Epitaxial growth method of shallow diamond quantum sensor for in-situ impurity regulation and control

Abstract

The invention relates to an epitaxial growth method of a shallow diamond quantum sensor with in-situ impurity regulation and control, which belongs to the technical field of semiconductor material growth and application, realizes efficient removal of in-situ nitrogen and silicon impurities by introducing transition metal in the growth process, and realizes preparation of a shallow NV color center by combining a short-time secondary growth technology. The method comprises the specific steps of polishing and cleaning a substrate, growing a high-quality diamond epitaxial layer, growing a nitrogen-doped thin-layer diamond and the like. According to the method, the non-toxic, volatile and cheap metal source solution is selected and loaded into the MPCVD cavity through hydrogen or metal particles are placed in situ, so that in-situ removal of impurities such as nitrogen and silicon is achieved. And a new scheme is provided for preparing the SCD meeting the application requirements of semiconductor devices, quantum devices and optical devices. Meanwhile, the method using the transition metal source has the advantages of low cost and good effect, and is beneficial to large-area development.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor material growth and application, and specifically relates to a method for epitaxial growth of a diamond single crystal shallow diamond quantum sensor, and particularly relates to a method for growing a high-purity diamond single crystal. Background Art

[0002] The NV color center in diamond is a lattice defect structure formed by a nitrogen atom replacing a carbon atom in the diamond lattice and forming a lattice defect structure with the adjacent carbon vacancy. The NV color center has the following characteristics along the connection direction of "nitrogen atom-vacancy": Symmetry (NV center axial orientation). Compared to defects in other materials, NV centers offer advantages such as excellent room-temperature quantum properties, long coherence times, and compatibility with micro- and nanofabrication, making them a new direction for the development of chip-based high-precision sensor technology. Currently, they have been widely used to measure a variety of physical quantities, including magnetic fields, electric fields, temperature, and angular velocity, with increasing application in aerospace, deep space exploration, and life sciences. NV centers exist in natural and synthetic diamonds. However, these naturally formed NV centers are randomly distributed within diamond, limiting their practical applications. Typically, relatively high NV concentrations are required to improve sensitivity and signal-to-noise ratio. However, this approach inevitably shortens the spin coherence time of the NV center. Furthermore, many high-sensitivity or nanoscale sensing applications require shallow NV centers because the magnetic dipole coupling between the sensor and the analyte is inversely proportional to the cube of the distance. In recent years, various methods have been developed to achieve high-performance NV centers. High-temperature annealing after N ion implantation can produce high-density and well-aligned NV ensembles in specific regions, and the depth of the NV center can be regulated by controlling the ion implantation energy. However, high-energy ions can cause a large amount of lattice damage and paramagnetic defects, affecting the optical and quantum properties of the color centers. High-energy electron irradiation can also produce NV ensembles in diamond. The required lateral and vertical resolution can be achieved by controlling the irradiation conditions, but the focused electron beam limits the irradiation area and efficiency and causes lattice damage. The chemical vapor deposition (CVD) method can accurately introduce nitrogen during the diamond growth process, which is conducive to controlling the doping concentration and spatial position. Compared with the ion implantation method, the obtained NV color centers have better quantum properties such as coherence time. However, in order to achieve shallow color centers, whether it is ion implantation or CVD method, nitrogen-free diamond material must be selected as the substrate.

[0003] Nitrogen impurities are often detected in diamond epitaxial materials due to chamber leaks and inherent gas purity. Nitrogen replaces carbon atoms and combines with adjacent vacancies to form NV color centers. Furthermore, nitrogen impurities introduce additional energy levels into the diamond band gap. Consequently, nitrogen impurities have a multifaceted impact on the optical properties of diamond, such as altering crystal color, trapping / recombining photogenerated carriers, and reducing optical transmittance. Common approaches to reducing impurity concentrations include interconnecting multiple vacuum chambers, increasing hydrogen flow rates, or improving chamber structure. However, these processes are complex, costly, or inefficient. Currently, approaches to suppress nitrogen impurities in MPCVD diamond growth focus on four key strategies: adjusting growth parameters, minimizing gas leaks, specialized substrate design, introducing oxygen additives, and utilizing tungsten-nitrogen co-doping. However, these approaches face practical limitations due to expensive equipment requirements, inconsistent process reproducibility, and highly toxic metal additives. In high-temperature, high-pressure systems, titanium (Ti) powder acts as an effective nitrogen getter by forming Ti-N inclusions, thereby reducing nitrogen incorporation and inducing a color shift from yellow to colorless. However, inclusions can leave residual amounts within the sample, affecting the sample's crystallization quality. Furthermore, this strategy fails in MPCVD processes due to Ti's high melting point (~1668°C), which hinders its activation under typical MPCVD conditions (typically <1000°C). Consequently, diamond substrates with nitrogen impurity concentrations as low as ppb are currently expensive and small in size. Summary of the Invention

[0004] The main purpose of the present invention is to overcome the shortcomings of the background technology, and to use hydrogen as a carrier gas to bring a non-toxic, inexpensive transition metal solution into the MPCVD chamber or to place transition metal particles in situ to remove nitrogen impurities in the growth environment. Obvious nitrogen and silicon color center PL peaks can be observed in the epitaxial material obtained under conventional growth conditions, and the luminescence peak intensity related to these impurities is significantly suppressed as the transition metal solution source flow rate or the number of particles increases. Based on this scheme, the silicon and nitrogen impurities in the epitaxial material can be reduced to the spectral detection limit. On the basis of this high-purity substrate, the present invention can realize a thin nitrogen-containing epitaxial layer by regulating the nitrogen content in the growth atmosphere, and realize a shallow NV color center with controllable concentration.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for epitaxial growth of shallow diamond quantum sensors with in-situ impurity regulation is described. This method introduces transition metals during the growth process to achieve efficient in-situ removal of nitrogen and silicon impurities, and combines short-time secondary growth technology to achieve the preparation of shallow NV color centers. The method specifically includes the following steps:

[0007] S1. Select high-quality single-crystal diamond material as substrate 1 and polish and clean it before growth;

[0008] S2. Using a CVD method to grow a high-quality diamond epitaxial layer 2 on a single crystal diamond substrate. Unlike conventional growth processes, transition metal particles are placed on the edge of the substrate or a transition metal solution source is added during the growth of the high-quality layer.

[0009] S3, secondary growth of a nitrogen-doped thin layer of diamond 3 on the surface of the diamond epitaxial layer (2); obtaining a shallow diamond quantum sensor.

[0010] Preferably, the high-quality single crystal diamond material in step S1 is any one of natural diamond, spliced-grown or heteroepitaxially grown diamond self-supporting substrate, with a thickness of 10 nm to 10 mm and a surface roughness of the order of nm after polishing.

[0011] Preferably, the thickness of the high-quality diamond epitaxial layer 2 grown in step S2 is 10 nm to 10 mm. The SCD deposition process employs direct etching of transition metal (Fe, Co, Ni, Ti, etc.) particles or the addition of a transition metal organic solution via a bubbling method. The transition metal reacts with nitrogen-related groups in the plasma to form refractory nitrides, which are then extracted from the cavity along with the gas flow.

[0012] Preferably, in step S2, if the direct etching method of transition metal particles is used, the diameter of the transition metal particles is 1 mm-5 mm, the length is 1 mm-20 mm, and the number of added particles is 1-10; if the bubbling method is used, the solute of the organic source solution used is an organic precursor based on metals such as nickel, iron, and cobalt, the solvent of the solution can be ethanol, acetone, and other liquids with certain volatility, the concentration of the organic source solution is 0.001 mol / L-5 mol / L, and the carrier gas of the bubbling method can be hydrogen, oxygen, methane, nitrogen, argon, and other gases used for CVD growth, and the gas flow rate is 5-500 sccm.

[0013] Preferably, high microwave power and high growth pressure are used in step S2 to achieve high-speed and high-quality growth of the epitaxial diamond layer. The microwave power is 2-4 kW, the growth pressure is 10-20 kPa, the hydrogen flow rate is 300-800 sccm, and the methane concentration is between 2-8%.

[0014] Preferably, the thickness of the nitrogen-doped thin diamond layer 3 grown in step S3 is 1 nm to 1 mm, and the nitrogen doping concentration is 1 ppb to 100 ppm.

[0015] Beneficial effects:

[0016] This application innovatively uses a non-toxic, volatile, and inexpensive metal source solution to remove impurities such as nitrogen and silicon in situ, either by loading hydrogen into the MPCVD chamber or by placing metal particles in situ. This provides a new approach for preparing SCDs that meet the application requirements of semiconductor devices, quantum devices, and optical devices. Furthermore, the use of transition metal sources offers the advantages of low cost and high efficacy, making it suitable for large-scale deployment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the epitaxial structure growth process of the present invention.

[0018] Figure 2 Schematic diagram of fluorescence spectra before and after the growth of SCD grown by direct etching of transition metal particles according to an embodiment of the present invention.

[0019] Figure 3 Schematic diagram of fluorescence spectra of SCD grown by bubbling transition metal organic source solution before and after growth according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described in conjunction with the embodiments, but is not limited in any way. Without departing from the technical solution of the present invention, any changes or modifications to the present invention that are easily implemented by a person of ordinary skill in the art will fall within the scope of the claims of the present invention.

[0021] Example 1:

[0022] (1) The SCD substrate, which had been pre-treated by simple polishing and acetone and ethanol cleaning, was placed in a microwave plasma chemical vapor deposition system. At the same time, nickel particles were placed around the substrate. The diameter, length, and number of the nickel particles were 3 mm, 5 mm, and 2, respectively. The input power was maintained at 2.0 kW, the reaction chamber pressure was 10 kPa, the substrate temperature was 900 ° C, and the ratio of methane to hydrogen was 3:100. The epitaxial growth of high-purity SCD with a nitrogen color center peak below the detection limit of the fluorescence spectrum was obtained, as shown in FIG. Figure 2 Finally, a thin nitrogen layer is grown by combining chamber leakage or adding nitrogen. The input power is 2.0 kW, the reaction chamber pressure is 10 kPa, the substrate temperature is 900°C, the methane to hydrogen ratio is 3:100, and the nitrogen flow rate is 0-10 sccm.

[0023] Example 2:

[0024] (1) The SCD substrate, which had been pre-treated by simple polishing and acetone and ethanol cleaning, was placed in a microwave plasma chemical vapor deposition system. The flow rate of the carrier gas in the nickel acetate ethanol solution bubbling bottle and the concentration of the solution were controlled to be 20 sccm and 0.005 mol / L, respectively. The input power was maintained at 3.0 kW, the reaction chamber pressure was 15 kPa, the substrate temperature was 950 ° C, and the ratio of methane to hydrogen was 3:100. Finally, the epitaxial growth of high-purity SCD with a nitrogen color center peak below the detection limit of the fluorescence spectrum was obtained. Figure 3 Finally, a thin nitrogen layer is grown by combining chamber leakage or adding nitrogen. The input power is 2.0 kW, the reaction chamber pressure is 10 kPa, the substrate temperature is 900°C, the methane to hydrogen ratio is 3:100, and the nitrogen flow rate is 0-10 sccm.

Claims

1. A method for epitaxial growth of shallow diamond quantum sensors with in-situ impurity regulation. This method introduces transition metals during the growth process to achieve efficient in-situ removal of nitrogen and silicon impurities, and combines short-time secondary growth technology to achieve the preparation of shallow NV color centers. The method specifically includes the following steps: S1. Selecting high-quality single-crystal diamond material as a substrate (1), and polishing and cleaning the substrate before growth; S2. growing a high-quality diamond epitaxial layer (2) on a single crystal diamond substrate using a CVD method. Unlike conventional growth processes, transition metal particles are placed on the edge of the substrate or a transition metal solution source is added when growing the high-quality layer. S3. Secondarily growing a nitrogen-doped thin layer of diamond (3) on the surface of the diamond epitaxial layer (2); obtaining a shallow diamond quantum sensor.

2. The epitaxial growth method of a shallow diamond quantum sensor controlled by in-situ impurities according to claim 1, characterized in that: The high-quality single crystal diamond material described in step S1 is any one of natural diamond, spliced growth or heteroepitaxial growth diamond self-supporting substrate, with a thickness of 10nm to 10mm and a surface roughness of the order of nm after polishing.

3. The epitaxial growth method of a shallow diamond quantum sensor controlled by in-situ impurities according to claim 1, characterized in that: The thickness of the high-quality diamond epitaxial layer (2) grown in step S2 is 10nm to 10mm. During the SCD deposition process, a transition metal particle direct etching method or a transition metal organic solution is added by a bubbling method to carry gas. The transition metal reacts with nitrogen-related groups in the plasma to form a refractory nitride, which is extracted from the cavity along with the gas flow; the transition metal is selected from Fe, Co, Ni or Ti.

4. The epitaxial growth method of a shallow diamond quantum sensor controlled by in-situ impurities according to claim 1, characterized in that: In step S2, if the direct etching method of transition metal particles is used, the diameter of the transition metal particles is 1 mm-5 mm, the length is 1 mm-20 mm, and the number of added particles is 1-10; if the bubbling method is used, the solute of the organic source solution used is an organic precursor based on nickel, iron, cobalt or titanium metal, the solvent of the solution is ethanol or acetone, the concentration of the organic source solution is 0.001 mol / L-5 mol / L, and the carrier gas of the bubbling method is hydrogen, oxygen, methane, nitrogen or argon, and the gas flow rate is 5-500 sccm.

5. The epitaxial growth method of a shallow diamond quantum sensor controlled by in-situ impurities according to claim 1, characterized in that: In step S2, high microwave power and high growth pressure are used to achieve high-speed and high-quality growth of the epitaxial diamond layer. The microwave power is 2-4 kW, the growth pressure is 10-20 kPa, the hydrogen flow rate is 300-800 sccm, and the methane concentration is between 2-8%.

6. The epitaxial growth method of a shallow diamond quantum sensor controlled by in-situ impurities according to claim 1, characterized in that: The thickness of the nitrogen-doped thin diamond (3) grown in step S3 is 1 nm to 1 mm, and the nitrogen doping concentration is 1 ppb to 100 ppm.

Images