Plasma polymerization anda-C:H film ablation in microwave discharges in methane diluted with argon and hydrogen

Abstract

Neutral hydrocarbons are observed from a microwave discharge in a fast flow of (A) 0.5–6% methane in argon, (B) 0.5–6% methane in hydrogen, and (C) hydrogen over a previously depositeda-C:H film. System (A) produces polyacetylenic and other hydrocarbons through C8 by predominantly gas-phase reactions and deposits ana-C: H film. Reactions under conditions (B) and (C) produce hydrocarbon radicals and molecules with masses through 300 that in case (B) arise from both gas-phase reactions and film ablation, and in case (C) from film ablation alone. Proposals are made for the mechanisms of gas-phase polymerization, film deposition, and ablation. Hydrocarbon ions observed downstream from these discharges appear to arise from ionization of neutral species with a distribution determined by subsequent ion-molecule reactions and selective diffusion losses.