Papers by Author: Homero S. Maciel

Abstract: A DC dual magnetron sputtering system with graphite (C) and silicon (Si) targets was used to grow stoichiometric and non-stoichiometric silicon carbide (SixCy) thin films at low temperature. Two independently DC power sources were used to enable the total discharge power be shared, under certain proportions, between the Si and C magnetron cathodes. The motivation was to control the sputtering rate of each target so as to vary the stoichiometric ratio x/y of the deposited films. The species content, thickness and chemical bonds of as-deposited SixCy films were studied by Rutherford backscattering spectroscopy (RBS), profilometry analysis and Fourier transform infrared absorption (FTIR), respectively. Overall, the present work reveals a new reliable plasma sputtering technique for low temperature growth of amorphous SixCy thin films with the capability of tuning the degree of formation of a-SiC, a-Si and a-C bonds in the film bulk.

Abstract: A formula for quick calculation of thermal characteristics of materials used for thermal protection is proposed. The mode of heating of the sample external surface (subjected to thermal exposure) is approximated by two regions, which differ by corresponding boundary conditions on the heating surface: T_f=cτ (linear growing with time) and T_f=const (with permanent temperature of destruction). That approximation permits to obtain an analytical solution in integral form. In order to simplify and accelerate data treatment, a simple empirical formula is proposed. A contribution of each thermal region is proportional to the regime duration. A good agreement with an analytical solution is shown.