Characterization of the annealed CoTi (110) surface and its interaction with molecular oxygen at room temperature

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Abstract
The annealed surface of CoTi single crystal oriented (110) has been characterized by AES, low‐energy electron diffraction (LEED) and electron energy‐loss spectroscopy (ELS), and the nature of its interaction with molecular oxygen at room tempertature has been studied. In the cleanest achieveable condition (5a/o oxygen irreducible minimum), the AES and LEED observations were consistent with a model in which the outer two atom layers consisted of titanium in registry with the underlying CoTi (110). Support for the model came from ELS, in which the titanium plasmon losses were shifted upwards in energy due to the smaller unit cell volume in the titanium film, and an interface plasmon loss was also found.Reaction with oxygen up to a maximum exposure of 3000 L occurred exclusively with the titanium component, the rate of reaction being about an order of magnitude slower than that observed by other workers on pure bulk titanium. The O/Ti atomic ratios measured at all stages of oxidation by AES, and the associated fine structure at each stage in the Ti LMM Auger spectra, were consistent with a process of oxidation first to TiO and then to Ti2O3, without the higher oxides appearing simultaneously. The maximum exposure used was insufficient for complete oxidation to TiO2. The ELS observations during oxygen exposure were in agreement with the proposed process.