Nanocrystalline diamond film grown by pulsed linear antenna microwave CVD

• Published in: Diamond and related materials Vol. 119; p. 108576
• Main Authors: Gu, Jiteng, Chen, Zhongxin, Li, Runlai, Zhao, Xiaoxu, Das, Chandan, Sahmuganathan, Vicknesh, Sudijono, John, Lin, Ming, Loh, Kian Ping
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2021; Elsevier BV
• Subjects: Actuators; Antennas; Continuous plasma; Diamond films; Gas mixtures; Hardness; Linear antenna plasma deposition (LAPD); Nanocrystalline diamond film; Nanocrystals; Payloads; Plasma; Plasma deposition; Pulsed plasma; Residual stress; Smooth film; Smoothness; Substrates; Tribology; Pulsed plasma; Smooth film; Continuous plasma; Residual stress; Nanocrystalline diamond film; Linear antenna plasma deposition (LAPD)
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2021.108576

The growth of large area nanocrystalline diamond (NCD) films is of industrial interests because of their applications as tribological coatings and micromechanical actuators. To reduce thermal payloads, pulsed linear antenna plasma deposition (LAPD) has been developed to grow NCD at a lower average substrate temperature than continuous plasma deposition, but the relationship between pulse cycles and film microstructure is not well understood. Here, we investigated the pulsed LAPD growth of smooth nanocrystalline diamond with high hardness and low residual stress on 4-inch wafers, carried out at 500 °C substrate temperature using CH4/CO2/H2 gas mixtures. By alternating continuous and pulsed plasma, smooth film with a hardness of 38 GPa, modulus of 315 GPa and residual stress of −690 MPa was grown. TEM cross-section analysis of the interface provided insights into the film morphology as a function of pulsed deposition conditions. Our work shows that frequency-modulated plasma allows the growth of nanocrstalline diamond films with desirable attributes of smoothness, high mechanical strength and low residual stress. [Display omitted] •Linear antenna plasma deposition of 4-inch nanocrystalline diamond wafer•Cross-sectional TEM study of nanocrystalline diamond films grown by pulsed plasma•Correlation between surface morphology and microstructure•Film stress control by multi-cycle continuous-pulsed plasma