Diamond-Like Coatings : Microstructural Evolution under Ion Beam Assistance

Abstract

Non-hydrogenated diamond-like carbon films have been prepared by Dual Ion Beam Sputtering and Ion Beam Assisted Magnetron. The assistance parameters -ion energy, ion mass, ion flux/atom flux- have been systematically varied and their effect on the microstructure of the films studied. The films have been characterised by Rutherford Backscattering Spectroscopy (RBS), High Resolution Transmission Electron Microscopy (HRTEM), Electron Energy Loss Spectroscopy (EELS), Positron Annihilation Spectroscopy (PAS), and Raman Spectroscopy (RS). RBS and PAS results showed that the density and the degree of disorder of the films go through a maximum with ion energy, and that the void concentration goes through a minimum. EELS and RS show that the films are mostly sp(2) bonded, with a maximum concentration of sp(3) bonding of about 16% for the largest values of density. The evolution of density with ion flux and energy is consistent with a combined effect of atomic displacements in the film leading to densification, and with damage buildup leading to progressive graphitisation as the energy is increased.