Behavior of zirconium surfaces in the presence of oxygen, nitrogen, and hydrogen containing adsorbates

Abstract

As part of an effort to address questions related to corrosion passivation in zirconium alloys, low energy electron diffraction (LEED) and temperature programmed desorption (TPD) techniques have been applied to the adsorption of water and ammonia on Zr(0001). Water adsorption at 180 K results in water desorption in a broad TPD feature near 625 K. Ammonia exposure at 150 and 180 K results in the unexpected production of water during TPD near 625 and 525 K, respectively, and the formation of complex residual LEED patterns. Auger electron spectroscopy indicates that nitrogen remains at or near the surface following ammonia adsorption and TPD. A phenomenological explanation involving a temperature-dependent dissociation probability for ammonia and nitrogen/oxygen exchange between the surface and subsurface regions is presented to qualitatively account for these findings.