X-ray absorption spectroscopy of Ag-Cr and Pd-Cr alloys formed by ion-beam-mixing

In this paper, we discuss X-ray absorption spectroscopy and Auger electron spectroscopy results that elucidate the local atomic arrangements and electronic structure change of ion-beam-mixed Ag-Cr and Pd-Cr alloys. Cr K-edgespectra were used to investigate the local crystal structure in these ion-beam-mixed thin film alloys. In ion-beam-mixed Ag-Cr thin films with a large positive value of heat of formation (ΔHm) the local crystal structure of the Cr site does not change, but in ion-beam-mixed Pd-Cr thin films with large negative value of ΔHm the structure of Cr site changes from a bcc to an fcc structure with increasing Pd concentration. In addition, Pd L3 X-ray absorption near-edge measurements show a decrease of the white line feature associated with the transition from 2p core level to 4d empty band in the Pd site of ion-beam-mixed Pd-Cr alloys. In contrast to the Pd-Cr system, the Ag L3 near-edge spectra remain unchanged in the ion-beam-mixed Ag-Cr system. It is thus concluded that the ion-beam-mixed Ag-Cr thin films consist of a mixture of elemental domains with no obvious indication of intermetallic alloying or compound formation as a consequence of the positive heat of mixing.