A new probe of bonding states in intermetallic compounds

This paper reports an investigation of a set of Ti-Al-based alloys by X-ray photoelectron spectroscopy. A new method for interpretation of the X-ray photoelectron spectrum allows a peak-shape parameter kappa to be defined, which links the intrinsic energy loss,structure associated with a given line in the spectrum to atomic number. This parameter enables quantitative interpretation of steps in background intensity which are related to the number of final state configurations available to the photoexcited atom or ion. We have investigated the extent to which aluminium orbitals interact with the 3d transition metal structure of titanium by comparing the values of kappa for the pure metals with those for the titanium and aluminium peaks in the intermetallic compound. We conclude that this gives direct evidence for bond overlap in these alloys. The results on kappa were then compared with the Auger parameters which are also related to the relaxation process following the photoemission and therefore indicative of the charge transfer mechanism occurring between Al and Ti. In undertaking this study, which required the preparation of the intermetallic compounds for spectroscopic analysis, we have had to investigate various means of sample preparation. In particular we have developed a means by which the bulk metal structure can be exposed and transferred with minimal oxidation using an in situ milling device.