An auger electron spectroscopy study of low temperature segregation of silicon at aluminum surface

Abstract

Low temperature surface segregation of silicon out of refined aluminum samples is studied by AES. The analysis of kinetics data gives an Arrhenius type diffusivity with an activation energy equal to 65 kJ mol −1 (0.68 eV atom −1). The pre-exponential factor is of the order of 3 × 10 −6 m 2 s −1. These results fit well within the limits of grain boundaries and dislocation diffusivities, as compiled from the literature by Hwang and Balluffi, and show that the segregation proceeds from distorted sites in grain boundaries and dislocations, rather than from bulk undistorted sites. The analysis of data obtained from a slow-cooling-rate experiment gives a segregation energy of −60 kJ mol −1 (−0.63 eV atom −1) and shows that the silicon surface concentration limit is not a monolayer, but rather unexpectedly about 8%. This may be related to LEED observation of silicon adsorption on various faces of aluminum by Jona and suggests that long range repulsive forces are effective to saturate silicon condensation on aluminum at a low coverage value.