Impedance study on electrochemical characteristics of sputtered DLC films

Diamond-like carbon (DLC) films with different structure were deposited on highly electrically conductive silicon substrates (SiO2/Si), using d.c. magnetron sputtering deposition process. Their structure and electrochemical behavior in a 0.5 M H2SO4 solution were studied with micro-Raman spectroscopy, electrochemical impedance spectroscopic analysis and film impedance spectroscopy The combined polarization resistance of silicon coated with DLC film increased to approximately 10(6)-10(8) Omega cm(2), while the combined capacitance decreased to 10(-7)-10(-8) F cm(-2). The double layer capacitance on the DLC films was approximately 0.571-3.91 X 10(-6) F cm(-2), which was smaller than that of popular electrode materials (graphite, platinum and mercury) and comparable with that of diamond. The double layer capacitance increased with the increased Raman spectrum intensity ratio I-D/I-G and accelerated at approximately I-D/I-G = 2.25. These results suggest that the DLC films be good insulating and corrosion protection coatings in sulfuric acid and potential electrode materials for electrochemical analysis. (C) 2002 Elsevier Science B.V. All rights reserved.