information.

[0012] Furthermore, the change of photocurrent at different polarization angles is achieved by setting a polarizer to control the polarization angle of incident light. Incident light at different polarization angles illuminates the photodetector to obtain the change of photocurrent at different polarization angles.

[0013] Furthermore, the specific operation process of encrypted communication is as follows:

[0014] 1) Use a signal generator or oscilloscope to control the light switch and the switching time to output the information to be transmitted, the on state is 1 and the off state is 0;

[0015] 2) Set the polarizer and use the photodetector to identify the transmitted signal: for the on state, the maximum current value obtained when the preset polarization angle is A corresponds to dark gray, the on state is 3, the minimum current value obtained when the polarization angle is B corresponds to light gray, the on state is 1, and the intermediate current value obtained when the polarization angle is C corresponds to gray and the on state is 2, where the intermediate current value is between the maximum current value and the minimum current value; set the off state to 0 and white to obtain the key;

[0016] 3) Combine the pre-known characteristic sequence to split the key information into breakpoints, and then decipher the specific letter information according to the Morse code;

[0017] 4) The corresponding current size corresponds to different polarization angles, and thus corresponds to the deciphered key images of different shades. The information conveyed by the letters corresponding to the image of the specified color is the real information.

[0018] Furthermore, in step 2), the polarization angle A is 90°, the polarization angle B is 0°, and the polarization angle C is 45°.

[0019] Furthermore, the two-dimensional MoSe2 material layer and the two-dimensional ReS2 material layer of the photodetector are transferred to the substrate by dry transfer, the thin film electrode is a gold electrode, and van der Waals metal contact is formed between the gold thin film and the two two-dimensional materials.

[0020] Furthermore, the photoresponsivity of the photodetector reaches 89.4 A / W, the rising and falling response times are 30.5 μs and 36.2 μs respectively, and the polarization sensitivity is 3.23.

[0021] The preparation steps of the above two-dimensional inorganic / inorganic van der Waals heterojunction photodetector are as follows:

[0022] 1) Pre-treating the substrate;

[0023] 2) The two-dimensional materials MoSe2 and ReS2 are peeled off on the blue film respectively, and pasted repeatedly to form MoSe2 / blue film and ReS2 / blue film structures;

[0024] 3) Laminating the PDMS film on a glass slide to obtain a PDMS / glass slide structure;

[0025] 4) Use mechanical peeling to transfer the two-dimensional materials MoSe2 and ReS2 to the PDMS film respectively to form a glass slide / PDMS / two-dimensional material structure, and cut off the excess PDMS film with the two-dimensional material to be transferred as the center;

[0026] 5) Fix the glass slide with the two-dimensional material MoSe2 in the substrate slot of the transfer table, and place the substrate on the sample holder of the transfer table;

[0027] 6) By controlling the bonding and separation rates of the transfer platform, the two-dimensional material MoSe2 is separated from PDMS and bonded to the substrate to obtain a MoSe2 / substrate structure;

[0028] 7) Fix the glass slide with the two-dimensional material ReS2 in the substrate slot of the transfer table, place the substrate on the sample holder of the transfer table, and align the ReS2 to be transferred with the MoSe2 part transferred to the substrate in the previous step;

[0029] 8) By controlling the bonding and separation rates of the transfer platform, the two-dimensional material ReS2 is separated from PDMS and bonded to the substrate to obtain a ReS2 / MoSe2 / substrate structure. The formed ReS2 / MoSe2 van der Waals vertical heterojunction is a type II heterostructure;

[0030] 9) Transfer the two prepared gold films to the two ends of one side of the ReS2 / MoSe2 van der Waals heterojunction built in the previous step to complete the preparation;

[0031] 10) Under an inert gas environment, place the photodetector in a tube furnace for annealing.

[0032] Furthermore, the surface of the PDMS film needs to be treated with UV-Ozone before transferring the two-dimensional material onto the PDMS film.

[0033] Furthermore, when transferring the two-dimensional material, the glass slide is lowered at a constant speed of 0.5~2 μm every 5 s so that the two-dimensional material is attached to the target substrate, and the attached state is maintained for 1~5 min. Thereafter, the glass slide is lifted up at a constant speed of 0.5~2 μm every 5 s so that the two-dimensional material is transferred to the surface of the target substrate.

[0034] Furthermore, in step 10), the annealing temperature is 150° C., the annealing time is 1 h, and the annealing process is carried out under nitrogen flow.

[0035] The beneficial effects of the present invention are:

[0036] 1. Due to the anisotropic light absorption of ReS2, the effective carrier collection and transport capacity of MoSe2, and the dark current suppression effect of the van der Waals heterojunction, the photoelectric performance of the two-dimensional ReS2 / MoSe2 photodetector prepared in this application is significantly improved. The prepared detector has both high responsiveness and fast response speed, breaking the application limitation of ReS2. Under 532 nm laser irradiation, it can achieve a current photoresponsivity of 89.4 A / W and a photoresponse speed of 30.5 µs. The comprehensive performance is better than most existing photoelectric devices, and it can achieve fast imaging, which has broad application prospects in the field of single-pixel imaging.

[0037] 2. Based on the in-plane structural anisotropy of ReS2 and its characteristics of different responses to the polarization state of light, the ReS2 / MoSe2 heterojunction prepared in this application has good polarization sensitivity, which makes this type of heterostructure have broad application prospects in the field of polarization photoelectric detection;

[0038] 3. This application combines the polarization-sensitive characteristics of ReS2 / MoSe2 photodetectors to propose a polarization state information encryption technology to perform multiple encryption of information. This technology converts the encrypted information into specific currents corresponding to different colors, and then restores it through a specially designed decryption algorithm, which greatly improves the concealment and security of the information transmission process and provides new possibilities for the development of future secure communication technology.

[0039] 4. This application constructs a two-dimensional ReS2 / MoSe2 photodetector device through mechanical stripping, dry transfer and transfer electrode method, ensuring the single crystallinity and purity of the material. Compared with the wet transfer process, the process is simple, the equipment requirements are low, the pollution is small, and there are no impurity molecules affecting the heterojunction contact, which facilitates the process-based preparation and saves production costs, making it likely to become a feasible choice for future low-cost and functional photodetection or neuromorphic applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a preparation flow chart of a two-dimensional inorganic / inorganic van der Waals heterojunction photodetector prepared in Example 1;

[0041] Figure 2 is an optical microscope photograph of the two-dimensional ReS2 / MoSe2 van der Waals heterojunction prepared in Example 1;

[0042] Figure 3 is an optical microscope photograph of the two-dimensional ReS2 / MoSe2 van der Waals heterojunction photodetector prepared in Example 1;

[0043] Figure 4 is a schematic structural diagram of a two-dimensional ReS2 / MoSe2 van der Waals heterojunction photodetector prepared in Example 1;

[0044] Figure 5 It is the Raman spectroscopy data of ReS2, MoSe2 and ReS2 / MoSe2 van der Waals heterojunction;

[0045] Figure 6 This is a photoresponsivity test diagram of the two-dimensional ReS2 / MoSe2 van der Waals heterojunction photodetector prepared in Example 1;

[0046] Figure 7 This is a response speed test diagram of the two-dimensional ReS2 / MoSe2 van der Waals heterojunction photodetector prepared in Example 1;

[0047] Figure 8 The photocurrent-polarization angle relationship and fitting curve of the two-dimensional ReS2 / MoSe2 van der Waals heterojunction photodetector prepared in Example 1;

[0048] Fig. 9A comparison chart of the photoresponsivity and polarization sensitivity of the two-dimensional ReS2 / MoSe2 van der Waals heterojunction photodetector prepared in Example 1 and other polarization photodetectors;

[0049] Fig.10 The international Morse code corresponding to the 26 English letters;

[0050] Fig.11 The figure is the false encrypted information detected by the photodetector prepared in Example 1 without adding a polarizing plate; sub-figure a is the modulation waveform emitted by the signal generator; sub-figure b is the current information obtained by the photodetector detecting the emitted signal without adding a polarizing plate; sub-figure c is the result of the photodetector identifying the emitted signal without adding a polarizing plate; sub-figure d is the image information obtained by breaking sub-figure c based on the digital sequence for decryption; sub-figure e is the information obtained by deciphering the international Morse code;

[0051] Fig.12 It is the real encrypted information detected by the photodetector prepared in Example 1 with the addition of a polarizing plate; sub-figure a is the current information obtained by the photodetector detecting the emitted signal with the addition of a polarizing plate; sub-figure b is the image information obtained by identifying the current information and according to the digital sequence and Morse code for decryption; sub-figure c is the correct information deciphered according to the international Morse code and color depth. DETAILED DESCRIPTION

[0052] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention.

[0053] Example 1

[0054] This embodiment discloses a method for preparing a two-dimensional inorganic / inorganic (ReS2 / MoSe2) van der Waals heterojunction photodetector based on a van der Waals contact interface. The preparation process is referred to Figure 1 , the specific preparation steps are as follows:

[0055] Step 1) Pre-treat the silicon (thickness 500 μm) / silicon oxide (thickness 275 nm) substrate (clean the surface with propanol after wafer cutting, then clean the surface propanol with deionized water, and blow dry the substrate with a nitrogen gun) to obtain a silicon-based substrate with a clean surface.

[0056] Step 2) The two-dimensional materials ReS2 and MoSe2 are peeled off on the blue film respectively, and pasted repeatedly to make the thickness reach about 20 nm, forming a two-dimensional material / blue film structure, namely ReS2 / blue film and MoSe2 / blue film.

[0057] Step 3) Cut the PDMS into small pieces of 0.5 cm*2 cm, peel off the protective film on its surface, and make it fit on the glass slide. Treat the PDMS surface with UV Ozone for 5 min, then repeatedly stick the two-dimensional material / blue film, transfer the ReS2 and MoSe2 on the blue film to the PDMS respectively, and find the few-layer, uniform, and wrinkle-free ReS2 and MoSe2 under the microscope (ReS2 has about 5 layers and a thickness of about 4 nm, and MoSe2 has about 8 layers and a thickness of about 6 nm), and use a blade to cut the PDMS film into 0.3 cm*0.3 cm squares with the transferred ReS2 / MoSe2 as the center (after cutting off the excess film, a certain width must be reserved between the material boundary and the film boundary, so that the two-dimensional material is as close as possible to the center of the cut film) to facilitate the subsequent transfer.

[0058] Step 4) On the transfer platform (its function is to find the MoSe2 observed under the microscope before and align it with the substrate to be transferred. The glass slide with the two-dimensional material is fixed in the substrate slot of the transfer platform, and the silicon-based substrate is adsorbed on the sample holder of the transfer platform. The transfer platform can be slowly raised and lowered. The minimum distance of the rise and fall is adjusted to 0.5 μm, so that the two-dimensional material can be slowly bonded to the substrate surface). First, find the MoSe2 to be transferred and align it with the substrate structure to be transferred. During the transfer process, the bonding process is kept at a uniform speed, descending 0.5 μm every 5 s. After complete bonding, keep bonding for 1 min, and then separate them at a uniform speed of 0.5 μm every 5 s (avoid rapid separation so that the material is torn or leave a large number of bubbles and residual glue), and obtain the MoSe2 / substrate structure.

[0059] Step 5) On the same transfer platform (its function is to find the ReS2 observed under the microscope before, the glass slide with the two-dimensional material ReS2 is fixed in the substrate slot of the transfer platform, the silicon-based substrate is adsorbed on the sample holder of the transfer platform, and the transfer platform can be slowly raised and lowered. The minimum distance of the rise and fall is adjusted to 0.5μm, so that the two-dimensional material can be slowly bonded to the substrate surface), first find the ReS2 to be transferred, and align it with the MoSe2 part transferred to the silicon substrate in the previous step. During the transfer process, the bonding process is kept at a uniform speed, descending 0.5μm every 5s. After complete bonding, keep bonding for 1 min, and then separate them at a uniform speed of 0.5μm every 5s (avoid rapid separation that causes the material to be torn or leaves a large number of bubbles and residual glue), and obtain the ReS2 / MoSe2 / substrate structure. The optical microscope photo of the ReS2 / MoSe2 van der Waals heterojunction is shown in the figure. Figure 2 shown.

[0060] Step 6) Attach a 200-mesh copper mesh to the silicon wafer and place it in a high vacuum electron beam evaporation coating apparatus to evaporate 120 nm thick gold. Remove the copper mesh and use a fine needle with a needle tip diameter of 1 μm to cut the gold film into 600 μm × 70 μm strip films.

[0061] Step 7) On the constructed ReS2 / MoSe2 van der Waals heterojunction, use a fine needle with a tip diameter of 15 μm to transfer the strip-shaped gold film prepared in the previous step to the two ends of one side of the heterojunction. The distance between the two transferred strip-shaped gold films is 5 μm.

[0062] Step 8) Place the prepared van der Waals heterojunction photodetector into a tube furnace and anneal at 150° C. for 1 hour, with nitrogen gas flowing throughout the process.

[0063] Figure 3 is an optical microscope photograph of the photodetector device prepared in this embodiment. The ReS2 layer and the MoSe2 layer form van der Waals contact to obtain a ReS2 / MoSe2 heterojunction. Compared with a single two-dimensional material, the light absorption is enhanced, which helps to improve the photoresponsivity of the material; and the construction of the van der Waals heterostructure will form a built-in electric field, which effectively promotes the separation of carriers, and also helps to improve the photoresponse speed of the device.

[0064] The structure of the device is as follows: Figure 4 As shown, a two-dimensional MoSe2 material layer, a two-dimensional ReS2 material layer and a gold film are sequentially arranged on a substrate; the two-dimensional MoSe2 material layer and the two-dimensional ReS2 material layer are transferred to the substrate by dry transfer, and the two two-dimensional material layers constitute a van der Waals vertical heterojunction and a type II heterostructure, realizing van der Waals contact; van der Waals metal contact is formed between the gold film and the two two-dimensional materials, and no doping is produced on the two-dimensional materials, solving the problem that the electron beam evaporation electrode will destroy and dope the two-dimensional materials. While having good contact, the heterojunction properties will not be changed; and the contact resistance can be reduced, and the Fermi level pinning effect at the metal-semiconductor interface can be reduced, which is helpful to improve the detector performance.

[0065] Figure 5 These are the Raman spectra of ReS2, MoSe2 and ReS2 / MoSe2 van der Waals heterojunction. From the figure, the Raman peak positions of single two-dimensional materials and stacked heterostructures can correspond one to one, indicating the successful construction of the heterostructure.

[0066] Figure 6 It shows that the photoresponsivity of the prepared photodetector can reach up to 89.4 A / W, which is a high photoresponsivity.

[0067] Figure 7This is a fitting result diagram of the light response speed of the two-dimensional inorganic / inorganic heterovan der Waals junction photodetector prepared in this embodiment. The increased current after illumination is mainly contributed by photogenerated carriers. At this time, the measured rise and fall response times are 30.5 μs and 36.2 μs respectively, and the response speed is very fast.

[0068] Figure 8 The photocurrent-polarization angle relationship and fitting curve of the two-dimensional inorganic / inorganic heterovan der Waals junction photodetector prepared in this embodiment show that the polarization sensitivity I max / I min =3.23.

[0069] Comparing the differences in light responsivity and polarization sensitivity between the photodetector prepared in this embodiment and other polarization photodetectors, the results are as follows: Fig. 9 As shown in the figure, it can be seen that the optoelectronic device prepared in this embodiment has both high light response and polarization sensitivity, and has excellent comprehensive performance.

[0070] Application Examples

[0071] Based on the characteristics of the photodetector prepared in Example 1, which has high light responsivity and high polarization sensitivity, this application example uses it in encrypted communication. Specifically, Fig.11 As shown in Figure a, the switch and switch time of the light are controlled by a signal generator or an oscilloscope to output the information to be transmitted, the on state displays 1, and the off state displays 0. Without adding a polarizing plate, the photodetector prepared in Example 1 recognizes the signal emitted by the signal generator ( Fig.11 Neutron Figure b), the on state is gray (1), the off state is white (0), and we get Fig.11 Neutron diagram c shows the coded information. Since Morse code itself has no particularly obvious rules, we get Fig.11 After reading the cipher information shown in the neutron diagram c, the specific information cannot be deciphered. This requires knowing a sequence of numbers for decryption in advance, such as: 945578665. Each number corresponds to Fig.11 The sub-image c of represents the number of frames to be extracted. For example, the first number 9 represents the first nine frame images to be selected, and the images are divided in sequence to obtain Fig.11 The result is shown in the neutron diagram d. Fig.10 The corresponding international Morse code image is translated into Fig.11 The results shown in Figure e are displayed as "PASSWORDS".

[0072] However, the information "PASSWORDS" obtained by the above method is the result without polarization, which is actually false information. The real information can only be obtained by adding a polarizer during detection. A beam of light passes through the polarizer at a predetermined polarization angle so that only light with the same polarization direction as the polarizer can pass through and illuminate the photodetector, and obtain the photocurrent changes at different polarization angles. Figure 8 The displayed polarization information, for the on state (gray), sets the maximum current value when the polarization angle is 90°, corresponding to dark gray, and the on state is 3; the minimum current value is obtained when the polarization angle is 0°, corresponding to light gray, and the on state is 1; the intermediate current value (between the maximum current value and the minimum current value) is obtained when the polarization angle is 45°, corresponding to gray (the grayscale of the gray is between dark gray and light gray), and the on state is 2; the off state corresponds to white (the off state is 0). The corresponding current size corresponds to different polarization angles, and thus corresponds to the deciphered key images of different shades. The information transmitted by the letters corresponding to the deciphered darkest or lightest image is set as the real information. The complete result after deciphering is as follows Fig.12 As shown in neutron image b, a total of nine letters were deciphered. The information was distinguished by color. The 1st, 2nd, 4th, and 9th deciphered letters in dark gray were selected to form "PASS", the 3rd deciphered letter in light gray was selected to form "S", and the 5th, 6th, 7th, and 8th deciphered letters in gray were selected to form "WORD". The final result is as follows: Fig.12 As shown in neutron image c, the darkest "PASS" or the lightest "S" represents true information.

[0073] In this application example, the encrypted information is converted into specific currents corresponding to different colors, and then restored through a specific decryption method, which can greatly improve the concealment of the information transmission process and enhance communication security.

[0074] The above shows and describes the basic principles, main features and advantages of the present invention. However, the above is only a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation methods derived by any technician in the field without departing from the technical solution of the present invention should be included in the patent scope of the present invention.

Claims

1. A method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector, characterized in that: The photodetector comprises a substrate and a two-dimensional MoSe2 material layer, a two-dimensional ReS2 material layer and a thin film electrode arranged in sequence on the substrate, wherein the two two-dimensional material layers constitute a van der Waals vertical heterojunction and are a type II heterostructure; When encrypting communications, preset the identification colors corresponding to the current values ​​obtained at different polarization angles; Then set the information to be transmitted and preset the polarization angle; A beam of light is passed through a polarizer at a predetermined polarization angle so that only light that is consistent with the polarization direction of the polarizer can pass through and illuminate the photodetector, thereby affecting the light signal received by the photodetector, and obtaining the photocurrent changes at different polarization angles. This is used as the key of the photodetector, and the encrypted information is obtained by combining the pre-known characteristic sequence, Morse code, and real color information.

2. The method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector according to claim 1, characterized in that: The change of photocurrent under different polarization angles is achieved by setting a polarizer to control the polarization angle of the incident light. Incident light with different polarization angles illuminates the photodetector to obtain the change of photocurrent under different polarization angles.

3. The method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector as claimed in claim 1, characterized in that: The specific operation process is as follows: 1) Use a signal generator or oscilloscope to control the light switch and the switching time to output the information to be transmitted, the on state is 1 and the off state is 0; 2) Set the polarizer and use the photodetector to identify the transmitted signal: for the on state, the maximum current value obtained when the preset polarization angle is A corresponds to dark gray, the on state is 3, the minimum current value obtained when the polarization angle is B corresponds to light gray, the on state is 1, and the intermediate current value obtained when the polarization angle is C corresponds to gray and the on state is 2, where the intermediate current value is between the maximum current value and the minimum current value; set the off state to 0 and white to obtain the key; 3) Combine the pre-known characteristic sequence to split the key information into breakpoints, and then decipher the specific letter information according to the Morse code; 4) The corresponding current size corresponds to different polarization angles, and thus corresponds to the deciphered key images of different shades. The information conveyed by the letters corresponding to the image of the specified color is the real information.

4. The method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector as claimed in claim 3, characterized in that: In step 2), the polarization angle A is 90°, the polarization angle B is 0°, and the polarization angle C is 45°.

5. The method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector according to claim 1, characterized in that: The two-dimensional MoSe2 material layer and the two-dimensional ReS2 material layer are transferred to the substrate by dry transfer. The thin film electrode is a gold electrode, and van der Waals metal contact is formed between the gold thin film and the two two-dimensional materials.

6. The method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector according to claim 1, characterized in that: The photoresponsivity of the photodetector reaches 89.4 A / W, the rising and falling response times are 30.5 μs and 36.2 μs respectively, and the polarization sensitivity is 3.

23.

7. The method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector according to claim 1, characterized in that: The preparation steps of the two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector are as follows: 1) Pre-treating the substrate; 2) The two-dimensional materials MoSe2 and ReS2 are peeled off on the blue film respectively, and pasted repeatedly to form MoSe2 / blue film and ReS2 / blue film structures; 3) Laminating the PDMS film on a glass slide to obtain a PDMS / glass slide structure; 4) Use mechanical peeling to transfer the two-dimensional materials MoSe2 and ReS2 to the PDMS film respectively to form a glass slide / PDMS / two-dimensional material structure, and cut off the excess PDMS film with the two-dimensional material to be transferred as the center; 5) Fix the glass slide with the two-dimensional material MoSe2 in the substrate slot of the transfer table, and place the substrate on the sample holder of the transfer table; 6) By controlling the bonding and separation rates of the transfer platform, the two-dimensional material MoSe2 is separated from PDMS and bonded to the substrate to obtain a MoSe2 / substrate structure; 7) Fix the glass slide with the two-dimensional material ReS2 in the substrate slot of the transfer table, place the substrate on the sample holder of the transfer table, and align the ReS2 to be transferred with the MoSe2 part transferred to the substrate in the previous step; 8) By controlling the bonding and separation rates of the transfer platform, the two-dimensional material ReS2 is separated from PDMS and bonded to the substrate to obtain a ReS2 / MoSe2 / substrate structure. The formed ReS2 / MoSe2 van der Waals vertical heterojunction is a type II heterostructure; 9) Transfer the two prepared gold films to the two ends of one side of the ReS2 / MoSe2 van der Waals heterojunction built in the previous step to complete the preparation; 10) Under an inert gas environment, place the photodetector in a tube furnace for annealing.

8. The method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector as claimed in claim 7, characterized in that: Before transferring the two-dimensional material onto the PDMS film, the surface of the PDMS film needs to be treated with UV-Ozone.

9. The method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector according to claim 7, characterized in that: When transferring two-dimensional materials, the slide is lowered at a constant speed of 0.5~2 μm every 5 s to allow the two-dimensional material to adhere to the target substrate. The adhered state is maintained for 1~5 min, and then the slide is lifted at a constant speed of 0.5~2 μm every 5 s to transfer the two-dimensional material to the surface of the target substrate.

10. The method for communication encryption based on a two-dimensional inorganic / inorganic van der Waals heterojunction polarization photodetector according to claim 7, characterized in that: In step 10), the annealing temperature is 150° C., the annealing time is 1 h, and the annealing process is carried out under nitrogen flow.

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