Preparation of High-Concentration Diamond Vacancy Color Centers by Microwave Plasma Chemical Vapor Deposition and Their Performance Study

Preparation of High-Concentration Diamond Vacancy Color Centers by Microwave Plasma Chemical Vapor Deposition and Their Performance Study

Preparation of High-Concentration Diamond Vacancy Color Centers

• Preparation Principle
• Microwave Plasma Chemical Vapor Deposition (MPCVD) technology uses microwave energy to excite the reaction gases (such as methane, hydrogen, and nitrogen) to dissociate them into active groups, such as H, O, N atoms, or CH₂, CH₃, C₂H₂, etc. These active groups deposit on the diamond substrate surface to form diamond crystals.
• By doping different concentrations of nitrogen atoms in the precursor gases, high concentrations of nitrogen impurities can be introduced into the diamond, thereby creating high-concentration nitrogen-vacancy (NV) color centers.
• Preparation Process
• Substrate Preparation: The cleaned diamond substrate is placed into the MPCVD chamber, which is then sealed and evacuated.
• Gas Injection and Reaction: Methane, hydrogen, and nitrogen reaction gases are introduced. The microwave energy excites the gas molecules to produce a high concentration of plasma.
• Crystal Growth: Under suitable pressure and temperature conditions, diamond crystals gradually grow. By precisely controlling the growth parameters (such as growth time, pressure, microwave power, etc.), the size and quality of the diamond particles can be accurately controlled.
• Post-Processing: High-nitrogen diamond single crystals are subjected to electron irradiation, which can significantly increase the concentration of diamond NV color centers.

Performance Study of High-Concentration Diamond Vacancy Color Centers

• Optical Properties
• Diamonds with high-concentration NV color centers exhibit good optical properties, and their fluorescence characteristics can be enhanced by different oxidation methods and annealing treatments. For example, air annealing can enhance the fluorescence of silicon-vacancy (SiV) color centers.
• Quantum Magnetic Detection Performance
• NV color centers have the advantages of good stability at room temperature and long electron spin coherence time, which can be manipulated by laser and microwave. After electron irradiation treatment, diamonds with high-concentration NV color centers show excellent performance in quantum magnetic detection.
• Structure and Defects
• Under high-nitrogen conditions, nitrogen atoms in diamond single crystals mainly exist in the form of aggregated nitrogen and single substitutional N⁺. Different oxidation methods have a significant impact on the structural evolution of nanodiamond films.

Research Progress and Applications

• Research Progress
• In recent years, significant progress has been made in the preparation of diamond NV color centers using MPCVD. For example, Zhongnan Diamond Co., Ltd., and the 13th Research Institute of China Electronics Technology Group Corporation have successfully prepared diamond single crystals with high-concentration NV color centers using MPCVD and verified their quantum magnetic detection performance.
• Application Prospects
• Diamonds with high-concentration NV color centers have broad application prospects in the fields of quantum computing, quantum sensing, and magnetic field detection. Their excellent optical and quantum magnetic detection properties make them an important material in the field of quantum technology.