| Metadata | Details |
|---|
| Publication Date | 2024-03-12 |
| Journal | Materials |
| Authors | Ying Ren, Wei Lv, Xiaogang Li, Haoyong Dong, Nicolas Wöhrl |
| Institutions | Shenzhen Institutes of Advanced Technology, Henan University of Technology |
| Citations | 8 |
| Analysis | Full AI Review Included |
- Accelerated Growth Rate: The introduction of nitrogen (N2) into the MPCVD gas mixture increased the single-crystal diamond (SCD) growth rate by a factor of 4.5, rising from 10 ”m/h (undoped) to a maximum of 45.5 ”m/h.
- Optimal Doping Level: The highest growth rate was achieved at an N2/H2 concentration of 1.2%, with the rate diminishing at higher concentrations (1.5%).
- NV Center Mechanism: The enhanced growth rate correlates synchronously with the concentration of Nitrogen-Vacancy (NV) defects, suggesting that NV center formation activates the diamond lattice and facilitates the incorporation of growth species.
- Morphological Shift: N2 addition altered the growth mode from the desirable step-flow to bi-dimensional nucleation, resulting in clustered steps, rougher surfaces, and the formation of macroscopically pyramidal hillocks.
- Crystalline Quality: Raman analysis showed that despite the introduction of compressive stress and the formation of non-diamond sp2 C-C bonds (confirmed by XPS) at higher doping levels, the overall crystalline quality remained high (Raman FWHM 3.1-4.1 cm-1).
- Bonding Confirmation: XPS confirmed the presence of C-N bonds and the emergence of non-diamond carbon phases (sp2 C-C) upon N2 doping, consistent with the observed morphological changes.
| Parameter | Value | Unit | Context |
|---|
| Maximum SCD Growth Rate | 45.5 | ”m/h | Achieved at 1.2% N2/H2 doping (Sample S4) |
| Growth Rate Enhancement | 4.5 | Factor | Compared to undoped SCD (10 ”m/h) |
| Optimal N2/H2 Ratio | 0.8 to 1.2 | % | Range for stabilized maximum growth rate |
| Microwave Frequency | 2.45 | GHz | MPCVD system specification |
| Plasma Power | ~3.25 | kW | Fixed operating condition |
| Substrate Temperature | ~950 | °C | Fixed operating condition |
| Operating Pressure | ~13 | kPa | Fixed operating condition |
| H2 Flow Rate | 300 | sccm | Fixed flow rate |
| CH4 Flow Rate | 24 | sccm | Fixed flow rate |
| Diamond Raman Peak | 1332 | cm-1 | Intrinsic zone center phonon band |
| Raman FWHM Range | 3.1 to 4.1 | cm-1 | Across all N2 doping levels (S0-S5) |
| NV0 ZPL Emission | 575 | nm | Neutral Nitrogen-Vacancy center |
| NV- ZPL Emission | 637 | nm | Negatively charged Nitrogen-Vacancy center |
| XPS sp3 C-C Peak | ~285 | eV | Characteristic diamond lattice bonding |
| XPS sp2 C-C Peak | ~284.4 | eV | Non-diamond carbon phase (observed with N2) |
- Substrate Preparation: High-temperature, high-pressure (HPHT) Ib (100) SCDs (3.8 x 3.8 x 1 mm3) were used as seed crystals. Seeds underwent ultrasonic cleaning followed by 30 minutes of H2 plasma etching (12 kPa) for surface defect removal.
- MPCVD Synthesis: Growth was performed using a 5 kW, 2.45 GHz Microwave Plasma Chemical Vapor Deposition system for four hours per sample.
- Gas Mixture Control: H2 and CH4 flows were fixed at 300 sccm and 24 sccm, respectively. N2 flow was systematically varied (0 to 4.5 sccm) to achieve N2/H2 doping ratios from 0% to 1.5%.
- Growth Conditions: Standardized parameters included a substrate temperature of ~950 °C, plasma power of ~3.25 kW, and pressure of ~13 kPa.
- Morphology Characterization: Raman confocal microscopy and pinhole three-dimensional confocal methods were used to observe the transition from step-flow growth (undoped) to bi-dimensional nucleation (N2-doped).
- Crystalline and Defect Analysis (Raman/PL):
- Raman spectroscopy measured the 1332 cm-1 peak and FWHM to assess crystalline quality and internal stress.
- Photoluminescence (PL) spectroscopy identified and quantified NV centers (NV0 at 575 nm and NV- at 637 nm), demonstrating a correlation between NV concentration and growth rate.
- Bonding Structure Analysis (XPS): X-ray Photoelectron Spectroscopy (XPS) was used to analyze the C1s and N1s core levels, confirming the presence of C-N bonds and the formation of non-diamond sp2 C-C phases at higher N2 concentrations.
- Quantum Technology: The controlled, high-rate generation of NV centers (NV- and NV0) is essential for producing diamond substrates used in quantum sensing (e.g., magnetometers, thermometers) and solid-state quantum computing applications.
- High-Power RF Devices: The ability to grow thick, high-quality SCDs rapidly supports the fabrication of diamond heat spreaders for GaN-based high-electron-mobility transistors (HEMTs), critical for 5G/6G infrastructure and radar systems.
- Advanced Optics: High-rate CVD growth enables the cost-effective production of large-area, high-purity diamond windows and lenses for high-power laser systems, where low absorption and high thermal stability are mandatory.
- Thermal Management: SCDs grown at 45 ”m/h can be scaled up to provide superior thermal dissipation solutions for complex microelectronic packages and high-density integrated circuits.
- Semiconductor Substrates: The enhanced growth kinetics facilitate the production of large, high-quality SCD substrates necessary for next-generation diamond-based semiconductor devices (e.g., diodes, transistors) that operate under extreme conditions.
View Original Abstract
Concurrently achieving high growth rate and high quality in single-crystal diamonds (SCDs) is significantly challenging. The growth rate of SCDs synthesized by microwave plasma chemical vapor deposition (MPCVD) was enhanced by introducing N2 into the typical CH4-H2 gas mixtures. The impact of nitrogen vacancy (NV) center concentration on growth rate, surface morphology, and lattice binding structure was investigated. The SCDs were characterized through Raman spectroscopy, photoluminescence (PL) spectroscopy, and X-ray photoelectron spectroscopy. It was found that the saturation growth rate was increased up to 45 ÎŒm/h by incorporating 0.8-1.2% N2 into the gas atmosphere, which is 4.5 times higher than the case without nitrogen addition. Nitrogen addition altered the growth mode from step-flow to bidimensional nucleation, leading to clustered steps and a rough surface morphology, followed by macroscopically pyramidal hillock formation. The elevation of nitrogen content results in a simultaneous escalation of internal stress and defects. XPS analysis confirmed chemical bonding between nitrogen and carbon, as well as non-diamond carbon phase formation at 0.8% of nitrogen doping. Furthermore, the emission intensity of NV-related defects from PL spectra changed synchronously with N2 concentrations (0-1.5%) during diamond growth, indicating that the formation of NV centers activated the diamond lattice and facilitated nitrogen incorporation into it, thereby accelerating chemical reaction rates for achieving high-growth-rate SCDs.
- 2019 - Conductive diamond: Synthesis, properties, and electrochemical applications [Crossref]
- 2021 - Progress in semiconductor diamond photodetectors and MEMS sensors [Crossref]
- 2021 - Diamond as the heat spreader for the thermal dissipation of GaN-based electronic devices [Crossref]
- 2004 - Homoepitaxial diamond growth by high-power microwave-plasma chemical vapor deposition [Crossref]
- 2005 - High rate growth and electrical/optical properties of high-quality homoepitaxial diamond (100) films [Crossref]
- 2002 - Very high growth rate chemical vapor deposition of single-crystal diamond [Crossref]
- 2004 - The effect of nitrogen addition during high-rate homoepitaxial growth of diamond by microwave plasma CVD [Crossref]
- 1996 - Influence of nitrogen additions on hot-filament chemical vapor deposition of diamond [Crossref]
- 2016 - Spectroscopic studies of yellow nitrogen-doped CVD diamonds [Crossref]
- 2009 - Enhanced growth of high quality single crystal diamond by microwave plasma assisted chemical vapor deposition at high gas pressures [Crossref]