Flow-field properties under deposition of films from low-density jets

Abstract

Statistical methods in the direct simulation Monte Carlo procedure and the electron-beam fluorescence technique were applied to investigate the distribution of density and temperature in a monatomic jet. Initial conditions of investigated flows corresponded to ones under deposition of films from low-density jets. In calculations, the variable hard-sphere model for molecular interaction potential and the diffuse reflection model with complete thermal accommodation were used. Distribution of density of Ar atoms in the jet and in the vicinity of the substrate were measured by the spontaneous radiation of Ar i 5912 Å (transition 4p[1/2]←4d[3/2]0,1←1′) and Ar ii 4610 Å (4s′2D←4p′2F0,5/2←7/2) induced by the electrons. The temperature was evaluated with the rotational temperature of N2, a small portion (5%) of which was added into Ar. The quantities of rotational temperature were found by measuring the intensity of the rotational lines of the first negative system N+2 band. The experimental data provide information about profiles of density along and across the center line of a jet over a range of 1×10−3≤Kn*≤4×10−2. On the whole, the computed profiles of density are in good agreement with the measurements. The calculated properties in the vicinity of the substrate allowed the performance of a detailed analysis of the gas-surface interaction process. A good comparison of the computed profile of the flux of molecules, incident on the substrate, and data on the film thickness of a-Si:H were obtained.