Chemical effects in Auger electron spectra of aluminium

Abstract

The bonding and electronic structure of surface atoms is most often studied by XPS, where the energy shift of a photoelectron peak can be ascribed to a change in the chemical environment. Because three atomic levels are involved in the Auger emission process, the use of Auger spectroscopy to obtain this information from peak positions and lineshape is more difficult. However, new progress in signal analysis techniques makes the extraction of chemical information intrinsically present in the Auger spectra possible. The advantage of AES over XPS is its higher lateral resolution, allowing study of the surface distribution of the elements (Auger mapping). This, combined with modern computational methods, opens up new opportunities in surface analysis. In order to try to correlate the changes in the Auger peak energies with the changes in the chemical environment, we performed a full experimental and theoretical study of the Auger KLL lines of aluminium in several compounds (Al 2 O 3 , AlN, AlB 2 and AlF 3 ) by AES and x-ray-induced AES, the peak position for AlB 2 being reported for the first time. The inner-shell KLL peaks of Al show large energy shifts, depending on the chemical environment. The experimental results are compared to ab initio calculations based on a new cluster model including chemical, structural and relaxation effects.