CYCLIC VOLTAMMETRIC, AC-POLARIZATION AND DC-POLARIZATION BEHAVIOR OF BORON-DOPED CVD-DIAMOND

Boron-doped polycrystalline diamond films have been deposited over a m olybdenum substrate by the microwave plasma CVD process using a methan e and hydrogen gas mixture at a pressure of 35.7 Torr. Boron doping of diamond has been achieved in situ by using a solid boron source while growing diamond in the CVD process. The a.c. impedance of boron-doped diamond films in 0.5 M NaCl solution has been determined and compared with the results obtained with a molybdenum substrate. Capacitance, s olution resistance, and polarization resistance (corrosion rate) have been determined using the experimental data plotted in Nyquist and Bod e formats. D.C. polarization techniques such as linear and Tafel polar ization have been used to evaluate the doped diamond coated molybdenum and molybdenum for corrosion resistance characteristics in terms of c harge-transfer coefficients and corrosion rate. Cyclic voltammetry has been used to evaluate the molybdenum, platinum, and doped and undoped diamond coated molybdenum materials in 0.5 M NaCl solution, We have o bserved two time constants with a doped diamond electrode/solution int erface. Solution resistance was found to be constant irrespective of t he electrode in the same electrolyte solution. (C) 1997 Elsevier Scien ce S.A.