SO2 FORMATION AT THE SULFUR-IRON OXIDE INTERFACE

We report SO2 thermal desorption (amu 64) from a polycrystalline iron surface precovered with a monolayer of S and subsequently overgrown with a thin Fe oxide layer under controlled UHV conditions. The assignment of SO2 to the amu 64 peak is confirmed by cracking pattern analysis. Studies using a combination of Auger electron spectroscopy (AES) and temperature-programmed desorption (TPD) show that SO2 exhibits a maximum desorption at 500 K. Our results demonstrate S-O bond formation at the metal-oxide interface and suggest a mechanism for the S-induced oxide instability.