Surface composition and structure of Ni–Cr sputtered coatings exposed in air at room temperature

Nichrome coatings have been deposited using the d.c. sputtering of the target (80% Ni–20% Cr wt.) by Ar+ ions at a working pressure of 10−1 Pa and at room temperature. After the air exposure of samples at room temperature, their phase composition and structure was studied by X-ray diffraction, while the surface elemental composition was determined by low energy ion scattering (LEIS) and Auger electron spectroscopy (AES). AES has been also used for the bulk composition analysis. There is a significant difference between the compositions of the surface and of the bulk. Surface segregation of chromium was observed using both LEIS and AES, and it was found that the chromium concentration increases with that of oxygen adsorbed at the surface during the air exposure. The nichrome surface composition is qualitatively the same as in the case of its exposure to O2 at room temperature, but significantly different from that of the thermally annealed nichrome to 400 °C in air.