Deposition of Amorphous Carbon Films from Laser-Produced Plasmas

Abstract

AbstractAmorphous carbon films deposited by sputtering or ion-beam techniques, as well as a-C:H films produced by glow discharge in hydrocarbon vapor, can exhibit interesting and desirable properties such as hardness, wide optical gap, high resistivity and chemical inertness. A critical parameter common to all methods for producing such films appears to be kinetic energy of the ions or atoms incident on the growing film. We report an investigation of laser-produced carbon plasmas as a deposition source which can supply ions and atoms having energies requisite for the production of hard carbon films. The plasmas were generated by focusing 1.06 μm radiation from a Q-switched Nd:YAG laser onto a carbon rod which could be rotated within the vacuum chamber to present a fresh surface for each shot. Plasma temperature, varied as a function of laser pulse energy, was monitored by recording X-UV plasma emission spectra during deposition. Films having thicknesses up to ˜0.5 μm were deposited on various substrates and were evaluated by microscopic inspection, thickness profiling, optical transmission measurements and hardness testing. Hardness increased significantly with plasma temperature, from about 3 to over 7 on the Mohs scale. There was no corresponding increase in optical gap, which remained near 0.4 eV for all films.