Epitaxial nucleation of diamond on an iridium substrate by bias treatment, for microwave plasma-assisted chemical vapor deposition

An Ir layer was epitaxially grown on a MgO(100) substrate by radio frequency magnetron sputtering, and was used as the substrate for the epitaxial growth of diamond by microwave plasma-assisted chemical vapor deposition (MPCVD) using CH4-H-2 systems. The Ir(100) layer was then bias-treated under a wide variety of conditions. Thus, a bias voltage of -150 V, a methane concentration of 3%, and a continuation of 15 min, were determined to be the optimum conditions. In the subsequent diamond growth step, oriented diamond particles, 100-250 nm in size with pyramidal structures, were formed at a population density of (0.15-1.5)x 10(8) cm(-2). It is noteworthy that the fraction of oriented particles was nearly unity. Tilted or rotated diamond particles were seldom observed. Substrate erosion and graphitic carbon formation, also often observed in the case of Ni and Pt substrates, were not found during the diamond deposition on the Ir(100) substrate. (C) 1998 Elsevier Science S.A.