Étude par spectrométrie de masse en vision directe des interactions sous basse pression du pentachlorure de tantale avec le tantale à haute température

Abstract

We have studied the kinetics of the pyrolysis of tantalum pentachloride at low pressure and high temperature using a tantalum ribbon placed in an ultra high vacuum apparatus; all of the reaction products were detected by means of line-of-sight mass spectrometry. For low chlorine surface coverages the reaction product is atomic chlorine, along with the formation of a tantalum deposit on the surface. At higher surface coverages tantalum tetrachloride is observed corresponding to an attack of the substrate. Together, these results were interpreted in terms of a theoretical model developed previously for the interactions between transition metals and oxygen containing molecules, then chlorine, and experimentally verified in all these cases. This model can be summarized by the existence of three steps: (i) the dissociative adsorption of the incident molecule, (ii) the desorption of atomic chlorine, and (iii) the desorption of the tetrachloride formed by surface reaction favored at high surface coverages.