Auger parameter of hafnium in elemental hafnium and in hafnium oxide

Abstract

X-ray photoelectron spectroscopy has been used to determine the Auger parameters in elemental hafnium and in hafnium oxide (HfO 2). The zirconium L α line has been used as a source of excitation to study the 3d core levels of hafnium, the 1s core level of oxygen, and the X-ray excited MNN Auger region of hafnium and KVV Auger region of oxygen. The Auger parameters for hafnium and oxygen have been determined from these spectral data. In case of oxygen, the Auger parameter has been compared with the corresponding value in water. The change in the Auger parameter is observed to be negative for hafnium and positive for oxygen. We have shown that the opposite signs of the Auger parameters in binary systems can be utilized to determine the direction of charge transfer between the constituents. This is consistent with the chemical shift due to charge transfer. This chemical shift in the core level has been evaluated by subtracting the relaxation shift from the experimentally observed core level shift. It is found to be positive for the 3d 5/2 core level of hafnium in the oxide indicating a charge transfer from hafnium to oxygen in the oxide. The observations are consistent with Pauling’s electronegativity criterion.