Method for preparing diamond germanium vacancy color center in fixed area based on MPCVD method graphical film

Abstract

The invention discloses a method for preparing a diamond germanium vacancy color center in a patterned film fixed area based on an MPCVD method, and aims to solve the problems that only a GeV color center ensemble can be prepared and a color center area is difficult to longitudinally control in an existing CVD method. The method for preparing the diamond germanium vacancy color center comprises the following steps: 1, ultrasonically cleaning a diamond substrate; 2, spin-coating photoresist on the surface of the diamond substrate, forming a patterned mask by adopting a photoetching process, and depositing a germanium film on the patterned mask by adopting a physical vapor deposition process to obtain a diamond substrate with a patterned germanium film; and 3, increasing the air pressure and the microwave power to enable the temperature of the diamond substrate to reach 800-900 DEG C, and introducing methane to perform epitaxial growth and form a GeV color center. According to the method, the graphical Ge thin film is used as a germanium source, the Ge element is etched by hydrogen in the CVD method process, then short-time diamond growth is carried out, and vacancies are generated in the process, so that the GeV color center with excellent performance is formed.

Description

Technical Field

[0001] The present invention belongs to the fields of semiconductor material growth and quantum technology, and particularly relates to a method for epitaxial growth of diamond films and preparation of GeV color centers. Background Art

[0002] Diamond, as a new type of semiconductor material, with its excellent optical transparency, high thermal conductivity, and wide bandgap width, shows great application potential in many frontier fields such as semiconductor technology, quantum information science, and optical devices, and is known as the "ultimate semiconductor".

[0003] When impurity atoms such as nitrogen, silicon, or germanium are introduced into the diamond lattice by physical or chemical means, vacancy defects will be formed, and then luminescence centers in the crystal, namely color centers, will be generated. These color centers have the characteristics of quantum light sources and can be widely used in fields such as quantum computing, quantum communication, and quantum detection, showing broad application prospects. The formation of color centers depends on the participation of vacancies in the crystal.

[0004] Currently, common methods for preparing vacancy color centers include ion implantation and chemical vapor deposition (CVD). The ion implantation method directly dopes impurity elements into diamond by physical means. Although it can efficiently generate vacancies, particle bombardment will inevitably cause graphitization effects on the diamond surface, causing irreversible damage to the lattice structure, and this damage cannot be repaired by annealing, thus significantly affecting the luminescence performance of color centers. In addition, the doping efficiency of the ion implantation method is relatively low.

[0005] The chemical vapor deposition method is an effective method for preparing high-quality color centers and causes less damage to the diamond lattice. However, when preparing a single GeV color center (an important type of color center), the CVD method usually can only prepare a color center ensemble, that is, a structure composed of multiple GeV color centers. There will be mutual interference between the light sources in this ensemble, resulting in a decrease in luminescence efficiency, which greatly limits the further application of GeV color centers as quantum light sources in the field of quantum information physics. Therefore, achieving the directional and regional preparation of GeV color centers is crucial.

[0006] Traditional methods for preparing GeV color centers mainly include the CVD method and the ion implantation method. The CVD method can control the thickness of the epitaxial layer by controlling the growth time, thereby realizing the control of the color center distribution in the longitudinal direction. However, due to the limitations of gas phase properties, the CVD method is difficult to achieve precise control in the transverse direction, resulting in a relatively uniform distribution of color centers in the transverse direction. The ion implantation method can introduce relevant ions by precisely calibrating the target area to achieve the control of the color center distribution in the transverse direction, but it cannot achieve precise control in the longitudinal direction and can only roughly limit the longitudinal range by adjusting the energy.

[0007] At the application level, if GeV color centers are used as quantum antennas, they should be as close to the surface as possible. However, it is difficult to fabricate shallow color centers by ion implantation, which cannot meet this application requirement. In contrast, CVD method is easier to fabricate shallow color centers. However, since the germanium source is directly placed inside the cavity, it is difficult to precisely control the concentration, and the uniform distribution of gas in the cavity makes the distribution of color centers uniform in the transverse direction, making it difficult to fabricate GeV color centers with excellent luminescence performance. Summary of the Invention

[0008] The present invention provides a method for obtaining GeV color centers in a defined region on high-temperature and high-pressure diamond using a patterned germanium thin film, aiming at the problems that the existing CVD method can only fabricate GeV color center ensembles and it is difficult to longitudinally control the color center region.

[0009] The method for fabricating diamond germanium vacancy color centers in a defined region based on the MPCVD method by patterning thin films is realized according to the following steps:

[0010] I. Cleaning:

[0011] Ultrasonically clean the high-temperature and high-pressure diamond substrate to obtain the cleaned diamond substrate;

[0012] II. Preparing the surface germanium distribution pattern:

[0013] a. Spin-coat photoresist uniformly on the surface of the cleaned diamond substrate, dry and cure the photoresist, then put it into a lithography machine and perform lithography according to the germanium thin film pattern. After soaking in the developer, a patterned mask is formed;

[0014] b. Deposit a germanium thin film on the patterned mask by physical vapor deposition process. After soaking in the stripping solution and cleaning, a diamond substrate with a patterned germanium thin film is obtained. The patterned germanium thin film is in the form of a nanodot matrix;

[0015] III. Etching and growth:

[0016] c. Put the diamond substrate with the patterned germanium thin film into the CVD growth chamber, close the chamber and evacuate, then introduce hydrogen to activate the plasma, increase the gas pressure and microwave power to make the temperature of the diamond substrate with the patterned germanium thin film reach 800 - 900 °C, and introduce methane for epitaxial growth to form GeV color centers;

[0017] d. After the epitaxial growth is completed, gradually reduce the gas pressure and microwave power in the CVD growth chamber, let the gas out and take out the diamond substrate. After cleaning and drying, a diamond with germanium vacancy color centers is obtained.

[0018] The present invention uses a patterned Ge thin film as a germanium source, creates a Ge atmosphere by etching Ge elements with hydrogen during the CVD process, and then grows diamond for a short time. Vacancies are generated during this process, and finally a single GeV color center with excellent performance is formed. Since the present invention generates vacancies on the diamond surface by growing for a short time after etching Ge elements, the finally obtained GeV color centers are also all in the subsurface layer. At the same time, germanium elements are deposited on the diamond surface by magnetron sputtering to form a thin film, and the thin film is patterned by photolithography technology, so as to achieve region-specific coating and generate GeV color centers at fixed points. Generally speaking, the present invention breaks away from the traditional preparation method of GeV color centers and can prepare shallow and locatable GeV color centers on the surface of high-temperature and high-pressure diamond.

[0019] The method for preparing diamond germanium vacancy color centers with patterned thin films in a region-specific manner based on the MPCVD method according to the present invention has the following beneficial effects:

[0020] 1. The present invention deposits a patterned germanium thin film on the diamond surface and uses the MPCVD method to prepare region-specific GeV color centers. Compared with the ion implantation method and the electron irradiation method, the process flow is simple, the equipment cost is lower, the operation is safer, and it can effectively promote the applied research based on GeV color centers.

[0021] 2. Since the thickness of the epitaxial layer is controlled to be at a relatively thin level by the growth time, the generated GeV color centers are also in a subsurface layer closer to the surface. In practical applications, it is necessary to make the GeV color centers in the shallow layer in order to obtain better luminescence efficiency. Therefore, the shallow GeV color centers generated by the present invention meet the application requirements.

[0022] 3. The current magnetron sputtering metal coating process is very mature and can reach dimensions in the order of hundreds of nanometers or even tens of nanometers, which enables the preparation of GeV color centers with a sufficiently low concentration.

[0023] 4. The maturity of photolithography technology enables the design and drawing of required patterns on diamond wafers, which makes it possible to prepare patterned thin films and further realize a GeV color center distribution with completely controllable lateral positions. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of the pattern of the patterned germanium thin film coated on the diamond surface of the present invention;

[0025] Figure 2 It is a photoluminescence spectrum diagram of the etched area in Example 1, and an obvious GeV color center signal appears in the etched area;

[0026] Figure 3 It is a fluorescence array diagram observed under a microscope in Example 1. Detailed Embodiments

[0027] Embodiment 1: The method for preparing diamond germanium vacancy color centers with patterned thin films in a fixed area based on the MPCVD method is implemented according to the following steps:

[0028] 1. Cleaning:

[0029] Ultrasonically clean the high-temperature and high-pressure diamond substrate to obtain the cleaned diamond substrate;

[0030] 2. Preparing the surface germanium distribution pattern:

[0031] a. Spin-coat photoresist uniformly on the surface of the cleaned diamond substrate, dry and cure the photoresist, then put it into a lithography machine and perform lithography according to the germanium thin film pattern. After soaking in the developer, a patterned mask is formed;

[0032] b. Deposit a germanium thin film on the patterned mask by physical vapor deposition process. After soaking and treating with a stripping solution and cleaning, a diamond substrate with a patterned germanium thin film is obtained. The patterned germanium thin film is in the form of a nanodot matrix;

[0033] 3. Etching and growth:

[0034] c. Put the diamond substrate with the patterned germanium thin film into the CVD growth chamber, close the chamber and evacuate, then introduce hydrogen to activate the plasma, increase the gas pressure and microwave power to make the temperature of the diamond substrate with the patterned germanium thin film reach 800 - 900 °C, and introduce methane for epitaxial growth to form GeV color centers;

[0035] d. After the epitaxial growth is completed, gradually reduce the gas pressure and microwave power in the CVD growth chamber, let the gas out and take out the diamond substrate. After cleaning, drying and blowing, a diamond with germanium vacancy color centers is obtained.

[0036] This embodiment can effectively reduce the preparation cost of diamond GeV color centers, and can prepare shallow and low-concentration GeV color centers in a fixed area, and is expected to be applied in local controllable and scalable coupled quantum systems.

[0037] Embodiment 2: The difference between this embodiment and Embodiment 1 is that the physical vapor deposition process in step b of step 2 is a magnetron sputtering coating process.

[0038] Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that the thickness of the germanium thin film deposited in step b of step 2 is 100 - 400 nm.

[0039] Embodiment 4: The difference between this embodiment and any one of Embodiments 1 to 3 is that the patterned germanium thin film in step b of step 2 is in the form of a nanodot matrix, the diameter of the germanium thin film dots is 5 - 10 μm, and the spacing between the germanium thin film dots is 1 - 2 μm.

[0040] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that the process of preparing the surface germanium distribution pattern in Step 2 is replaced by:

[0041] Ⅰ. Spin-coat an imprinting adhesive on the surface of the cleaned diamond substrate, place it on a hot plate for baking treatment at a temperature of 80 - 100 °C, then press the template into the imprinting adhesive, and at the same time turn on the ultraviolet light source to cure the imprinting adhesive and leave a residual layer. Peel off the template to obtain the imprinted diamond substrate;

[0042] Ⅱ. Put the imprinted diamond substrate into a RIE (Reactive Ion Etching) device, introduce oxygen for etching to remove the residual layer, and obtain a diamond substrate with a patterned mask;

[0043] Ⅲ. Deposit a germanium thin film on the diamond substrate with a patterned mask by physical vapor deposition process, then soak it in a stripping solution for treatment, and after cleaning, obtain a diamond substrate with a patterned germanium thin film. The patterned germanium thin film is in the form of a nano-dot matrix.

[0044] In Step Ⅱ of this embodiment, the residual layer of the imprinting adhesive not covered by the template is removed by oxygen etching to expose the substrate and make the pattern clearer.

[0045] Specific Embodiment 6: The difference between this embodiment and Specific Embodiment 5 is that in Step Ⅰ, the process of spin-coating the imprinting adhesive is to first rotate at a low speed of 500 rpm for 5 seconds to evenly spread the imprinting adhesive, and then rotate at a high speed of 3000 - 5000 rpm for 30 seconds.

[0046] Specific Embodiment 7: The difference between this embodiment and Specific Embodiment 5 is that in Step Ⅱ, the microwave power is controlled at 50 - 100 W, the oxygen flow rate is 20 - 50 sccm, and the etching time is 1 - 5 minutes.

[0047] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that in Step Ⅲ, hydrogen is introduced, the hydrogen flow rate is controlled at 100 - 200 sccm, the pressure in the CVD growth chamber is adjusted to 4 - 6 Torr, and the power of the microwave generator is set to 0.6 kW to activate the plasma.

[0048] Specific Embodiment 9: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that in Step Ⅲ, the pressure and microwave power are increased to make the temperature of the diamond substrate with a patterned germanium thin film reach 800 - 900 °C, methane is introduced, the volume concentration of methane is controlled at 2% - 3%, and epitaxial growth is carried out to form GeV color centers.

[0049] Specific Embodiment 10: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that in Step Ⅲ, the epitaxial growth time is 1.5 - 2.5 h.

[0050] Example 1: The method for preparing diamond germanium vacancy color centers in a patterned thin film in a defined area based on the MPCVD method is implemented according to the following steps:

[0051] 1. Cleaning:

[0052] The high-temperature and high-pressure diamond substrate is ultrasonically cleaned successively with acetone, deionized water, and absolute ethanol. The power of each ultrasonic cleaning is 100 W, and the cleaning time is 30 min. After drying, the cleaned diamond substrate is obtained;

[0053] 2. Preparing a surface germanium distribution pattern:

[0054] a. Drop photoresist on the surface of the cleaned diamond substrate, adjust the rotation speed to 2000 rpm and rotate for 30 seconds, then rotate at a high speed of 8000 rpm for 60 seconds to make the photoresist spin-coated evenly. Place it on a heating table and bake at 95 °C for 90 seconds to cure the photoresist. Then put it into a lithography machine and perform lithography according to the germanium thin film pattern (as Figure 1 shown). After soaking in the developer for 60 seconds, a patterned mask is formed;

[0055] b. Deposit a germanium thin film on the patterned mask using a magnetron sputtering deposition process. The magnetron sputtering process is as follows: evacuate to 5×10 -4 Pa, then introduce argon. Adjust the gate valve, adjust the argon gas pressure to 5 Pa, then turn on the radio frequency power supply to input 60 W of energy for plasma ignition. After ignition, adjust the argon gas pressure to 0.5 Pa, open the baffle to start deposition. After deposition, soak in the stripping solution for 2 hours, use a wash bottle pump to impact the sample surface with deionized water, and peel off the excess germanium thin film to obtain a diamond substrate with a patterned germanium thin film. The patterned germanium thin film is in a micron dot matrix. The diameter of the germanium thin film dots is 5 μm, the spacing between the germanium thin film dots is 1 μm, and the thickness of the germanium thin film is 220 nm;

[0056] 3. Etching and growth:

[0057] c. Put the diamond substrate with the patterned germanium thin film into the CVD growth chamber. After closing the chamber, evacuate to make the chamber pressure reach 1.0×10 -1 Torr, then introduce hydrogen with a flow rate of 100 sccm, adjust the chamber pressure to 5 Torr, start the microwave generator with an initial power of 0.6 kW to activate the plasma, and increase the pressure and power simultaneously according to the rule that for every 0.1 kW increase in power, the pressure increases by 3 Torr, so that the surface temperature of the diamond substrate reaches 850 °C. Introduce methane, control the hydrogen flow rate to 498 sccm, and the methane flow rate to 2 sccm, and perform epitaxial growth for 2 h to form GeV color centers;

[0058] d. After the epitaxial growth is completed, gradually reduce the gas pressure and microwave power in the CVD growth chamber, close the valves of hydrogen and methane as well as the main inlet valve, and turn off the power supply of the microwave generator. Pump the gas to 1.0×10 -1 Torr, then vent to atmospheric pressure, open the chamber door, and after cleaning and drying, obtain diamond with germanium vacancy color centers.

[0059] In this embodiment, photoluminescence spectroscopy characterization is performed on the diamond with germanium vacancy color centers:

[0060] (1) Use a 10× microscope to focus on the etched pits on the diamond to determine the characterization area.

[0061] (2) Switch to a 50× microscope for observation, select the test points, and refocus.

[0062] (3) Use an excitation light source of 532 nm excitation light, with an energy of 2 mW, a scanning time of 1 s, adjust the test spectral range to 550 - 650 nm, and measure the fluorescence spectrum at the selected area points.

[0063] (4) Compare the spectra with the uncoated germanium area, that is, the unetched area. It is found that only the GeV color center signal appears in the etched area, while only the Raman characteristic peak signal of diamond appears in the unetched area, without the GeV color center signal. As Figure 2 shown. This indicates that the GeV color center is successfully prepared by this method.

[0064] In this embodiment, fluorescence array observation is performed on the diamond with germanium vacancy color centers:

[0065] Place the sample under an optical microscope, adjust to 50×, observe the fluorescence array and save the luminescence pictures. As Figure 3 shown, Figure 3 visually display the fluorescence array, indicating that the GeV single - photon source array is successfully prepared.

[0066] The density of the GeV color centers prepared in this embodiment is approximately 1 - 2 fluorescence centers in a region of 10 μm×10 μm.

[0067] Example 2: The difference between this example and Example 1 is in step two for preparing the surface germanium distribution pattern:

[0068] Ⅰ. Spin - coat ultraviolet nano - curable glue on the surface of the cleaned diamond substrate, rotate at a low speed of 500 rpm for 5 s to evenly spread the imprinting glue, then rotate at a high speed of 4000 rpm for 30 s, bake it on a hot plate at a temperature of 100 °C for 1 minute, then press the template into the imprinting glue, apply a uniform pressure of 10 bar, and at the same time turn on the ultraviolet light source with a wavelength of 365 nm to cure the imprinting glue, peel off the template, and use an optical microscope to check the pattern quality to ensure no defects, thus obtaining the imprinted diamond substrate;

[0069] II. Place the imprinted diamond substrate into a RIE (Reactive Ion Etching) device, introduce oxygen for etching to remove the residual layer, and transfer the pattern to the diamond surface. The etching parameters are: power 75 W, gas flow rate 20 sccm, and time 2 minutes, to obtain a diamond substrate with a patterned mask.

[0070] III. Deposit a germanium thin film on the diamond substrate with a patterned mask using physical vapor deposition technology, then soak it in a stripping solution for 2 hours, and after cleaning, obtain a diamond substrate with a patterned germanium thin film. The patterned germanium thin film is in the form of a micron dot matrix.

[0071] The present invention provides an innovative, low-cost, and simple preparation method for point defect luminescence centers widely existing in fields such as basic physical research and materials science. At the same time, it provides technical support for key technical engineering fields such as single-photon sources, quantum antennas, and quantum communication of diamond-based GeV color centers.

Claims

1. A method for preparing diamond germanium vacancy color centers in a fixed area of ​​a patterned thin film based on MPCVD, characterized in that The method for preparing diamond germanium vacancy color center is achieved by the following steps:

1. Cleaning: Ultrasonic cleaning is performed on the high temperature and high pressure diamond substrate to obtain a cleaned diamond substrate; 2. Preparation of surface germanium distribution pattern: a. Spin-coat the cleaned diamond substrate surface with photoresist uniformly, dry and solidify the photoresist, then place it in a photolithography machine, perform photolithography according to the germanium film pattern, and form a patterned mask after soaking in a developer; b. Depositing a germanium film on the patterned mask by physical vapor deposition, soaking in a degumming solution, and washing to obtain a diamond substrate with a patterned germanium film, wherein the patterned germanium film is a nano-dot matrix; 3. Etching and growth: c. Place the diamond substrate with the patterned germanium film in the CVD growth chamber, close the chamber and evacuate it, then introduce hydrogen to activate the plasma, increase the gas pressure and microwave power, so that the temperature of the diamond substrate with the patterned germanium film reaches 800-900°C, introduce methane for epitaxial growth and form GeV color centers; d. After the epitaxial growth is completed, the gas pressure and microwave power in the CVD growth chamber are gradually reduced, the diamond substrate is taken out after venting, and the diamond with germanium vacancy color center is obtained after cleaning and drying.

2. The method for preparing diamond germanium vacancy color centers in a fixed area of ​​a patterned thin film based on MPCVD according to claim 1, characterized in that The physical vapor deposition process described in step b of step two is a magnetron sputtering coating process.

3. The method for preparing diamond germanium vacancy color centers in a fixed area of ​​a patterned thin film based on MPCVD method according to claim 1, characterized in that The thickness of the germanium film deposited in step b of step 2 is 100-400 nm.

4. The method for preparing diamond germanium vacancy color centers in a fixed area of ​​a patterned thin film based on MPCVD method according to claim 1, characterized in that In step b of step 2, the patterned germanium film is in a nano dot matrix, the diameter of the germanium film dots is 5 to 10 μm, and the spacing between the germanium film dots is 1 to 2 μm.

5. The method for preparing diamond germanium vacancy color centers in a fixed area of ​​a patterned thin film based on MPCVD method according to claim 1, characterized in that The process of preparing the surface germanium distribution pattern in step 2 is replaced by: Ⅰ. Spin-coat the imprint glue on the surface of the cleaned diamond substrate, place it on a hot plate and bake it at a temperature of 80-100°C, then press the template into the imprint glue, turn on the ultraviolet light source at the same time to solidify the imprint glue and leave a residual layer, peel off the template, and obtain the imprinted diamond substrate; II. Place the imprinted diamond substrate into the RIE equipment, introduce oxygen to etch away the residual layer, and obtain a diamond substrate with a patterned mask; III. A germanium film is deposited on a diamond substrate with a patterned mask by using a physical vapor deposition process, and then immersed in a degumming solution. After cleaning, a diamond substrate with a patterned germanium film is obtained, and the patterned germanium film is in a nano-dot matrix.

6. The method for preparing diamond germanium vacancy color centers in a fixed area of ​​a patterned thin film based on MPCVD method according to claim 5, characterized in that In step I, the process of spin coating the embossing adhesive is to first spin at a low speed of 500 rpm for 5 seconds to spread the embossing adhesive evenly, and then spin at a high speed of 3000-5000 rpm for 30 seconds.

7. The method for preparing diamond germanium vacancy color centers in a fixed area of ​​a patterned thin film based on MPCVD according to claim 5, characterized in that In step II, the microwave power is controlled to be 50-100 W, the oxygen flow rate is 20-50 sccm, and the etching time is 1-5 minutes.

8. The method for preparing diamond germanium vacancy color centers in a fixed area of ​​a patterned thin film based on MPCVD method according to claim 1, characterized in that In step 3, hydrogen is introduced, and the hydrogen flow rate is controlled to be 100-200 sccm, the gas pressure in the CVD growth chamber is adjusted to 4-6 Torr, and the power of the microwave generator is set to 0.6 kW to activate the plasma.

9. The method for preparing diamond germanium vacancy color centers in a fixed area of ​​a patterned thin film based on MPCVD method according to claim 1, characterized in that In step three, the gas pressure and microwave power are increased to make the temperature of the diamond substrate with the patterned germanium film reach 800-900° C., and methane is introduced to control the volume concentration of methane to 2%-3% to perform epitaxial growth and form GeV color centers.

10. The method for preparing diamond germanium vacancy color centers in a fixed area of ​​a patterned thin film based on MPCVD method according to claim 9, characterized in that The epitaxial growth time in step three is 1.5 to 2.5 hours.

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