Oxidation of Al–Au intermetallics and its consequences studied by x-ray photoelectron spectroscopy

Three common Al–Au intermetallics, Al₂Au, AlAu₂, and AlAu₄, were oxidized in the air and characterized using x-ray photoelectron spectroscopy in terms of the elemental chemical state. It was found that there is an increasing trend of oxidation in these intermetallics as the Au content increases. AlAu₄ shows the greatest tendency to oxidize with two extra peaks appearing on the Au 4f spectra after long exposure time in air. The surface of AlAu_2, although fully oxidized, reveals only one Au 4f peak shift as depth increases. Al₂Au was the least oxidizing compound, and the oxide is thin. The binding energies of Al 2p and Au 4f peaks were measured and reported. The Au atoms trapped in the oxide layers exhibit higher binding energy emissions compared to those of elemental Au.