Amorphisation and Growth Mechanisms of Carbon Films under Ion Beam Irradiation

Abstract

Amorphisation mechanisms during Physical Vapour Deposition of diamond-like carbon films are presented and illustrate the role of ion bombardment on the microstructure and disorder of the deposited films. It is shown that, at low energy, densification of the carbon film is produced by an ion pinning effect, leading to cross-bonding between graphitic planes present in the layers. Increase of the sp3 concentration is observed as ion energy is increased until an optimum value at which irradiation induced defect migration leads to graphitisation of the layers. The effect of amorphisation–recystallisation depends strongly on the ion mass, ion energy and ion flux per deposited atom. A simple model of the ion beam assisted deposition mechanism is proposed and is in good qualitative agreement with experimental results.