Synthesis of ultrananocrystalline diamond films by microwave plasma-assisted chemical vapor deposition

In this paper, we report on the development of process methods and apparatus that enable the deposition of ultrananocrystalline diamond (UNCD) films over a wide pressure range (60-240 Torr) and temperature range (400-800 degrees C). The films are deposited using a microwave plasma-assisted chemical vapor deposition (MPCVD) system operating at 2.45 GHz with variable power and pressure. The influence of various input parameters such as feed gas mixture, pressure, and substrate temperature on the growth rate and surface morphology/roughness of the UNCD diamond films is investigated. Feed gas mixtures studied include argon-methane-hydrogen, helium-methane-hydrogen and argon-methane-nitrogen. Experimental data are reported for the growth rate, crystal size distribution, surface roughness, Young's modulus, and electrical conductivity.