A method for preparing SiBc8 quantum dot film

Abstract

The application relates to a preparation method of a SiBc8 quantum dot film. An amorphous silicon film is deposited on a substrate through an electron beam evaporation coating method. The surface of the amorphous silicon has crystal facets. In order to obtain a quantum dot film containing a SiBc8 phase, a tantalum oxide film is deposited on the amorphous silicon film through a magnetron sputtering method. The tantalum oxide and the amorphous silicon are in mutual contact, can induce the amorphous silicon film to grow along a (111) crystal face to be a nanocrystalline silicon film, and then a metal tantalum film is deposited on the surface of the tantalum oxide film through the electron beam evaporation coating method. The metal tantalum can exert residual stress on the surface of the nanocrystalline silicon film, so that the Si-Si bond angle in the nanocrystalline silicon film is increased, the Si-I phase is changed into the SiBc8 phase, and after the nanocrystalline silicon / tantalum oxide / metal tantalum laminated film is annealed and pickled, the silicon quantum dot film containing the SiBc8 phase is obtained. Compared with the silicon quantum dot of the Si-I phase, the photoelectric conversion efficiency of the SiBc8 quantum dot film is higher.

Description

Technical Field

[0001] The present application relates to the field of optoelectronic materials, and in particular to a method for preparing a SiBc8 quantum dot film. Background Art

[0002] Silicon quantum dots can make full use of high-energy photons due to the quantum confinement effect, reduce energy loss and improve luminous efficiency. Therefore, they have high application prospects in single-electron transistors, optoelectronic integration and bioimaging. The excellent properties of silicon quantum dots, such as abundant raw materials, non-toxicity, adjustable emission wavelength and good biocompatibility, have also made them a research hotspot that has attracted much attention in silicon nanocrystals.

[0003] The preparation methods of silicon quantum dots can be divided into two categories. One is to directly prepare silicon nanocrystals using advanced but expensive nano-processing technologies such as electron beam exposure and reactive ion etching; the other is to use self-assembly growth technology to form large-area silicon nanocrystal films through growth mechanisms such as nucleation, aggregation, growth, and phase change of atoms, molecules or corresponding precursors.

[0004] Most of the silicon quantum dots prepared by these two methods are diamond structure (Si-I) phases that are stable at room temperature and pressure. They have indirect band gap characteristics with a band gap width of 1.12eV; however, the allotrope SiBc8 phase of the Si-I phase is a direct band gap with a band gap width of 0.03eV. The overlapping area between the light absorption spectrum and the solar energy spectrum is larger than that of the Si-I phase, but the luminescence threshold energy is much lower than that of the Si-I phase. Under the same light conditions, the SiBc8 phase produces more multi-excitons. The existence of the multi-exciton effect enables short-wavelength photons to generate multiple electron-hole pairs, which can effectively improve the conversion efficiency of solar cells. Compared with the Si-I phase, the SiBc8 phase is a better material for achieving enhanced multi-exciton effects in solar cells and laser detection, but there is currently no relevant method for directly preparing SiBc8 quantum dot films. Summary of the Invention

[0005] In view of the above problems, the core of this application is to provide a method for preparing SiBc8 quantum dot thin film, which can fill the technical gap in the preparation method of SiBc8 quantum dot thin film, improve the performance of quantum dot thin film, thereby improving the photoelectric conversion rate of solar cells, and better apply it to the field of laser detection.

[0006] To solve the above technical problems, the application provides a preparation method of a SiBc8 quantum dot film, which comprises the following steps: selecting a silicon wafer or glass as a substrate and pretreating the substrate; depositing an amorphous silicon film on the substrate by an electron beam evaporation coating method; depositing a tantalum oxide film on the amorphous silicon film by a magnetron sputtering method, so that the amorphous silicon film grows along a (111) crystal plane to form a nanocrystalline silicon film; depositing a metal tantalum film on the surface of the tantalum oxide film by the electron beam evaporation coating method, to obtain a nanocrystalline silicon / tantalum oxide / metal tantalum laminated film; performing annealing treatment on the nanocrystalline silicon / tantalum oxide / metal tantalum laminated film; and pickling the nanocrystalline silicon / tantalum oxide / metal tantalum laminated film to remove the tantalum oxide film and the metal tantalum film, so as to obtain a silicon quantum dot film containing a SiBc8 phase.

[0007] In a feasible implementation manner, the glass is quartz glass or ITO glass, and the pretreatment adopts an RCA process.

[0008] In a feasible implementation manner, the step of depositing an amorphous silicon film on the substrate by the electron beam evaporation coating method comprises the following steps: adding silicon particles with a purity greater than 99.9999% into a crucible and adjusting the crucible to a coating position; under a vacuum condition, controlling the substrate temperature of the substrate to be 150-350 ℃, rotating the substrate, adjusting the electron gun beam current to be 118-132 mA, starting to evaporate the silicon particles to deposit the amorphous silicon film on the lower surface of the substrate after the electron gun is pre-evaporated to a predetermined time, and coating for 30 s-5 min; after coating, the amorphous silicon film is continuously heated to a set time, and then naturally cooled.

[0009] In a feasible implementation manner, the step of depositing a tantalum oxide film on the amorphous silicon film by the magnetron sputtering method comprises the following steps: taking a metal tantalum target with a purity greater than 99.95% as a sputtering target material, under a vacuum condition, introducing a sputtering gas Ar and a reaction gas O2, setting the deposition temperature to be 200 ℃-380 ℃, setting the sputtering power to be 80 W-90 W, starting to sputter to deposit the tantalum oxide film on the surface of the amorphous silicon film, and after coating is completed, continuously keeping warm to a set time, and then cooling to 80 ℃, to obtain a nanocrystalline silicon / tantalum oxide laminated film.

[0010] In a feasible implementation, the use of electron beam evaporation coating method to deposit a metal tantalum film on the surface of the tantalum oxide film includes: adding metal tantalum with a purity greater than 99.9999% into a crucible and adjusting the crucible to a coating position, controlling the substrate temperature of the nanocrystalline silicon / tantalum oxide stacked film to 200°C-320°C under vacuum conditions, rotating the nanocrystalline silicon / tantalum oxide stacked film, adjusting the electron gun beam current to 133-158mA, and starting to evaporate the metal tantalum after the electron gun pre-evaporates for a predetermined time to deposit the metal tantalum film on the lower surface of the nanocrystalline silicon / tantalum oxide stacked film. After coating for 3-5 minutes, a nanocrystalline silicon / tantalum oxide / metal tantalum stacked film is obtained, and then the nanocrystalline silicon / tantalum oxide / metal tantalum stacked film is continuously heated for a set time and then naturally cooled.

[0011] In a feasible implementation, the annealing treatment of the nanocrystalline silicon / tantalum oxide / metal tantalum stacked film is as follows: passing a nitrogen-hydrogen mixture at 400°C-670°C, annealing the nanocrystalline silicon / tantalum oxide / metal tantalum stacked film for 1-20 minutes at a pressure greater than the standard atmospheric pressure of 1.2 Pa, and then naturally cooling to 80°C.

[0012] In a feasible implementation, the acid used for pickling is a mixture of deionized water, hydrofluoric acid and hot concentrated sulfuric acid.

[0013] Preferably, the volume ratio of the deionized water, hydrofluoric acid and hot concentrated sulfuric acid mixture is 100:20:30.

[0014] In a feasible implementation, the proportion of hydrogen in the nitrogen-hydrogen mixed gas is 2%.

[0015] In a feasible implementation, the argon-oxygen ratio of the sputtering gas Ar and the reaction gas O2 is 4:1, the fixed oxygen flow rate is 6 sccm, and the gas pressure is 1.6 Pa.

[0016] The present application provides a method for preparing a SiBc8 quantum dot film, which comprises selecting a silicon wafer or glass as a substrate and pre-treating the substrate; depositing an amorphous silicon film on the substrate by electron beam evaporation coating method, wherein the surface of the amorphous silicon has various crystal facets, and different crystal faces have different effects on the film structure; in order to obtain a quantum dot film containing SiBc8 phase, a tantalum oxide film is deposited on the amorphous silicon film by magnetron sputtering method; when the metal target material collides with the amorphous silicon film, tantalum oxide is generated due to energy conversion and reaction gas combination; the tantalum oxide and the amorphous silicon contact each other, which can induce the amorphous silicon film to preferentially grow into a nanocrystalline silicon film along the (111) crystal plane; and then depositing a metal tantalum film on the surface of the tantalum oxide film by electron beam evaporation coating method, thereby obtaining a nanocrystalline silicon film. The silicon / tantalum oxide / metal tantalum stacked film, the metal tantalum film can exert residual stress on the surface of the nanocrystalline silicon film, so that the Si-Si bond angle in the crystalline silicon lattice of the nanocrystalline silicon film increases, and the Si-I phase is transformed into the SiBc8 phase; the nanocrystalline silicon / tantalum oxide / metal tantalum stacked film is annealed to form silicon quantum dots; the nanocrystalline silicon / tantalum oxide / metal tantalum stacked film is pickled to remove the tantalum oxide film and the metal tantalum film to obtain a silicon quantum dot film containing the SiBc8 phase. Compared with the silicon quantum dots prepared in the prior art with a diamond structure (Si-I) phase, the silicon quantum dot film containing the SiBc8 phase has a higher efficiency in converting light energy into electrical energy, can improve the photoelectric conversion rate of solar cells, and can be better applied in the field of laser detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. Throughout the accompanying drawings, the same reference numerals are used to denote the same components.

[0018] Figure 1 A flow chart of a method for preparing a SiBc8 quantum dot film provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will describe in detail the embodiments of the technical solution of the present application in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and cannot be used to limit the scope of protection of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" in the specification and claims of the present application and the above-mentioned description of the drawings and any variations thereof are intended to cover non-exclusive inclusions.

[0020] The core of this application is to provide a method for preparing SiBc8 quantum dot film, which can fill the technical gap in the preparation method of SiBc8 quantum dot film, improve the performance of quantum dot film, thereby improving the photoelectric conversion rate of solar cells, and better apply it to the field of laser detection.

[0021] Figure 1 A flow chart of a method for preparing a SiBc8 quantum dot film provided in an embodiment of the present invention is shown in FIG. Figure 1 shown.

[0022] S01: Select silicon wafer or glass as the substrate and pre-treat the substrate.

[0023] The glass can be quartz glass or ITO glass. The purpose of pretreatment is to clean and remove chemical pollutants and particulate impurities on the surface of the substrate. The RCA cleaning process can be adopted, and the existing RCA cleaning equipment can be used to remove organic contamination on the surface of the substrate, dissolve the oxide film on the surface of the substrate, and remove impurities such as particles and metals to passivate the surface of the substrate. The cleanliness of the substrate surface will directly affect the adhesion between the subsequent thin film and the substrate.

[0024] S02: depositing an amorphous silicon thin film on the substrate by electron beam evaporation coating method.

[0025] Silicon particles are evaporated by electron beam heating, causing a large number of silicon atoms and molecules to vaporize, migrate upward and deposit on the lower surface of the substrate to form an amorphous silicon film. The surface of the amorphous silicon has various crystal facets, and different crystal faces have different effects on the film structure. In order to obtain a quantum dot film containing SiBc8 phase, it is necessary to induce the growth of the (111) crystal face of the amorphous silicon film.

[0026] S03: depositing a tantalum oxide film on the amorphous silicon film by magnetron sputtering to achieve preferential growth of the amorphous silicon film into a nanocrystalline silicon film along the (111) crystal plane.

[0027] Since tantalum has a high melting point and is a refractory metal, a tantalum oxide film is deposited on an amorphous silicon film using magnetron sputtering. When metallic tantalum collides with the amorphous silicon film, energy conversion and reaction gas combination generate tantalum oxide. Under the action of an electric field, tantalum oxide is deposited on the amorphous silicon film to form a tantalum oxide film. After tantalum oxide contacts amorphous silicon, it can induce the amorphous silicon film to preferentially grow into a nanocrystalline silicon film along the (111) crystal plane, thereby obtaining a nanocrystalline silicon / tantalum oxide stacked film.

[0028] S04: Depositing a metal tantalum film on the surface of the tantalum oxide film using an electron beam evaporation coating method to obtain a nanocrystalline silicon / tantalum oxide / metal tantalum stacked film.

[0029] A metal tantalum film is then evaporated and deposited on the tantalum oxide film to obtain a three-layer structure of nanocrystalline silicon / tantalum oxide / metal tantalum stacked film. The metal tantalum film can exert residual stress on the surface of the nanocrystalline silicon film through the tantalum oxide film as a transition layer, thereby increasing the Si-Si bond angle in the silicon lattice of the nanocrystalline silicon film and starting to transform from the Si-I phase to the SiBc8 phase.

[0030] S05: Annealing the nanocrystalline silicon / tantalum oxide / metal tantalum stacked film to form silicon quantum dots.

[0031] S06: Acid-washing the nanocrystalline silicon / tantalum oxide / metal tantalum laminate film to remove the tantalum oxide film and the metal tantalum film to obtain a silicon quantum dot film containing a SiBc8 phase. S01, S02, S03, S04, S05, and S06 are not intended to limit the order of the method steps.

[0032] Example 1

[0033] The quartz glass cleaned by the RCA process is fixed on the substrate holder, and silicon particles with a purity of 99.9999% are added to the crucible. Preferably, the silicon particles are intrinsic zone melting silicon particles. The crucible is adjusted to the coating position. Under the vacuum condition of 4×10-4Pa, the substrate temperature of the substrate is controlled to 200°C and the rotation rate of the substrate is 20 rpm. The electron gun power is turned on and the electron gun beam current is adjusted to 130mA. After the electron gun pre-evaporates for 2 minutes, it is aimed at the silicon particles in the crucible and the amorphous silicon film is started to be evaporated. The coating time is 5 minutes. After the coating is completed, the electron gun beam current is turned off. The amorphous silicon film is continuously heated for 3 minutes and then cooled naturally.

[0034] A tantalum target with a purity of 99.95% was used as the sputtering target, and the target-substrate distance was controlled to be 6 cm. The amorphous silicon film obtained in the above steps was placed on the coating rack, the magnetron sputtering chamber door was closed, and the mechanical pump and molecular pump switch buttons were turned on in sequence to start extracting the vacuum in the chamber. When the instrument showed that the pressure in the chamber dropped to 2×10-4Pa, sputtering gas Ar and reaction gas O2 were introduced, with a fixed oxygen flow rate of 6sccm, an argon-oxygen ratio of 4:1, and a gas pressure of 1.6Pa. Then the deposition temperature was set to 200℃, and the sputtering was continued. The sputtering power is 80W. After pre-sputtering for 3 minutes to effectively remove the residual impurities on the surface of the metal tantalum target, sputtering is started to deposit a tantalum oxide film on the surface of the amorphous silicon film. Then the reaction power is set to 0W and deposition is carried out for 5 minutes. Then, the temperature is kept at 5 minutes to ensure that the tantalum oxide film can grow fully. Then, while keeping the original sputtering atmosphere and working pressure unchanged, the temperature is lowered to 80°C. The tantalum oxide film induces the amorphous silicon film to preferentially grow into a nanocrystalline silicon film along the (111) crystal plane to obtain a nanocrystalline silicon / tantalum oxide stacked film.

[0035] The nanocrystalline silicon / tantalum oxide / metallic tantalum stacked film is placed into a vacuum annealing furnace, 450℃ nitrogen-hydrogen mixed gas is introduced, the hydrogen content in the nitrogen-hydrogen mixed gas is 2%, the nanocrystalline silicon / tantalum oxide / metallic tantalum stacked film is annealed for 20min under a pressure of 1.2Pa greater than the standard atmospheric pressure, after the annealing, the original gas atmosphere and working pressure are kept unchanged, and the temperature is naturally reduced to 80℃.

[0036] The nanocrystalline silicon / tantalum oxide / metallic tantalum stacked film is placed into a vacuum annealing furnace, 450℃ nitrogen-hydrogen mixed gas is introduced, the hydrogen content in the nitrogen-hydrogen mixed gas is 2%, the nanocrystalline silicon / tantalum oxide / metallic tantalum stacked film is annealed for 20min under a pressure of 1.2Pa greater than the standard atmospheric pressure, after the annealing, the original gas atmosphere and working pressure are kept unchanged, and the temperature is naturally reduced to 80℃.

[0037] The nanocrystalline silicon / tantalum oxide / metallic tantalum stacked film is placed into a vacuum annealing furnace, 450℃ nitrogen-hydrogen mixed gas is introduced, the hydrogen content in the nitrogen-hydrogen mixed gas is 2%, the nanocrystalline silicon / tantalum oxide / metallic tantalum stacked film is annealed for 20min under a pressure of 1.2Pa greater than the standard atmospheric pressure, after the annealing, the original gas atmosphere and working pressure are kept unchanged, and the temperature is naturally reduced to 80℃.

[0038] Example 2

[0039] The RCA process cleaned quartz glass is fixed on the substrate holder, silicon particles with a purity of 99.9999% are added into the crucible, preferably, intrinsic zone melting silicon particles, the crucible is adjusted to the film deposition position, under the condition of vacuum 4*10-4Pa, the substrate temperature of the base body is controlled to be 150℃, the rotation rate of the base body is 20r / min, the electron gun power supply is turned on, the electron gun beam current is adjusted to 118mA, after the electron gun is pre-evaporated for 2min, the silicon particles in the crucible are aligned, the amorphous silicon film is started to be deposited, the film deposition time is 30s, after the film deposition is completed, the electron gun beam current is turned off, the amorphous silicon film is continuously heated for 3min, and then the temperature is naturally reduced.

[0040] A tantalum target with a purity of 99.95% was used as the sputtering target, and the target-substrate distance was controlled to be 6 cm. The amorphous silicon film obtained in the above steps was placed on the coating rack, the magnetron sputtering chamber door was closed, and the mechanical pump and molecular pump switch buttons were turned on in sequence to start extracting the vacuum in the chamber. When the instrument showed that the pressure in the chamber dropped to 2×10-4Pa, sputtering gas Ar and reaction gas O2 were introduced, with a fixed oxygen flow rate of 6sccm, an argon-oxygen ratio of 4:1, and a gas pressure of 1.6Pa. Then the deposition temperature was set to 200℃, and the sputtering was continued. The sputtering power is 80W. After pre-sputtering for 3 minutes to effectively remove the residual impurities on the surface of the metal tantalum target, sputtering is started to deposit a tantalum oxide film on the surface of the amorphous silicon film. Then the reaction power is set to 0W and deposition is carried out for 5 minutes. Then, the temperature is kept at 5 minutes to ensure that the tantalum oxide film can grow fully. Then, while keeping the original sputtering atmosphere and working pressure unchanged, the temperature is lowered to 80°C. The tantalum oxide film induces the amorphous silicon film to preferentially grow into a nanocrystalline silicon film along the (111) crystal plane to obtain a nanocrystalline silicon / tantalum oxide stacked film.

[0041] The nanocrystalline silicon / tantalum oxide laminated film was fixed on the substrate holder, and metallic tantalum with a purity of 99.9999% was added into the crucible. The crucible was adjusted to the coating position. Under the vacuum condition of 4×10-4Pa, the substrate temperature of the substrate was controlled to 200°C, the rotation rate of the substrate was 15 rpm, the electron gun power was turned on, and the electron gun beam was adjusted to 133 mA. After the electron gun was pre-evaporated for 2 minutes, it was aimed at the metallic tantalum in the crucible and the metallic tantalum film was started to be evaporated. The coating time was 3 minutes. After the coating was completed, the electron gun beam was turned off, and after continuous heating for 3 minutes, the temperature was naturally lowered to obtain the nanocrystalline silicon / tantalum oxide / metallic tantalum laminated film.

[0042] The nanocrystalline silicon / tantalum oxide / metal tantalum stacked film was placed in a vacuum annealing furnace and introduced into a nitrogen-hydrogen mixture at 400°C, in which hydrogen accounted for 2%. The nanocrystalline silicon / tantalum oxide / metal tantalum stacked film was annealed for 1 minute at a pressure 1.2 Pa greater than the standard atmospheric pressure. After the annealing was completed, the temperature was naturally lowered to 80°C while maintaining the original atmosphere and working pressure unchanged.

[0043] A mixture of deionized water, hydrofluoric acid, and hot concentrated sulfuric acid in a volume ratio of 100:20:30 was prepared, and the nanocrystalline silicon / tantalum oxide / metallic tantalum laminated film was immersed in the prepared mixture to remove the tantalum oxide and metal tantalum films to obtain a silicon quantum dot film containing the SiBc8 phase with a SiBc8 phase content of 15%.

[0044] Example 3

[0045] The quartz glass cleaned by the RCA process is fixed on the substrate holder, and silicon particles with a purity of 99.9999% are added to the crucible. Preferably, the silicon particles are intrinsic zone melting silicon particles. The crucible is adjusted to the coating position. Under the condition of vacuum of 4×10-4Pa, the substrate temperature of the substrate is controlled to 350°C and the rotation rate of the substrate is 20 rpm. The electron gun power is turned on and the electron gun beam current is adjusted to 132 mA. After the electron gun pre-evaporates for 2 minutes, it is aimed at the silicon particles in the crucible and the amorphous silicon film is started to be evaporated. The coating time is 5 minutes. After the coating is completed, the electron gun beam current is turned off. The amorphous silicon film is continuously heated for 3 minutes and then cooled naturally.

[0046] A tantalum target with a purity of 99.95% was used as the sputtering target, and the target-substrate distance was controlled to be 6 cm. The amorphous silicon film obtained in the above steps was placed on the coating rack, the magnetron sputtering chamber door was closed, and the mechanical pump and molecular pump switch buttons were turned on in sequence to start extracting the vacuum in the chamber. When the instrument showed that the pressure in the chamber dropped to 2×10-4Pa, sputtering gas Ar and reaction gas O2 were introduced, with a fixed oxygen flow rate of 6sccm, an argon-oxygen ratio of 4:1, and a gas pressure of 1.6Pa. Then the deposition temperature was set to 380℃, and the sputtering was continued. The sputtering power is 90W. After pre-sputtering for 3 minutes to effectively remove the residual impurities on the surface of the metal tantalum target, sputtering is started to deposit a tantalum oxide film on the surface of the amorphous silicon film. Then the reaction power is set to 0W and deposition is carried out for 5 minutes. Then, the temperature is kept at 5 minutes to ensure that the tantalum oxide film can grow fully. Then, while keeping the original sputtering atmosphere and working pressure unchanged, the temperature is lowered to 80°C. The tantalum oxide film induces the amorphous silicon film to preferentially grow into a nanocrystalline silicon film along the (111) crystal plane to obtain a nanocrystalline silicon / tantalum oxide stacked film.

[0047] The nanocrystalline silicon / tantalum oxide laminated film was fixed on the substrate holder, and metallic tantalum with a purity of 99.9999% was added to the crucible. The crucible was adjusted to the coating position. Under the vacuum condition of 4×10-4Pa, the substrate temperature of the substrate was controlled to 320°C, the rotation rate of the substrate was 15 rpm, the electron gun power was turned on, and the electron gun beam was adjusted to 158 mA. After the electron gun was pre-evaporated for 2 minutes, it was aimed at the metallic tantalum in the crucible and the metallic tantalum film was started to be evaporated. The coating time was 5 minutes. After the coating was completed, the electron gun beam was turned off, and after continuous heating for 3 minutes, the temperature was naturally lowered to obtain the nanocrystalline silicon / tantalum oxide / metallic tantalum laminated film.

[0048] The nanocrystalline silicon / tantalum oxide / metal tantalum stacked film was placed in a vacuum annealing furnace and introduced into a nitrogen-hydrogen mixture at 670°C, with hydrogen accounting for 2%. The nanocrystalline silicon / tantalum oxide / metal tantalum stacked film was annealed for 20 minutes at a pressure 1.2 Pa greater than the standard atmospheric pressure. After the annealing was completed, the temperature was naturally lowered to 80°C while maintaining the original atmosphere and working pressure unchanged.

[0049] A mixture of deionized water, hydrofluoric acid, and hot concentrated sulfuric acid in a volume ratio of 100:20:30 was prepared, and the nanocrystalline silicon / tantalum oxide / metallic tantalum laminate film was immersed in the prepared mixture to remove the tantalum oxide and metal tantalum films to obtain a silicon quantum dot film containing the SiBc8 phase, with a SiBc8 phase content of 35%.

[0050] The TEMDS500 thin film preparation system can be used to implement the electron beam evaporation coating method in Examples 1 to 3. Example 1 is the best implementation method, which can produce a silicon quantum dot film with a SiBc8 phase content of 45%. Compared with the silicon quantum dots prepared in the prior art with a diamond structure (Si-I) phase, under the same lighting conditions, the silicon quantum dot film containing the SiBc8 phase produces more multi-excitons. Therefore, the SiBc8 quantum dot film is more efficient in converting light energy into electrical energy. This material can effectively improve the photoelectric conversion rate of solar cells. Compared with existing silicon quantum dot films, it can also be better used in the field of laser detection. The preparation method provided in this application is based on conventional equipment in the semiconductor industry. SiBc8 quantum dot films with a high SiBc8 phase content can be obtained by induced growth without high pressure, which is conducive to the realization of industrial mass production.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for preparing a SiBc8 quantum dot film, characterized in that: The following steps are involved: Selecting a silicon wafer or glass as a substrate and pre-treating the substrate; depositing an amorphous silicon thin film on the substrate by electron beam evaporation; Depositing a tantalum oxide film on the amorphous silicon film by magnetron sputtering to achieve preferential growth of the amorphous silicon film along the (111) crystal plane into a nanocrystalline silicon film; Depositing a metal tantalum film on the surface of the tantalum oxide film by electron beam evaporation to obtain a nanocrystalline silicon / tantalum oxide / tantalum metal stacked film; annealing the nanocrystalline silicon / tantalum oxide / metal tantalum laminate film; The nanocrystalline silicon / tantalum oxide / metal tantalum stacked film is pickled to remove the tantalum oxide film and the metal tantalum film to obtain a silicon quantum dot film containing SiBc8 phase.

2. The method for preparing a SiBc8 quantum dot thin film according to claim 1, wherein: The glass is quartz glass or ITO glass, and the pretreatment adopts RCA process.

3. The method for preparing a SiBc8 quantum dot thin film according to claim 1, characterized in that: Depositing an amorphous silicon thin film on the substrate by electron beam evaporation coating method comprises: Silicon particles with a purity greater than 99.9999% are added to a crucible and the crucible is adjusted to a coating position. Under vacuum conditions, the substrate temperature of the substrate is controlled to be 150-350°C, the substrate is rotated, and the electron gun beam current is adjusted to 118-132 mA. After the electron gun pre-evaporates for a predetermined time, evaporation is started on the silicon particles to deposit the amorphous silicon thin film on the lower surface of the substrate. The coating time is 30 seconds to 5 minutes. After coating, the amorphous silicon thin film is continuously heated for a set time and then cooled naturally.

4. The method for preparing a SiBc8 quantum dot thin film according to claim 1, wherein: The depositing of a tantalum oxide film on the amorphous silicon film by magnetron sputtering comprises: A metal tantalum target with a purity greater than 99.95% is used as a sputtering target. Under vacuum conditions, sputtering gas Ar and reaction gas O2 are introduced, the deposition temperature is set to 200℃-380℃, the sputtering power is 80W-90W, and sputtering is started to deposit the tantalum oxide film on the surface of the amorphous silicon film. After the coating is completed, the temperature is maintained for the set time, and then the temperature is lowered to 80℃ to obtain a nanocrystalline silicon / tantalum oxide laminated film.

5. The method for preparing a SiBc8 quantum dot thin film according to claim 1, characterized in that: Depositing a metal tantalum film on the surface of the tantalum oxide film by electron beam evaporation coating method comprises: Add metallic tantalum with a purity greater than 99.9999% into a crucible and adjust the crucible to a coating position. Under vacuum conditions, control the substrate temperature of the nanocrystalline silicon / tantalum oxide laminated film to 200°C-320°C, rotate the nanocrystalline silicon / tantalum oxide laminated film, adjust the electron gun beam current to 133-158 mA, and start evaporation of the metallic tantalum after the electron gun pre-evaporates for a predetermined time to deposit the metallic tantalum thin film on the lower surface of the nanocrystalline silicon / tantalum oxide laminated film. After coating for 3-5 minutes, a nanocrystalline silicon / tantalum oxide / metallic tantalum laminated film is obtained. Then, the nanocrystalline silicon / tantalum oxide / metallic tantalum laminated film is continuously heated for a set time and then cooled naturally.

6. The method for preparing a SiBc8 quantum dot thin film according to claim 1, characterized in that: The annealing treatment of the nanocrystalline silicon / tantalum oxide / metal tantalum stacked film is as follows: The nanocrystalline silicon / tantalum oxide / metallic tantalum stacked film is annealed for 1-20 minutes by passing a nitrogen-hydrogen mixture at 400° C.-670° C. at a pressure 1.2 Pa greater than the standard atmospheric pressure, and then naturally cooled to 80° C.

7. The method for preparing a SiBc8 quantum dot thin film according to claim 1, characterized in that: The acid used in the pickling is a mixed solution of deionized water, hydrofluoric acid and hot concentrated sulfuric acid.

8. The method for preparing a SiBc8 quantum dot thin film according to claim 7, characterized in that: The volume ratio of the deionized water, hydrofluoric acid and hot concentrated sulfuric acid mixture is 100:20:

30.

9. The method for preparing a SiBc8 quantum dot thin film according to claim 6, characterized in that: The hydrogen content in the nitrogen-hydrogen mixed gas is 2%.

10. The method for preparing a SiBc8 quantum dot thin film according to claim 4, characterized in that: The argon-oxygen ratio of the sputtering gas Ar to the reaction gas O2 is 4:1, the fixed oxygen flow rate is 6 sccm, and the gas pressure is 1.6 Pa.

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