Pulsed electrodeposition of diamond-like carbon films
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Pulsed electrodeposition of diamond-like carbon films Hao Wang,a) Ming-Rong Shen, Zhao-Yuan Ning, and Chao Ye Film Material Laboratory, Department of Physics, Suzhou University, Suzhou 215006, People’s Republic of China
He-Sun Zhu The Research Center of Materials Science, Beijing Institute of Technology, Beijing 100081, People’s Republic of China (Received 15 August 1996; accepted 16 July 1997)
Diamond-like carbon (DLC) films have been prepared by electrolysis of methanol solution using a pulse-modulated source. The deposition rate of the films is enhanced significantly compared to that of dc value. That the films do not contain bonded hydrogen is confirmed by infrared spectra. The structures of the films are characterized by Raman spectroscopy. These films show chemical inertness and hardness values in the range 12.5–19 GPa. Current-voltage characteristics of the films are measured, indicating that the resistivity is in the 107 V cm range and the breakdown field is larger than 1 MV cm21 .
Diamond-like carbon (DLC) films are generally and successfully prepared from the vapor phase in a variety of methods, which can be summarized into chemical vapor deposition (CVD) and physical vapor deposition (PVD).1 Attempts to prepare diamond and DLC films from the liquid phase by electrodeposition techniques were first made by Namba,2 and then by Suzuki et al.3 In our recent work, we have reported that DLC films could be prepared from the liquid phase by electrolysis of a methanol solution at a temperature below 65 ±C using a high potential dc source.4 Pulsed inductive gas discharge was applied to film deposition. Both the deposition rate and film quality were improved.5,6 Pulsed electrodeposition was also applied to prepare composition-modulated alloy films. These alloys exhibited unusual magnetic,7 electrical, and chemical properties,8,9 and also morphology evolution.10 Thus, pulse-modulation may have some significant effect on the film deposition process. Inspired by the above results, we made an attempt to prepare DLC films by electrolysis of methanol solution using a pulse-modulated source. The experimental setup has been described earlier.4 Analytically pure methanol was used as the electrolyte. The negative electrode is an n-type single-crystal silicon (100) substrate with a resistivity of 5–8 V cm and a size of 15 mm 3 20 mm 3 0.3 mm. The distance between the substrate and positive electrode (graphite) was set to 10 mm. A pulse-modulated source was used instead of a dc source. The modulation potential applied to the substrate could be changed from 0 to 21000 V. The modulation duty cycle could be changed from 0 to 50% a)
Present address: The Research Center of Materials Science, Beijing Institute of Technology, Beijing 100081, People’s Republic of China.
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J. Mater. Res., Vol. 12, No. 11, Nov 1997
and modulation frequency from 0 to 10 kHz. In this paper, all the films were deposited at 1000 V at 50% duty cycle and 10 kHz. The infrared absorption measurements were ca
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