A method for preparing a tellurium single crystal thin film on a mica substrate and a tellurium single crystal thin film

Abstract

The application provides a method for preparing a tellurium single crystal thin film on a mica substrate and the tellurium single crystal thin film, and relates to the fields of low-dimensional material preparation and semiconductor technology. The method comprises the following steps: mechanically cleaving the mica substrate; performing pre-annealing treatment on the mica substrate in an ultrahigh vacuum environment to obtain an atomically flat cleavage surface; keeping the mica substrate at 135-145 DEG C, and heating a tellurium source to 300-340 DEG C, so that a tellurium molecular beam is deposited on the surface of the mica substrate to perform epitaxial growth; and performing in-situ annealing treatment on the obtained tellurium thin film in a vacuum environment after the growth is completed. The application realizes controllable preparation of a large-area and high-quality tellurium single crystal thin film on the mica substrate, the prepared tellurium single crystal thin film has a high c-axis orientation, a surface root mean square roughness is not greater than 1 nm, and a magnetoresistance value at 2K temperature is as high as 3%, and the prepared tellurium single crystal thin film is suitable for the fields of new electronic devices, sensors and topological quantum devices.

Description

Technical Field

[0001] This invention relates to the fields of low-dimensional material preparation and semiconductor technology, and in particular to a method for preparing tellurium single-crystal thin films on mica substrates and the tellurium single-crystal thin films themselves. Background Technology

[0002] Tellurium (Te), a typical narrow-bandgap p-type semiconductor, possesses a unique chain-like crystal structure and excellent physical properties, such as high carrier mobility, strong spin-orbit coupling, and potential topological states, showing application potential in nanoelectronics, optoelectronics, and spintronics. In particular, two-dimensional tellurium thin films exhibit novel physical phenomena due to quantum confinement effects, becoming a hot topic in low-dimensional materials research.

[0003] Currently, the main methods for preparing two-dimensional tellurium thin films include mechanical exfoliation, liquid phase deposition, and chemical vapor deposition (CVD). However, mechanical exfoliation is difficult to achieve large-area preparation; liquid phase deposition easily introduces impurities and defects into the film; and traditional CVD methods often fail to obtain large-area, high-quality single-crystal thin films, with grain boundaries severely affecting carrier transport performance. While molecular beam epitaxy (MBE) used in existing research can precisely control film growth at the atomic scale, the significant lattice mismatch and weak interactions between tellurium and common substrates (such as SiO2 / Si) still pose a significant challenge to directly growing high-quality, large-area, uniformly oriented tellurium single-crystal thin films on these substrates. Furthermore, the extremely narrow temperature window for large-area growth under MBE limits the controllable, large-area growth of tellurium single-crystal thin films on substrates. Achieving controllable, large-area growth of tellurium single-crystal thin films on substrates requires solving the problem of matching nucleation thermodynamics and growth kinetics at weakly interacting interfaces. Existing technologies have not yet disclosed effective and complete solutions and corresponding process parameter windows to address this technical problem. Summary of the Invention

[0004] Based on the limitations of existing technologies, this invention provides a controllable synthesis technology for preparing tellurium thin films on mica substrates by optimizing the mica substrate material. This technology provides a technical reference for achieving large-area, high-quality tellurium single-crystal thin film growth and lays the foundation for further device application development.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing tellurium single-crystal thin films on mica substrates, comprising the following steps: (1) After mechanically cleaving the mica substrate, it is placed in a molecular beam epitaxy system with a vacuum degree of less than 5×10 -7 Under Pa conditions, the mica substrate is pre-annealed to obtain an atomically flat cleavage surface; the pre-annealing temperature is 400-500℃ and the pre-annealing time is 30-90 minutes. (2) The temperature of the mica substrate is maintained at 135-145℃, and the tellurium source is heated to 300-340℃ to form a tellurium thin film on the surface of the mica substrate through a tellurium molecule beam; (3) After growth, the tellurium film is annealed in situ at 120-160℃ for 10-60 minutes.

[0006] The above preparation method obtains atomically flat cleavage surfaces by mechanically cleaving mica substrates and performing pre-annealing, eliminating the lattice mismatch limitations of traditional substrates and providing an ideal nucleation interface. Furthermore, by strictly controlling the temperature range between the substrate and the tellurium source, the migration and desorption rates of tellurium atoms at the van der Waals interface of the mica substrate are precisely matched, solving the problem of balancing nucleation thermodynamics and growth kinetics. The synergistic effect of the pre-annealing and in-situ annealing processes enables controllable epitaxial growth of large-area, high-quality tellurium single-crystal thin films on the mica surface: the pre-annealing treatment completely removes adsorbed water vapor and impurities from the mica surface, providing a clean surface for epitaxial growth; the in-situ annealing treatment improves the crystal quality of the film and releases internal stress.

[0007] In one embodiment, the mica substrate is a fluorinated phlogopite substrate with a size of 5×5 mm; the pre-annealing temperature in step (1) is 450°C and the pre-annealing time is 60 minutes.

[0008] By selecting fluorophlogopite as the specific material for the mica substrate and limiting the pre-annealing temperature and time window, stable atomic-level flatness of the substrate surface was ensured and adsorbates were effectively removed, providing clean and uniform nucleation sites for subsequent epitaxial growth and avoiding non-uniform nucleation and polycrystalline formation caused by surface contamination or excessive roughness.

[0009] In one implementation, the temperature of the mica substrate in step (2) is maintained at 140°C, which is a preferred parameter for the epitaxial growth of tellurium on the mica surface; the temperature of the tellurium source is 320°C, which can generate a stable tellurium molecular beam, ensuring the stability of the deposition process and the quality of the thin film; the vacuum degree is ≤5.0×10⁻⁶. -8 Pa.

[0010] This implementation precisely defines the synergistic parameter window of substrate temperature, tellurium source temperature, and vacuum level. Under these conditions, the surface diffusion length and nucleation density of tellurium atoms reach an optimal balance, ensuring that tellurium atoms have the most suitable adsorption energy and surface migration ability on the van der Waals surface of the mica substrate. This avoids desorption or decomposition caused by excessively high temperature, as well as disordered accumulation caused by excessively low temperature. At the same time, the ultra-high vacuum environment effectively suppresses impurity incorporation, which is a key condition for obtaining high-crystallinity single-crystal thin films.

[0011] Furthermore, as a preferred embodiment, the tellurium molecule beam is generated by a high-purity tellurium source with a purity ≥99.999%, thereby ensuring the chemical purity of the film at the source and avoiding the scattering effect of impurities on carrier transport.

[0012] In one implementation, the in-situ annealing temperature in step (3) is 140°C and the in-situ annealing time is 30 minutes.

[0013] By performing in-situ annealing at a specific temperature in a vacuum environment after growth, the rearrangement of atoms and defect repair within the film are promoted, and the interfacial stress generated by van der Waals epitaxy is effectively released, further improving the crystal integrity and surface smoothness of the film. Moreover, the annealing temperature is matched with the growth temperature, avoiding the damage to the film structure caused by thermal shock.

[0014] As one implementation method, the deposition time of the tellurium molecular bundle in step (2) is 5-60 minutes, preferably 30 minutes. By adjusting the deposition time, the thickness of the tellurium film can be controlled, and a tellurium single crystal film with moderate thickness and excellent quality can be obtained.

[0015] Secondly, this application also provides a tellurium single-crystal thin film prepared by the above method, comprising: a tellurium single-crystal layer epitaxially grown on the surface of the mica substrate.

[0016] The tellurium single crystal layer has a preferred c-axis orientation and a root mean square surface roughness ≤1 nm.

[0017] The X-ray diffraction pattern of the tellurium thin film shows only the (001) diffraction peak, and the half-width at half maximum (WHM) of the (001) diffraction peak rocking curve is no greater than 0.1°, which confirms the high c-axis orientation and single-crystal characteristics of the thin film; the low surface roughness of the thin film confirms its atomically flat surface morphology. Furthermore, the magnetoresistance of the tellurium single crystal thin film is ≥1% at 2K temperature and 9T magnetic field, with a maximum of 3%, indicating that the thin film has significant magnetoelectric transport characteristics at low temperature, which matches the excellent electrical transport performance and magnetoresistance characteristics brought about by the high-quality microstructure of the tellurium single crystal thin film. The in-plane lattice orientation of the tellurium single crystal thin film and the mica substrate exhibits sixfold symmetry. This symmetry relationship further indicates that there is a clear epitaxial growth relationship between the thin film and the substrate, and the lattice arrangement of the tellurium single crystal thin film has good matching with the mica substrate.

[0018] Beneficial effects: 1. By precisely controlling the substrate temperature (135-145℃), tellurium source temperature (300-340℃), and the synergistic effect of pre-annealing (400-500℃, 30-90 minutes) and in-situ annealing (120-160℃, 10-60 minutes), this invention achieves controllable fabrication of large-area, high-quality tellurium single-crystal thin films on mica substrates, solving the technical challenge of nucleation and high-quality single-crystal growth on mica substrates. Specifically, the pre-annealing process thoroughly removes adsorbates from the mica surface, providing a clean epitaxial growth surface; the precise control of the substrate and tellurium source temperatures, based on the lattice matching relationship and van der Waals interactions between tellurium and mica, effectively controls the nucleation thermodynamics and growth kinetics of tellurium; and the in-situ annealing process improves the crystallinity quality of the thin film and releases internal stress. The X-ray diffraction pattern of the prepared tellurium thin film showed only the (001) diffraction peak. The half-width at half maximum (WHM) of the rocking curve of the (001) diffraction peak reached 0.05°, which is far below the excellent level of 0.1°, indicating that the film has a high c-axis orientation and extremely high crystal quality. 2. The tellurium single-crystal thin film prepared by this invention has a continuous and uniform surface with a root mean square roughness of only 0.5 nm, far below 1 nm, exhibiting extremely high surface flatness. This flat surface morphology not only facilitates subsequent device fabrication but also reduces interface scattering and improves carrier transport performance. The six-fold symmetry between the thin film and the mica substrate proves that the tellurium thin film has achieved epitaxial growth on the mica substrate. The clear lattice orientation relationship between the thin film and the substrate ensures the high quality and performance stability of the thin film. 3. The tellurium single-crystal thin film prepared by this invention exhibits unique electrical transport and magnetoresistance properties. The resistance increases with decreasing temperature, displaying typical semiconductor behavior: at a low temperature of 2K, the magnetoresistance effect is very significant under a magnetic field perpendicular to the film plane, reaching as high as 3% under a 9T magnetic field, and the curve exhibits a symmetrical parabolic shape. This significant magnetoresistance effect indicates that the thin film possesses excellent electromagnetic transport properties, providing an ideal material platform for studying its fundamental physical properties and its application in novel high-performance electronic devices (such as high-sensitivity magnetic sensors and low-power transistors). Attached Figure Description

[0019] Figure 1 The X-ray diffraction pattern of the tellurium thin film in Example 1; Figure 2 The rocking curve of the Te(001) diffraction peak of the tellurium thin film in Example 1; Figure 3 The in-plane azimuth (phi) scan pattern of the tellurium thin film and mica substrate in Example 1; Figure 4 This is an atomic force microscope image of the surface morphology of the tellurium thin film in Example 1; Figure 5 The Raman spectrum of the tellurium thin film in Example 1; Figure 6 The resistance-temperature curve (2K - 300K) of the tellurium thin film in Example 1; Figure 7 The magnetoresistance curves of the tellurium thin film in Example 1 at temperatures ranging from 2K to 100K (magnetic field range -9T to 9T). Figure 8 The X-ray diffraction pattern of the tellurium thin film in Example 2; Figure 9 This is an atomic force microscope image of the surface morphology of the tellurium thin film in Example 2; Figure 10 The X-ray diffraction pattern of the tellurium thin film in Example 3; Figure 11 This is an atomic force microscope image of the surface morphology of the tellurium thin film in Example 3; Figure 12 The X-ray diffraction pattern of the mica substrate in Comparative Example 1 is shown. Figure 13 The X-ray diffraction pattern of the tellurium thin film in Comparative Example 7 is shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, all raw materials used in the following examples are commercially available. The mica substrate was fluorophlogopite, purchased from Beijing Keyi Haibo Technology Co., Ltd., with a size of 5×5 mm. The tellurium source was high-purity tellurium particles, with a purity ≥99.999%, purchased from Aladdin Reagent Company. Molecular beam epitaxy (MBE) was performed using the MBE-Komponenten-GmbH system (Germany). X-ray diffraction was performed using a Rigaku SmartLab11 X-ray diffractometer (Japan), with a CuKa radiation source and a wavelength of 1.5406 Å. Raman spectroscopy was performed using a Horiba LabRAM HR Evolution Raman spectrometer, with an excitation wavelength of 532 nm. Atomic force microscopy was performed using a Cypher ES microscope from Oxford Instruments, in tapping mode. Electrical transport and magnetoresistance properties were measured using a QuantumDesign PPMS integrated property measurement system.

[0022] Example 1 This embodiment provides a method for preparing tellurium single-crystal thin films on mica substrates, the specific steps of which are as follows: Step 1: Substrate preparation. Take a 5×5 mm fluorophlogopite substrate and mechanically cleave it in air to obtain a fresh, smooth surface.

[0023] Step 2: Sample Loading and Pre-annealing. The cleaved mica substrate is quickly loaded into the vacuum chamber of the molecular beam epitaxy (MBE) system. The chamber vacuum is then evacuated to 5.0 × 10⁻⁶. -8 Pa. The substrate temperature was raised to 450°C and held for 60 minutes to thoroughly remove adsorbed moisture and impurities from the surface.

[0024] Step 3: Epitaxial Growth. Reduce the substrate temperature to 140°C. Turn on the high-purity tellurium source (99.999% purity) source furnace and stabilize the tellurium source temperature at 320°C to generate a stable tellurium molecular beam. Deposit and grow under these conditions for 60 minutes.

[0025] Step 4: In-situ annealing. After growth, the tellurium source is turned off, and the sample is annealed at 140°C for 30 minutes in a vacuum environment to improve the crystallinity of the film and release internal stress.

[0026] The prepared thin film samples were subjected to relevant characterization tests, specifically: X-ray diffraction test: such as Figure 1 As shown, a sharp Te(001) diffraction peak appears near 2θ, which is about 25°, with no other impurity peaks, confirming that the film is a highly c-axis oriented single crystal. Figure 2 The figure shows the rocking curve of the Te(001) diffraction peak. Its full width at half maximum (FWHM) is 0.05°, which is much lower than 0.1°, indicating that the film has extremely high crystallinity. Figure 3 The in-plane azimuth (phi) scans of tellurium thin film and mica show that the Te (110) diffraction peak of tellurium thin film and the Mica (022) diffraction peak of mica both exhibit six periodic main peaks, and the peak positions correspond to each other, proving that there is a sixfold symmetry between the thin film and mica, and epitaxial growth is achieved.

[0027] Atomic force microscopy test: such as Figure 4 As shown, tellurium single crystal thin films are grown continuously and uniformly over a large area on a 5×5 mm mica substrate, exhibiting a large number of strip and sheet-like grain morphologies at the microscopic level, and the measured RMS roughness is only 0.5 nm, indicating extremely high surface smoothness of the thin film.

[0028] Raman spectroscopy test: such as Figure 5 As shown, at 92.9 cm -1 120.9 cm -1 and 138.6 cm -1 The presence of characteristic peaks of the trigonal Te crystal system confirms the tellurium crystal structure of the thin film.

[0029] Electrical transport testing: Resistance-temperature profiles were measured using a four-probe method on a comprehensive property measurement system, with temperature settings ranging from 2K to 300K. For example... Figure 6 As shown, the material resistance increases as the temperature decreases, exhibiting typical semiconductor behavior.

[0030] Magnetoresistive testing: Tested under a magnetic field perpendicular to the thin film plane, with a temperature setting of 2K to 100K and a magnetic field range of -9T to 9T. For example... Figure 7 As shown, the magnetoresistance effect is very significant at a low temperature of 2K, and the magnetoresistance value is as high as 3% under a magnetic field of 9T. Moreover, the curve is a symmetrical parabola, indicating that the thin film has excellent electromagnetic transport properties.

[0031] This embodiment achieves this by precisely controlling the substrate temperature (140℃), tellurium source temperature (320℃), pre-annealing process (450℃ / 60 minutes), in-situ annealing process (140℃ / 30 minutes), and ultra-high vacuum level (5.0×10⁻⁶). -8 The synergistic effect of Pa enables the controllable preparation of large-area, high-quality single-crystal tellurium thin films on mica substrates, solving the technical problem of obtaining large-area, high-quality single-crystal tellurium thin films on mica substrates in the prior art, and achieving excellent comprehensive performance with a surface roughness of 0.5 nm and a magnetoresistance value of 3% at 2K temperature.

[0032] Example 2 The difference between this embodiment and Embodiment 1 is that the deposition time of the tellurium molecular beam in step 3 is shortened to 30 minutes, while the remaining steps are the same as in Embodiment 1.

[0033] The characterization results are as follows: X-ray diffraction test: such as Figure 8 As shown, a sharp Te(001) diffraction peak appears near 2θ, approximately 25°, with no other impurity peaks, confirming that the material obtained under these conditions is a tellurium single-crystal thin film. Meanwhile, as... Figure 9 As shown, tellurium single crystal thin films are grown continuously and uniformly over a large area on a 5×5 mm mica substrate, exhibiting a large number of strip-shaped and sheet-shaped grain morphologies at the microscopic level. Compared with Example 1, as the deposition time is shortened, the thickness of the tellurium single crystal thin film formed on the mica substrate in Example 2 may decrease and become uneven, with some areas of the film having obvious protrusions.

[0034] This embodiment verifies that tellurium single-crystal thin films can also be prepared with a deposition time of 30 minutes, proving that the method has good adaptability to deposition time.

[0035] Example 3 The difference between this embodiment and Embodiment 1 is that the deposition time of the tellurium molecular beam in step 3 is further shortened to 5 minutes, while the remaining steps are the same as in Embodiment 1.

[0036] The characterization results are as follows: X-ray diffraction test: such as Figure 10 As shown, a sharp Te(001) diffraction peak appears near 2θ, which is about 25°, with no other impurity peaks, confirming that the material obtained under this condition is a tellurium single crystal thin film. Figure 11 As can be seen, tellurium single-crystal thin films grow continuously and uniformly over a large area on mica substrates, exhibiting a large number of strip-shaped and plate-shaped grain morphologies at the microscopic level.

[0037] This embodiment verifies that by further shortening the deposition time to the limit of 5 minutes, tellurium single-crystal thin films can still be prepared, and the film thickness may be even thinner, further demonstrating that the method is adaptable to a deposition time range of 5 to 60 minutes.

[0038] Comparative Example 1 The difference between this comparative example and Example 2 is that the substrate temperature is raised to 150°C in step 3, while the remaining steps are the same as in Example 2.

[0039] The characterization results are as follows: X-ray diffraction test: such as Figure 12 As shown, only the Mica (003) to Mica (008) diffraction peaks of the mica substrate appear, and no characteristic peaks of tellurium appear, indicating that there is no tellurium single crystal film deposition on the mica surface.

[0040] The comparison between Example 2 and Comparative Example 1 shows that when the substrate temperature rises to 150°C, effective deposition of tellurium on the mica surface cannot be achieved. This indicates that substrate temperature is a key parameter for achieving epitaxial growth of tellurium on the mica surface, and excessively high temperatures will lead to fabrication failure.

[0041] Comparative Example 2 The difference between this comparative example and Example 2 is that the substrate temperature is reduced to 130°C in step 3, while the remaining steps are the same as in Example 2.

[0042] The characterization results are as follows: X-ray diffraction test: A sharp Te(001) diffraction peak appeared near 2θ, which was about 25°. There were no other impurity peaks, confirming that the material obtained under this condition was a tellurium single crystal thin film.

[0043] However, AFM testing revealed that the prepared tellurium single crystal thin film was discontinuous on a 5×5 mm mica substrate, failing to achieve continuous and uniform growth. This may be due to the reduced temperature limiting the nucleation and growth of tellurium molecular beams on the substrate.

[0044] Comparative Example 3 The difference between this comparative example and Example 2 is that in step 1, the mica substrate is replaced with a strontium titanate single crystal substrate (SrTiO3), and the surface is ultrasonically cleaned three times with deionized water, alcohol, and formaldehyde, respectively. The remaining steps are the same as in Example 2.

[0045] The characterization results are as follows: X-ray diffraction test: Only diffraction peaks of the strontium titanate substrate were observed, and no characteristic peaks of tellurium were observed, indicating that no tellurium single crystal thin film was deposited on the surface of the strontium titanate substrate.

[0046] As can be seen from the comparison between Example 2 and Comparative Example 3, it is impossible to achieve the deposition of tellurium single crystal thin film after replacing the mica substrate with a strontium titanate substrate. This is because the mica substrate is able to achieve the epitaxial growth of tellurium single crystal thin film due to its atomically flat surface, easy cleavage to obtain a fresh surface, and van der Waals surface properties. This shows that the choice of substrate material is the key to film formation.

[0047] Comparative Example 4 The difference between this comparative example and Example 2 is that the tellurium source temperature is reduced to 200°C in step 3, while the remaining steps are the same as in Example 2.

[0048] The characterization results are as follows: X-ray diffraction test: Only the Mica (003) to Mica (008) diffraction peaks of the mica substrate were observed, and no characteristic peaks of tellurium were observed, indicating that no tellurium single crystal thin film was deposited on the mica surface.

[0049] The comparison between Example 2 and Comparative Example 4 shows that when the tellurium source temperature drops to 200°C, a stable tellurium molecular beam cannot be generated, resulting in the inability to deposit tellurium on the mica surface. This indicates that the tellurium source temperature is a key parameter for generating a stable tellurium molecular beam, and too low a temperature will result in the inability to deposit.

[0050] Comparative Example 5 The difference between this comparative example and Example 2 is that the tellurium source temperature is raised to 400°C in step 3, while the remaining steps are the same as in Example 2.

[0051] The characterization results are as follows: X-ray diffraction test: Only the Mica (003) to Mica (008) diffraction peaks of the mica substrate were observed, and no characteristic peaks of tellurium were observed, indicating that no tellurium single crystal thin film was deposited on the mica surface.

[0052] The comparison between Example 2 and Comparative Example 5 shows that when the tellurium source temperature rises to 400℃, tellurium cannot be deposited on the mica surface, indicating that there is an upper limit to the tellurium source temperature. Excessive temperature will also prevent deposition, verifying that 320℃ is the optimal parameter.

[0053] Comparative Example 6 The difference between this comparative example and Example 2 is that in step 2, the chamber vacuum is evacuated to 5.0 × 10⁻⁶. -6 Pa, the remaining steps are the same as in Example 2.

[0054] The characterization results are as follows: X-ray diffraction test: Only the Mica (003) to Mica (008) diffraction peaks of the mica substrate were observed, and no characteristic peaks of tellurium were observed, indicating that no tellurium single crystal thin film was deposited on the mica surface.

[0055] A comparison between Example 2 and Comparative Example 6 shows that when the chamber vacuum level drops to 5.0 × 10⁻⁶, -6 At a vacuum level of Pa, tellurium cannot be deposited on the surface of mica, indicating that ultra-high vacuum is a necessary condition for avoiding impurity contamination and achieving the preparation of pure single-crystal thin films.

[0056] Comparative Example 7 The difference between this comparative example and Example 2 is that in step 2, the chamber vacuum is evacuated to 5.0 × 10⁻⁶. -7 Pa, the remaining steps are the same as in Example 2.

[0057] The characterization results are as follows: X-ray diffraction test: such as Figure 13 As shown, a sharp Te(001) diffraction peak appears near 2θ, which is about 25°, but at the same time, a Te(101) thin film peak also appears near 2θ, which is about 40°. This indicates that the prepared tellurium thin film is not unidirectional and is in an intermediate state of "can form a film but the quality is deteriorated".

[0058] This may be because, under this vacuum condition, the residual gas molecules in the chamber form randomly distributed local adsorption islands on the mica surface. These adsorption sites locally shield the lattice symmetry potential field of the mica, thereby changing the adsorption orientation of Te atoms in this region, resulting in inconsistent Te nucleus orientations in different regions.

[0059] Furthermore, those skilled in the art will understand that the mica substrate is not limited to fluorophlogopite, but may also be other mica materials with layered structures and van der Waals surface properties, such as muscovite and biotite.

[0060] Obviously, the substrate temperature is not limited to 140°C, but can be adjusted within the range of 135-145°C to meet different growth requirements.

[0061] It is understood that the tellurium source temperature is not limited to 320℃, but can be adjusted within the range of 300-340℃ to control the intensity and stability of the tellurium molecular beam.

[0062] Obviously, the pre-annealing temperature is not limited to 450℃, but can be adjusted in the range of 400-500℃, and the pre-annealing time is not limited to 60 minutes, but can be adjusted in the range of 30-90 minutes.

[0063] It is understood that the in-situ annealing temperature is not limited to 140℃, but can be adjusted within the range of 120-160℃, and the in-situ annealing time is not limited to 30 minutes, but can be adjusted within the range of 10-60 minutes.

[0064] Obviously, the vacuum degree is not limited to 5.0 × 10⁻⁶. -8 Pa, can also be less than 5 × 10 -7 Adjustable within the Pa range to provide a clean growth environment.

[0065] It is understood that the deposition time is not limited to 5 minutes, 30 minutes or 60 minutes, and can be flexibly adjusted within the range of 5-60 minutes according to the required film thickness.

[0066] The embodiments disclosed in this invention are preferred embodiments, but are not limited thereto. Those skilled in the art can easily understand the spirit of this invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of this invention, they are all within the protection scope of this invention.

Claims

1. A method for preparing tellurium single-crystal thin films on mica substrates, characterized in that, Includes the following steps: (1) After mechanically cleaving the mica substrate, it is placed in a molecular beam epitaxy system with a vacuum degree of less than 5×10 -7 Under Pa conditions, the mica substrate is pre-annealed to obtain an atomically flat cleavage surface; the pre-annealing temperature is 400-500℃ and the pre-annealing time is 30-90 minutes. (2) The temperature of the mica substrate is maintained at 135-145℃, and the tellurium source is heated to 300-340℃. Tellurium thin film is formed on the surface of the mica substrate by tellurium molecular beam deposition. (3) After growth, the tellurium film is annealed in situ at 120-160℃ for 10-60 minutes.

2. The method according to claim 1, characterized in that, The mica substrate is a fluorinated phlogopite substrate, and the dimensions of the mica substrate are 5×5 mm.

3. The method according to claim 1, characterized in that, In step (1), the pre-annealing temperature is 450°C and the pre-annealing time is 60 minutes.

4. The method according to claim 3, characterized in that, The vacuum degree is ≤5.0×10 -8 Pa.

5. The method according to claim 1, characterized in that, In step (2), the temperature of the mica substrate is maintained at 140°C, and the temperature of the tellurium source is 320°C.

6. The method according to claim 1, characterized in that, In step (3), the in-situ annealing temperature is 140℃ and the in-situ annealing time is 30 minutes.

7. The method according to claim 1, characterized in that, The tellurium molecular beam is generated by a high-purity tellurium source with a purity ≥ 99.999%.

8. The method according to claim 7, characterized in that, The deposition time of the tellurium molecular beam in step (2) is 5-60 minutes.

9. A tellurium single-crystal thin film prepared by the method according to any one of claims 1-8, characterized in that, include: A tellurium single crystal layer is epitaxially grown on the surface of the mica substrate; the tellurium single crystal layer has a c-axis preferred orientation and a root mean square surface roughness ≤1nm.

10. The tellurium single-crystal thin film according to claim 9, characterized in that, The tellurium single crystal thin film has a magnetoresistance value of ≥1% at 2K temperature and 9T magnetic field, and the in-plane lattice orientation of the tellurium single crystal thin film and the mica substrate exhibits sixfold symmetry.

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