“In situ” XPS studies of laser-induced surface nitridation and oxidation of tantalum

This work studies the nitridation of Ta by laser irradiation by means of x-ray photoelectron spectroscopy. The study has been carried out under “in situ” conditions by controlling the nitrogen partial pressure, the presence of traces of oxygen, and the irradiance of the laser. It is found that a thin layer of Ta2O5is directly obtained when irradiating in the presence of oxygen, while a Ta3N5surface compound and some minor contributions of nonstoichiometric phases are formed in the presence of nitrogen. For O2:N2mixtures at 0.1 Pa, preferential nitride formation occurs up to a ratio of 1:4, while Ta2O5starts to be predominant for ratios above this value. The air stability of the tantalum nitride layer formed by laser irradiation and the surface topography of the irradiated metal are also studied. The possible factors determining this behavior are discussed.