Studies of pulsed high-current arcs used to prepare carbon films

Abstract

Electric arcs have been widely used for the preparation of carbon films. In particular, the filtered cathode arc technique is known to be one of the best methods for the production of diamond-like carbon with high concentrations of sp 3-bonded carbon. In 1999 the possibility of producing diamond micro-crystallites [Nature 402 (1999) 162] using a high-current arc pulse, >1000 A with a 60-ms duration, between two 0.5-mm-diameter graphite rods. For such high-density plasma systems, the relative density of the deposit precursors, and their spatial variation, energy, degree of ionisation, etc. are very important, since these determine the characteristics of the deposits produced. In this paper we report optical studies involving time-resolved emission spectroscopy (identification of the emitted species at different delay times), time-resolved photography (temporal and spatial evolution of the arc) and shadowgraphy (temporal and spatial evolution of the plasma and particle formation) of a pulsed arc similar to that used in the microcrystalline diamond work. In addition, we report preliminary results of the characteristics of carbon films deposited on both a close substrate (as in the report in Nature) and on a variably biased substrate placed approximately 10 cm from the arc.