Growth of ultrananocrystalline diamond films in an Ar-rich CH4/H2/Ar atmosphere with varying H2 concentrations

Ultrananocrystalline diamond (UNCD) films were prepared by microwave plasma chemical vapor deposition using argon-rich CH 4 /H 2 /Ar plasmas with different H 2 concentrations from 5% to 20%. The influence of the H 2 concentration on the microstructure, morphology and phase composition of the UNCD films was investigated by SEM, XRD, surface profilometry and Raman spectroscopy. It is found that the grain size and surface roughness increase with the H 2 concentration. The grain size of the UNCD is less than 6 nm when the H 2 concentration is less than 10% and it is still less than 10 nm even when the concentration is 20%. The thickness of the UNCD films is 1.75, 1.80, 1.65 and 2.9 μm using H 2 concentrations of 5%, 10%, 15% and 20%, respectively. All the films are dense and compact in the cross section, and smooth on the top surface. [New Carbon Materials 2013, 28(2): 134–139]