Low energy electron collisions with some gaseous hydrides and deuterides

Abstract

The ratio of lateral diffusion coefficient to electron mobility (Dr/μ) has been measured in several gaseous Hydrides and Deuterides (CH4, CD4, SiH4, SiD4, PH3, H2S) using electron swarm techniques. These measured values have been combined with values of the drift velocity under the same conditions, where this is known (all but H2S), and analysed using a two term Boltzmann Analysis to produce electron - molecule cross sections.

The weaknesses of such an analysis are recognised, so a Monte Carlo simulation of the experiment was developed and tested as an independent means of checking the cross sections so produced. The cross section for methane (at energies less than 5 eV) was fully explored using the simulation, giving a quantitative assessment of the value for the Ramsauer — Townsend minimum in this gas, and establishing the form of the inelastic contributions around the region of the minimum. In the other gases for which two term cross sections were calculated (except phosphine which would stretch the present model beyond its limitations) the Monte Carlo approach has been used qualitatively to indicate the weaknesses of the two term approximation.