AES study of surface segregation of Ge in amorphous Si 1− xGe x thin film alloys

Abstract

Surface segregation of Ge in amorphous Si 1− x Ge x thin film alloys was studied by Auger electron spectroscopy technique. The alloys (with Ge bulk concentrations in the range of 18–58 at.%) were prepared by DC magnetron sputtering and annealed in a UHV chamber in the temperature range of 653–673 K. The surface equilibrium data were evaluated using segregation kinetics and the bulk diffusion coefficient of Ge was estimated in the framework of the model developed by Lea and Seah. We show that the experimental data can be interpreted using the McLean–Langmuir isotherm. The estimated segregation energy is lower than the theoretical one calculated in crystalline SiGe alloys neglecting the allowing and the size effects. We also found that the Ge bulk diffusion coefficient shows similar concentration dependence, as observed in amorphous SiGe multilayers.