Friction force microscopy study of diamond films modified by a glow discharge treatment |
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| Affiliation: | 1. School of Engineering and Technology, China University of Geosciences (Beijing), Beijing 100083, China;2. State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;1. CCET, Universidade de Caxias do Sul, Caxias do Sul 95070-560, Brazil;2. Departamento de Física, PUC-Rio, Rio de Janeiro 22453-900, Brazil;3. IF, Universidade Federal do Rio Grande do Sul, Porto Alegre 91509-970, Brazil;4. IFGW-DFA, Universidade Estadual de Campinas, Campinas 13083-970, Brazil;5. Plasmar Tecnologia Ltda., Caxias do Sul 95076-420, Brazil;1. Research Institute of Surface Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China;2. Shanxi Key Laboratory of Material Strength and Structure Impact, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China;3. Department of Chemical and Materials Engineering, University of Alberta, Edmonton T6G 1H9, Alberta, Canada;4. College of Electrical and Power Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China;5. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, Gansu, China;6. School of Mechanical Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, Shanxi, China;7. Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi''an Jiaotong University, Xi''an 710049, Shaanxi, China |
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| Abstract: | A glow discharge treatment technique has been developed which enables control of the surface roughness and morphology of diamond films for applications in optical and electrical components. A conventional hot filament chemical vapour deposition (CVD) system was used to deposit the diamond films onto silicon substrates via a three-step sequential process: (i) deposition under normal conditions; (ii) exposure to either a pure hydrogen plasma or 3% methane in an excess of hydrogen using DC-bias; and (iii) diamond deposition for a further 2 h under standard conditions. The frictional characteristics and roughness of the film surfaces were investigated by atomic force microscopy (AFM) and the morphology and the growth rates determined from scanning electron microscope images. Lateral force microscopy (LFM) has revealed significant differences in frictional behaviour between the high quality diamond films and those modified by a glow discharge treatment. Friction forces on the diamond films were very low, with coefficients ∼0.01 against silicon nitride probe tips in air. However, friction forces and coefficients were significantly greater on the DC-biased films indicating the presence of a mechanically weaker material such as an amorphous carbon layer. A combination of growth rate and frictional data indicated that the exposure to the H2 plasma etched the diamond surface whereas exposure to CH4/H2 plasma resulted in film growth. Re-Nucleation of diamond was possible (stage iii) after exposure to either plasma treatment. The resultant friction forces on these films were as low as on the standard diamond film. |
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