EFFECT OF ANNEALING AND HYDROGEN PLASMA TREATMENT ON THE VOLTAMMETRICAND IMPEDANCE BEHAVIOR OF THE DIAMOND ELECTRODE

Undoped polycrystalline diamond thin films have been grown on molybden um substrates by microwave-assisted chemical vapor deposition using a hydrogen and methane gas mixture. Cyclic voltammetric behavior of diam ond films has been studied in 0.5 M NaCl solution as a function of ann ealing in nitrogen gas at 425 degrees C and hydrogen microwave plasma treatments at 800 degrees C. Preliminary voltammetry studies have show n that the annealed diamond film has a high resistivity, and hydrogen microwave plasma-treated diamond has a low resistivity. These treatmen ts have an effect on the extent of the gas evolution reaction either i n the anodic or in the cathodic polarization of the diamond electrode. AC impedance and DC linear polarization techniques have provided the data on the increase and decrease in diamond film resistance upon anne aling and hydrogen microwave plasma treatment, respectively, which fur ther corroborates the voltammetry studies. These electrochemical measu rements may qualitatively suggest that there may be a change in electr on affinity characteristics of the diamond surface as a function of va rious pretreatments, (C) 1998 Elsevier Science S.A.