Influence of the secondary electron emission on the characteristics of radio frequency plasmas

In this paper the influence of secondary emission on the characteristics of RF plasmas has been studied. An asymmetrical dual-frequency capacitively coupled plasma reactor has been modeled with one dimensional PIC/MCC (Particle in Cell with Implemented Monte Carlo Collisions) code. The main feature of the modeling code represents the realistic model of the ion-induced secondary electron emission. Secondary emission of electrons is one of the important processes that effects the characteristics of rf plasmas. For modeling the secondary yield per ion, we have used equations proposed by Phelps and Petrović (Plasma Sources Sci. Technol. 8 (1999) R21-R44) for differently treated metal surfaces. In the model, the energy dependence of the yields per ion for differently treated metal surfaces has been implemented. Results are compared for yields for the so called “dirty” and “clean” surfaces, and the spatial profiles of charged particles and ion energy distributions were observed. The simulation results indicate that the plasma characteristics are greatly affected by the ion-induced secondary emission, changing the overall parameters of dual-frequency capacitively coupled plasma reactors especially in applications as etching devices. Conclusion is that an exact model of the secondary electron emission should be included, as to ensure better agreement between simulation and experiment

Thermomagnetic Analysis of Nanocrystalline Nd4.5Fe77B18.5 Alloy

Changes in the phase composition and crystallite size of a rapid quenched Nd4.5Fe77B18.5 alloy, caused by thermomagnetic measurements (TM) have been studied using XRD methods of phase analysis. crystallite size and lattice microstrain determination. Structural changes in regard to optimal magnetic state were additionally analyzed by TEM. Magnetic properties in optimal magnetic state and after TM were observed using room temperature SQUID measurements. The obtained experimental results suggest the Fe3B/Nd2Fe14B and partly alpha-Fe nanocomposite structure of the alloy in the optimized magnetic state. with mean crystallite size (< 30nm). After TM. an increased amount of alpha-Fe phase, presence of different oxide and Fe-B phases as well as growth of crystallites are found to be the main reasons for the observed quality loss of hard magnetic properties.close4