Deposition and characterization of nanocrystalline diamond films prepared by ion bombardment-assisted method

Abstract

This article reports a process for preparing nanocrystalline diamond films by ion bombardment of different energies induced by applying a negative substrate bias voltage in microwave plasma-assisted chemical-vapor-deposition. The dependencies of the film morphology, grain size, growth rate, and average surface roughness on the substrate bias voltage were studied. The influences of substrate temperature, total gas pressure, and CH4 concentration on the grain size and growth rate were investigated. The results indicate that a high bias voltage, substrate temperature, CH4 concentration, and low total gas pressure are required to obtain high frequency of secondary nucleation so that smooth nanocrystalline diamond films can be prepared. High bias voltage, substrate temperature, total gas pressure, and CH4 concentration lead to high growth rate. Diamond films with a grain size and average surface roughness of several nanometers can be synthesized at a bias potential of −140 V. The micro-Raman spectroscopy shows a broad peak at around 1140 cm−1 which can be used to characterize nanocrystalline diamond films. The broad peak intensity from 1400 to 1600 cm−1 increases with decreasing grain size.