Ion induced alteration at Pb-Sn alloy surface investigated by Auger electron spectroscopy and X-ray photoelectron spectroscopy

The surface composition of a Pb-Sn alloy film on a Cu substrate was measured. The AES spectral intensities obtained under simultaneous Ar sputtering during analysis showed that the surface lead concentration decreased drastically, whereas the composition returned to its pre-sputtering value once Ar bombardment was discontinued. XPS analysis revealed that the intensity change is not due to any change of chemical state, but to preferential sputtering and diffusion of the lead atoms. Other possible factors, such as Auger electron emission induced by Ar ion bombardment, heating by the primary electron beam, and change of surface morphology caused by Ar sputtering, were also examined but found to be not significant.