Detection of CuAuPd Phase Boundaries Using Core Level Shifts

A high throughput study has been conducted of the Cu 2p_3/2, Au 4f_7/2, and Pd 3d_3/2 X-ray photoemission spectra obtained from a continuous distribution of Cu_xAu_yPd_1-x-y alloy samples prepared as a single composition spread alloy film (CSAF). All three elements exhibit shifts of their core level binding energies with respect to their pure states when diluted into the alloy. The Cu 2p_3/2 core level shift (CLS) exhibits additional shifts over the composition ranges at which the Cu_xAu_yPd_1-x-y alloy transitions between FCC and B2 phases. This discontinuous CLS has been used to map the extent of the B2 phase across the ternary Cu_xAu_yPd_1-x-y alloy composition space. The sensitivity of core level binding energies to the alloy phase offers an opportunity to use XPS to study phases in alloy nanoparticles, ultrathin films, and other morphologies that are not amenable to structure determination by diffraction based methods.