Preparation method and application of wafer-level palladium ditelluride-palladium diselenide vertical heterojunction thin film for nonlinear saturable absorber

Abstract

The invention discloses a preparation method and application of a wafer-level palladium ditelluride-palladium diselenide vertical heterojunction thin film for a nonlinear saturable absorber. The structure of the material sequentially comprises a palladium ditelluride thin film and a palladium diselenide thin film from top to bottom, and the wafer-level two-dimensional palladium ditelluride-palladium diselenide thin film vertical heterojunction is prepared by adopting a chemical vapor deposition technology assisted by electron beam evaporation coating. Experimental results show that the nonlinear absorption performance of the obtained heterojunction thin film is superior to that of a single palladium ditelluride thin film in a visible wave band of 550 nm; in the near-infrared band of 1550 nm, the modulation depth can reach 31.92%, and the wide-spectrum response characteristic from the visible band to the near-infrared band is shown. The material obtained by the invention has the advantages of controllable wafer-level growth, excellent nonlinear performance, wide operating wavelength range and the like, provides important material strategy and theoretical support for the design of ultrafast photonic devices such as high-performance mode-locked lasers and all-optical switches, and has important application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of two-dimensional materials and nonlinear optics, and particularly relates to a preparation method of a wafer-level two-dimensional palladium ditelluride-palladium diselenide vertical heterojunction film for a nonlinear saturable absorber and application thereof. BACKGROUND

[0002] In the field of nonlinear optics, saturable absorption materials have become key materials for regulating optical signals and realizing optical pulse compression and stability control due to their light intensity-dependent absorption characteristics, i.e., strong absorption under weak light and saturated absorption under strong light. At present, semiconductor saturable absorber mirrors (SESAMs) are the most widely used technical solution in commercial applications, but they still have obvious shortcomings, mainly including high cost, complex preparation process and narrow working wavelength range, which is difficult to cover the wide spectrum from visible to near-infrared.

[0003] In recent years, two-dimensional materials are considered as ideal candidate materials for a new generation of saturable absorbers due to their unique energy band structure and excellent photoelectric properties. Among many two-dimensional materials, palladium diselenide, as one of the typical transition metal chalcogenides, has high carrier mobility and a thickness-dependent band gap (from 1.3 eV for a single layer to 0.03 eV for a bulk material), and exhibits good saturable absorption behavior in the visible light band, attracting extensive research by researchers. However, due to its inherent energy band structure, few-layer palladium diselenide has a limited absorption range and only exhibits effective saturable absorption characteristics in the visible light band (400-700 nm), making it difficult to effectively expand to the near-infrared region. Unlike graphene I-type semimetals with symmetric energy band structures, palladium ditelluride is a II-type Dirac semimetal with a highly tilted Dirac cone structure and super-wide spectrum absorption capability (ultraviolet to terahertz band), high carrier mobility, but its modulation depth is low, limiting its separate application in ultrafast optical devices.

[0004] Therefore, how to combine the strong visible light absorption of palladium diselenide with the wide spectrum characteristics of palladium ditelluride to construct a heterojunction with enhanced nonlinear response and wide band working capability has become a research hotspot in this field. In particular, it is still a technical problem to be solved to realize wafer-level, controllable and catalyst-free synthesis of such a heterojunction to meet the large-scale preparation needs of future optoelectronic integrated devices.

[0005] Based on this, the application proposes a preparation method based on electron beam evaporation assisted chemical vapor deposition, which successfully constructs a palladium ditelluride-palladium diselenide vertical heterojunction film on a wafer-level substrate, not only overcoming the performance limitations of a single material, but also realizing high modulation depth and excellent nonlinear response from visible to near-infrared bands, providing a material basis for the engineering application of developing new ultrafast photonic devices (such as all-optical switches and mode-locked lasers). SUMMARY

[0006] In view of the above technical problems of the prior art, the present application provides a preparation method of wafer-level palladium ditelluride-palladium diselenide vertical heterojunction film for nonlinear saturable absorber and application thereof, which realizes the preparation of wafer-level palladium ditelluride-palladium diselenide vertical heterojunction film by adopting electron beam evaporation coating assisted chemical vapor deposition technology. The obtained wafer-level heterojunction film is proved to have significantly enhanced nonlinear optical response, which lays an important material foundation for developing new ultrafast photonic devices such as wide-spectrum mode-locked laser, tunable optical switch and the like.

[0007] To achieve the above-mentioned purpose, the present application realizes the following scheme:

[0008] A preparation method of wafer-level palladium ditelluride-palladium diselenide vertical heterojunction film for nonlinear saturable absorber, comprising the following steps:

[0009] S1. A blank substrate is pretreated to remove surface impurities and contaminants;

[0010] S2. An electron beam evaporation coating instrument is used to deposit a palladium thin film on the pretreated substrate obtained in step S1, the evaporation rate is controlled at 1.0-1.5 Å / s, and the deposition time is 25-30 min, to obtain a substrate with a palladium pre-deposition layer;

[0011] S3. The substrate with the palladium pre-deposition layer obtained in step S2 is placed in the central heating area of a tube furnace, and a quartz boat containing selenium powder is placed 2-6 cm upstream from the heating center. Before heating reaction, pure argon gas is introduced into the tube furnace for 10-50 minutes to evacuate the tube, then the vacuum pump is started to draw the system pressure to a low pressure environment of -10 Pa to -8 MPa, argon gas with a flow rate of 150-300 sccm is used as carrier gas, the furnace temperature is raised to 260-330 ℃, and the temperature is kept for 60-80 min for selenium reaction. After the reaction is completed, the system is naturally cooled to room temperature to obtain a palladium diselenide film;

[0012] S4. The palladium diselenide film obtained in step S3 is used as a substrate, and a palladium thin film is pre-deposited again by electron beam evaporation, and the parameters are the same as those in step S2;

[0013] S5. The thin film of secondary deposited palladium obtained in step S4 is placed in the second temperature zone heating center of the double temperature zone tube furnace, and a quartz boat containing tellurium powder is placed in the first temperature zone heating center of the double temperature zone tube furnace; before growth, the reaction cavity is cleaned for 1-5 minutes using argon-hydrogen mixed gas, and then under atmospheric pressure, argon gas with a flow rate of 10-30 sccm is used as the carrier gas, the first temperature zone is raised to 450-650 ℃, the second temperature zone is raised to 250-450 ℃, and the tellurization reaction is carried out for 8-180 min, and after the reaction is completed, the temperature is naturally cooled to room temperature, thereby obtaining a wafer-level palladium ditelluride-palladium diselenide vertical heterojunction thin film.

[0014] Further, in step S1, the substrate comprises any one of silicon, silicon oxide, sapphire or soda-lime glass.

[0015] Further, in step S1, the substrate has a size of 1-3 inch wafer and a thickness of 0.05-1.1 centimeters, preferably a 2 inch soda-lime glass wafer substrate with a thickness of 0.7 centimeters, which can be directly used for subsequent nonlinear optical tests after growing samples on the surface thereof.

[0016] Further, in step S2, the thickness of the palladium thin film is 1-10 nanometers, which can be selected according to actual needs.

[0017] Further, in step S3, the selenium powder is high-purity selenium powder with a purity of 99.9%.

[0018] Further, in step S3, the flow rate of the pure argon gas used for evacuation is 150-500 sccm.

[0019] Further, in step S3, the selenization reaction temperature is preferably 300-325 ℃, and the selenization time is preferably 60-70 min.

[0020] Further, in step S5, the tellurium powder is high-purity tellurium powder with a purity of 99.9%.

[0021] Further, in step S5, the flow rate of argon in the argon-hydrogen mixed gas is 460-520 sccm, and the flow rate of hydrogen is 460-520 sccm.

[0022] Further, in step S5, the first temperature zone heating temperature is preferably 450-500 ℃, the second temperature heating temperature is preferably 250-300 ℃, and the tellurization time is preferably 10-20 min.

[0023] The wafer-level palladium ditelluride-palladium diselenide vertical heterojunction thin film obtained by the above preparation method is used for preparing a nonlinear optical device, and has excellent performance.

[0024] Compared with the prior art, the present application has obvious advantages and beneficial effects, specifically, from the above technical solution, it can be known that:

[0025] (1) The present application combines electron beam evaporation coating and chemical vapor deposition technology to realize controllable preparation of wafer-level two-dimensional palladium ditelluride-palladium diselenide vertical heterojunction film. This method not only has simple process and low cost, but also has good repeatability and uniformity, and is suitable for large-area and large-scale production.

[0026] (2) The prepared wafer-level heterojunction film successfully solves the problem of large-scale application of two-dimensional materials in integrated devices, provides a reliable material platform for their practical application in ultrafast photonic devices, and has strong industrialization prospects.

[0027] (3) The generated heterojunction film can be directly used for nonlinear performance testing by using sodium-calcium glass as a substrate, avoiding the complicated substrate transfer process, thereby reducing the risk of damage to the integrity of the film, and ensuring the reliability and accuracy of the test results.

[0028] (4) In the entire preparation process, no catalyst (such as chloride, hydroxide, etc.) is introduced, only high-purity (99.9%) selenium powder and tellurium powder are used as precursors, thereby effectively avoiding impurity pollution, ensuring the cleanliness of the heterojunction interface and the high purity of the material.

[0029] In summary, the wafer-level two-dimensional palladium ditelluride-palladium diselenide vertical heterojunction film prepared by the present application has excellent nonlinear optical performance. Specifically, in the 550 nm visible band, the saturation absorption characteristics of the two-dimensional palladium ditelluride-palladium diselenide heterostructure are significantly stronger than those of pure materials, wherein compared with pure two-dimensional palladium ditelluride, the nonlinear absorption coefficient of the heterostructure is increased by 48%, the modulation depth is increased by 58%, and the saturation light intensity is reduced by 22%; in the 1550 nm near-infrared band, the modulation depth reaches 31.92%, showing a wide spectral response characteristic from visible to near-infrared band. This material has important application value in mode-locked laser, all-optical switch, optical communication and other ultrafast photonic devices. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Digital photo of wafer-level two-dimensional palladium ditelluride-palladium diselenide vertical heterojunction film prepared by electron beam evaporation assisted chemical vapor deposition method and original sodium-calcium glass substrate;

[0031] Figure 2 Raman spectrum characterization results of wafer-level two-dimensional palladium ditelluride-palladium diselenide vertical heterojunction film prepared by electron beam evaporation assisted chemical vapor deposition method;

[0032] Figure 3Raman spectroscopy mapping images of wafer-scale PdTe2-PdSe2 vertical heterojunction thin films prepared by electron-beam evaporation assisted chemical vapor deposition, where (a) corresponds to E g vibrational mode characterization results, the lower left corner inset is the corresponding optical microscope image, (b) corresponds to A g 1 -B g 1 vibrational mode characterization results, (c) corresponds to A g 3 vibrational mode characterization results;

[0033] Figure 4 Atomic force microscopy characterization results of wafer-scale PdTe2-PdSe2 vertical heterojunction thin films prepared by electron-beam evaporation assisted chemical vapor deposition;

[0034] Figure 5 X-ray photoelectron spectroscopy images of wafer-scale PdTe2-PdSe2 vertical heterojunction thin films prepared by electron-beam evaporation assisted chemical vapor deposition, where (a) is the full spectrum characterization result image, (b) is the Pd 3d orbital characterization result image, (c) is the Te 3d orbital characterization result image, and (d) is the Se 3d orbital characterization result image;

[0035] Figure 6 Ultraviolet-visible-infrared absorption spectroscopy characterization results of PdTe2-PdSe2 heterojunction, pure PdTe2, and pure PdSe2;

[0036] Figure 7 Open aperture Z-scan test results of PdTe2-PdSe2 heterojunction, pure PdSe2, and pure PdTe2 samples, where the light excitation wavelength used for testing is 550 nm, and the incident light intensity is 27.8 GW / cm 2 ;

[0037] Figure 8 Nonlinear optical parameter statistical diagrams of PdTe2-PdSe2 heterojunction and pure PdTe2 samples under light excitation wavelength of 550 nm and incident pulse intensity of 27.8 GW / cm 2 , where (a) is the nonlinear absorption coefficient β statistical diagram of the two samples, (b) is the modulation depth α s and saturation light intensity I sat statistical diagram of the two samples;

[0038] Figure 9The open aperture Z-scan test results of the PdTe2-PdSe2 heterojunction, pure PdSe2 and pure PdTe2 samples under the light excitation wavelengths of 1100 nm and 1550 nm, wherein (a) is the test result graph of the PdTe2-PdSe2 heterojunction under different incident light intensities at the light excitation wavelength of 1100 nm, (b) is the test result graph of the PdTe2-PdSe2 heterojunction under different incident light intensities at the light excitation wavelength of 1550 nm, (c) is the test result graph of pure PdSe2 and pure PdTe2 under the light excitation wavelength of 1100 nm and the incident light intensity of 27.8 GW / cm 2 , (d) is the test result graph of pure PdSe2 and pure PdTe2 under the light excitation wavelength of 1550 nm and the incident light intensity of 27.8 GW / cm 2 ;

[0039] Figure 10 The nonlinear optical parameter statistical graph of the PdTe2-PdSe2 heterojunction under the light excitation wavelengths of 1100 nm and 1550 nm and the incident light intensity of 27.8 GW / cm 2 , wherein (a) is the nonlinear absorption coefficient β statistical graph under different light excitation wavelengths, (b) is the modulation depth α s and the saturation light intensity I sat statistical graph under different light excitation wavelengths;

[0040] Figure 11 The experimental result graph of Example 2, (a) the optical microscope image of the PdTe2-PdSe2 vertical heterojunction thin film grown on a silicon oxide substrate, (b) the Raman spectrum characterization result, (c) the open aperture Z-scan test result curve under the light excitation wavelength of 1550 nm, (d) the relationship between the nonlinear transmittance and the incident light intensity;

[0041] Figure 12 The experimental result graph of Example 3, (a) the optical microscope image of the PdTe2-PdSe2 vertical heterojunction thin film grown on a sapphire substrate, (b) the Raman spectrum characterization result, (c) the open aperture Z-scan test result curve under the light excitation wavelength of 1550 nm, (d) the relationship between the nonlinear transmittance and the incident light intensity;

[0042] Figure 13 The Raman spectrum characterization result graph of Comparative Example 1;

[0043] Figure 14 The Raman spectrum characterization result graph of Comparative Example 2. DETAILED DESCRIPTION

[0044] The application will be further described in detail below with reference to the accompanying drawings.

[0045] Example 1

[0046] A soda lime glass substrate with a thickness of 0.7 cm and a size of 2 inches was first cleaned by ultrasonic cleaning in deionized water, acetone and ethanol for 20 minutes and dried in a nitrogen stream to obtain a clean substrate. Then, a 1 nm metal palladium film was deposited on the substrate by electron beam evaporation technology at a fixed evaporation rate of 1.0 Å / s to obtain a pre-deposited soda lime glass substrate. The substrate with the deposited palladium film was placed in the heating center of a tube furnace, and a quartz boat loaded with a selenium powder precursor with a mass of 200 mg and a purity of 99.9% was placed 4 cm upstream of the heating center. Before heating the reaction, pure argon was introduced into the tube furnace for 30 min to remove the residual air in the tube. Then, the system pressure was pumped to a low pressure environment of ~10 Pa by starting the vacuum pump, and the furnace temperature was raised to 325 ℃ within 30 min using 200 sccm Ar as the carrier gas. The seleniumization reaction was carried out at this temperature for 60 min, and the palladium diselenide film was prepared after natural cooling to room temperature. The prepared palladium diselenide film was used as a substrate, and a 1 nm metal palladium film was again pre-deposited by electron beam evaporation method under the same parameter conditions to obtain a second pre-deposited substrate, which was placed in the second heating center of a double-zone tube furnace, and a quartz boat loaded with a tellurium powder precursor with a mass of 50 mg and a purity of 99.9% was placed in the first heating center. Before growth, the reaction chamber was cleaned with argon-hydrogen mixed gas. Then, under atmospheric pressure, the temperature of the first heating zone was raised to 450 ℃ and the temperature of the second heating zone was raised to 300 ℃ within 16 min using 20 sccm Ar as the carrier gas, and the tellurization reaction was carried out for 10 min. The final palladium ditelluride-palladium diselenide heterojunction film was formed on the surface of the 2-inch soda lime glass wafer substrate after natural cooling to room temperature.

[0047] The obtained wafer-level palladium ditelluride-palladium diselenide heterojunction film was uniform in surface, as shown in FIG. 1. Figure 1 The palladium ditelluride-palladium diselenide heterojunction film sample grown on the surface of the 2-inch soda lime glass wafer substrate in this example was characterized by Raman spectroscopy, Raman spectroscopy area scanning, atomic force microscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible-near infrared absorption spectroscopy, and the results are shown in FIG. 2. Figures 2-6 From the Raman spectroscopy characterization results, it can be seen that there are obvious characteristic peaks at ~78 cm -1 , ~144 cm -1 and ~259 cm -1 , which are respectively the E g vibration mode of pure palladium ditelluride and the A g 1 -B g 1 , A g 3The vibration modes correspond to the reported results, indicating that the PdTe2-PdSe2 heterojunction film is successfully synthesized. The Raman spectral mapping image shows the E g The vibration modes correspond to the reported results, indicating that the PdTe2-PdSe2 heterojunction film is successfully synthesized. The Raman spectral mapping image shows the E g 1 The vibration modes correspond to the reported results, indicating that the PdTe2-PdSe2 heterojunction film is successfully synthesized. The Raman spectral mapping image shows the E g 1 The vibration modes correspond to the reported results, indicating that the PdTe2-PdSe2 heterojunction film is successfully synthesized. The Raman spectral mapping image shows the E g 3 The vibration modes correspond to the reported results, indicating that the PdTe2-PdSe2 heterojunction film is successfully synthesized. The Raman spectral mapping image shows the E Figure 3 (a) are the corresponding optical microscope images. The three characteristic Raman peaks show a highly uniform spatial distribution in the scanning area, confirming the uniformity of the prepared PdTe2-PdSe2 heterostructure. The PdTe2-PdSe2 The atomic force microscope image of the PdTe2-PdSe2 vertical heterojunction film shows that the average thickness of the prepared film is about 35.5 nm. According to the fitting results of the X-ray photoelectron spectroscopy, the full spectrum clearly shows the Pd characteristic peaks existing in both materials, the Te characteristic peaks from pure PdTe2 and the Se characteristic peaks from pure PdSe2. Among them, there are two peaks at 336.4 eV and 341.6 eV in the Pd 3d orbital fitting curve, four peaks at 573.3 eV, 576.6 eV, 583.7 eV and 587.0 eV in the Te 3d orbital fitting curve, and two peaks at 54.7 eV and 55.6 eV in the Se 3d orbital fitting curve, which are consistent with the reported standard orbital fitting curves. According to the characterization results of the ultraviolet-visible-near infrared absorption spectrum, the synthesized PdTe2-PdSe2 heterojunction film exhibits a flat absorption curve in the ultraviolet-near infrared band, which is beneficial to broadband optical applications. Especially in the near infrared band with a wavelength greater than 800 nm, the absorbance is significantly higher than that of PdTe2 and PdSe2 pure materials, which reflects excellent absorption characteristics.

[0048] Subsequently, the PdTe2-PdSe2 heterojunction, pure PdSe2, and pure PdTe2 samples were subjected to open-aperture Z-scan tests. As Figure 7 shown, when the light excitation wavelength is 550 nm and the incident pulse intensity is 27.8 GW / cm 2 Next, the constructed PdTe2-PdSe2 heterojunction improves the saturated absorption characteristics of the pure material; as Figure 8 shown, the nonlinear absorption coefficient and modulation depth of the PdTe2-PdSe2 heterojunction are improved by 48% and 58% compared with PdTe2, respectively, while the saturation light intensity is reduced by 22%. In order to further explore the nonlinear optical properties of the sample in the near-infrared band, the sample was subjected to open-aperture Z-scan tests at wavelengths of 1100 nm and 1550 nm, and the test results are as Figure 9The results show that the PdTe2-PdSe2 heterojunction exhibits significant saturated absorption characteristics at two wavelengths, and the normalized transmittance increases significantly with the increase of incident light intensity. However, the transmittance of pure PdTe2 and PdSe2 remains basically unchanged under the same test conditions, proving that the PdTe2-PdSe2 heterojunction has nonlinear optical response characteristics in a wider spectral range. As shown in Figure 10 The nonlinear absorption coefficient, modulation depth and saturation intensity of the heterojunction at 1100 nm are calculated by fitting to be -2.85×10 4 cm / GW, 9.03% and 3.21 GW / cm 2 , respectively. The corresponding parameters at 1550 nm are -1.29×10 5 cm / GW, 31.92% and 23.56 GW / cm 2 , respectively. Therefore, the heterojunction in the present application can be used as a saturated absorption material and applied to the field of nonlinear optics such as ultra-short pulse generation, laser protection, optical communication, precision detection, etc.

[0049] Example 2

[0050] (1) A 2-inch silicon oxide substrate with a thickness of 0.05 cm was used, and was ultrasonically cleaned in deionized water, acetone and ethanol for 20 minutes, and then dried with nitrogen.

[0051] (2) A thin film of palladium was electron beam evaporated at an evaporation rate of 1.2 Å / s for 28 minutes, with a thickness of about 2 nm.

[0052] The substrate was placed in the center of the tube furnace, and 500 mg of high-purity selenium powder was placed 4 cm upstream. After evacuating for 30 minutes under argon, the vacuum was drawn to -10 Pa, and the temperature was raised to 310°C using 250 sccm of Ar as the carrier gas. The selenium was selenized by heating for 70 minutes, and then naturally cooled to obtain a PdSe2 thin film.

[0053] (3) A 2 nm palladium thin film was evaporated again.

[0054] (4) The sample was placed in the second temperature zone of a double-temperature zone furnace, and 100 mg of high-purity tellurium powder was placed in the first temperature zone. The Ar / H2 mixed gas (500 sccm each) was purged for 3 minutes. Under atmospheric pressure, the first temperature zone was heated to 500°C and the second temperature zone was heated to 280°C using 25 sccm of Ar as the carrier gas. The tellurium was tellurized by heating for 15 minutes, and then naturally cooled to obtain a PdTe2-PdSe2 heterojunction.

[0055] Figure 11 (a) shows that a uniform and continuous wafer-level heterojunction thin film is obtained, Figure 11 (b) the Raman spectrum shows clear PdTe2 and PdSe2 characteristic peaks. As Figure 11(c) and 11(d), the open-aperture Z-scan test shows a significant saturable absorption phenomenon at 1550 nm band.

[0056] Example 3

[0057] (1) A 2-inch sapphire substrate with a thickness of 0.06 cm was used, and was ultrasonically cleaned in deionized water, acetone, and ethanol for 20 minutes, and was dried with nitrogen.

[0058] (2) A thin film of palladium was electron-beam evaporated at an evaporation rate of 1.5 Å / s and a deposition time of 25 minutes, and had a thickness of about 1 nm.

[0059] The substrate was placed in the center of the tube furnace, and 500 mg of high-purity selenium powder was placed 4 cm upstream. After evacuation for 20 minutes under argon, the vacuum was drawn to -10 Pa, and the temperature was raised to 300°C using 200 sccm of Ar as the carrier gas. Seleniumization was performed for 65 minutes, and the sample was naturally cooled to obtain a palladium diselenide thin film.

[0060] (3) A 1 nm palladium thin film was again evaporated.

[0061] (4) The sample was placed in the second temperature zone of a double-temperature-zone furnace, and 100 mg of high-purity tellurium powder was placed in the first temperature zone. The Ar / H2 mixed gas (500 sccm each) was purged for 5 minutes. Under atmospheric pressure, the first temperature zone was raised to 550°C and the second temperature zone was raised to 320°C using 30 sccm of Ar as the carrier gas. Tellurization was performed for 12 minutes, and the sample was naturally cooled to obtain a palladium ditelluride-palladium diselenide heterojunction.

[0062] Figure 12 It was shown that a palladium ditelluride-palladium diselenide heterojunction was successfully prepared, and exhibited excellent nonlinear saturable absorption performance under 1550 nm light excitation.

[0063] Comparative Example 1

[0064] The rest was the same as in Example 1, except that the order of seleniumization and tellurization was interchanged, i.e., a palladium ditelluride thin film was first grown on a sodium-calcium glass substrate with a pre-deposited palladium thin film, and the palladium ditelluride thin film was used as a substrate for growing a palladium diselenide thin film, in an attempt to prepare a vertical heterojunction. Figure 13 It can be seen from the Raman spectrum of Formula (1) that the material prepared by this method has other characteristic peaks that do not belong to palladium ditelluride or palladium diselenide, i.e., a palladium ditelluride-palladium diselenide heterojunction cannot be obtained.

[0065] Comparative Example 2

[0066] The rest was the same as in Comparative Example 1, except that the substrate used in step S1 was a sapphire substrate. The sample prepared was characterized by Raman spectroscopy, and the results are shown in Formula (2). Figure 14 It can be seen from Formula (2) that there are impurity peaks, i.e., a palladium ditelluride-palladium diselenide heterojunction also cannot be obtained.

Claims

1. A method for preparing a wafer-level PdTe2-PdSe2 vertical heterojunction thin film for a nonlinear saturable absorber, characterized in that, The method comprises the following steps: S1. A blank substrate is pretreated to remove surface impurities and contaminants; S2. A metal palladium film is deposited on the pretreated substrate obtained in step S1 by using an electron beam evaporation film plating instrument, the evaporation rate is controlled at 1.0-1.5 Å / s, the deposition time is 25-30 min, and a substrate with a metal palladium pre-deposition layer is obtained; S3. The substrate with the metal palladium pre-deposition layer obtained in step S2 is placed in the heating center region of a tube furnace, and a quartz boat containing selenium powder is placed at a distance of 2-6 cm from the upstream of the heating center; before heating and reacting, pure argon gas is introduced into the tube furnace for 10-50 min to evacuate the tube, then the vacuum pump is started to draw the system pressure to a low pressure environment of -10 Pa to -8 MPa, argon gas with a flow rate of 150-300 sccm is used as the carrier gas, the furnace temperature is raised to 260-330 ℃, and the temperature is kept for 60-80 min for the selenium reaction, and after the reaction is completed, the temperature is naturally cooled to room temperature, and a palladium diselenide film is obtained; S4. The palladium diselenide film obtained in step S3 is used as a substrate, and a metal palladium film is pre-deposited again by electron beam evaporation, and the parameters are the same as those in step S2; S5. The twice-deposited metal palladium film obtained in step S4 is placed in the second heating center of a double-temperature-zone tube furnace, and a quartz boat containing tellurium powder is placed in the first heating center of the double-temperature-zone tube furnace; before growth, the reaction chamber is cleaned with argon-hydrogen mixed gas for 1-5 min, then under atmospheric pressure, argon gas with a flow rate of 10-30 sccm is used as the carrier gas, the first temperature zone is raised to 450-650 ℃, the second temperature zone is raised to 250-450 ℃, and the temperature is kept for 8-180 min for the tellurization reaction, and after the reaction is completed, the temperature is naturally cooled to room temperature, and a wafer-level palladium ditelluride-palladium diselenide vertical heterojunction film is prepared.

2. The method of claim 1, wherein the method is characterized by: In step S1, the substrate is any one of silicon, silicon oxide, sapphire or soda lime glass.

3. The method of claim 1, wherein the method further comprises: In step S1, the substrate size is a 1-3 inch wafer, and the thickness is 0.05-1.1 centimeters.

4. The method of claim 1, wherein the method is characterized by: In step S2, the thickness of the metal palladium film is 1-10 nanometers.

5. The method for preparing wafer level PdTe2-PdSe2 vertical heterojunction thin film for nonlinear saturable absorber according to claim 1, characterized in that, In step S3, the selenium powder is high-purity selenium powder with a purity of 99.9%, and the flow rate of the pure argon gas used for evacuation is 150-500 sccm.

6. The method for preparing wafer level PdTe2-PdSe2 vertical heterojunction thin film for nonlinear saturable absorber according to claim 1, characterized in that, In step S3, the selenium reaction temperature is 300-325 ℃, and the selenium reaction time is 60-70 min.

7. The method for preparing wafer level PdTe2-PdSe2 vertical heterojunction thin film for nonlinear saturable absorber according to claim 1, characterized in that, In step S5, the tellurium powder is high-purity tellurium powder with a purity of 99.9%.

8. The method for preparing wafer level PdTe2-PdSe2 vertical heterojunction thin film for nonlinear saturable absorber according to claim 1, characterized in that, In step S5, the argon flow rate in the argon-hydrogen mixed gas is 460-520 sccm, and the hydrogen flow rate is 460-520 sccm.

9. The method for preparing wafer level PdTe2-PdSe2 vertical heterojunction thin film for nonlinear saturable absorber according to claim 1, characterized in that, In step S5, the first temperature zone heating temperature is 450-500 ℃, the second temperature zone heating temperature is 250-300 ℃, and the tellurization time is 10-20 min.

10. The wafer-level palladium ditelluride-palladium diselenide vertical heterojunction film prepared by the method of any one of claims 1-9 is used in the preparation of a nonlinear optical device.

Images