Composition of a Clean and Sulphur Covered CuNi(100) Single Crystal Surface

Abstract

Surface composition of the CuNi(100) single crystal in the temperature range of 893=1073 K (620=800°C) has been investigated using low energy electron diffraction and Auger electron spectroscopy methods. A clean sample surface at moderate temperatures reveals small surface copper enrichment, with respect to the bulk Cu-rich composition. For example, at 1006 K (733°C) the copper surface concentration q„, was determined from the quantitative Auger electron spectroscopy analysis as 0.91. After prolonged heating at higher temperatures, the copper surface concentration converges to the bulk value, i.e. at 1073 K (800°C), CsCu = Cb u =0.87. Surface segregation of sulphur proceeds from (1 x 1) through p(2 x 2)S/CuNi(100) to c(2 x 2)S/CuNi(100) structures of low energy electron diffraction. In the presence of segregated sulphur the surface concentration of copper is lower.