H2S INTERACTION WITH CU(100)-(2-ROOT-2X-ROOT-2)R 45-DEGREES-O - FORMATION OF A METASTABLE VERTICAL-BAR-52 05-VERTICAL-BAR-SULFUR SURFACE RECONSTRUCTION/

This paper utilizes scanning tunneling microscopy, low-energy electron diffraction, Auger-electron spectroscopy, and temperature-programmed desorption to examine a metastable \(52)(05)\-S structure which forms after the interface reaction of H2S with a Cu(100)-(2 root (2) over ba r X root (2) over bar)R45 degrees-O surface. This preoxidized copper s urface displays an entranced reactivity towards H2S compared to the cl ean and annealed Cu(100) surface. Exposing 15 L of H2S onto a Cu(100)- (2 root (2) over bar X root (2) over bar)R45 degrees-O surface causes all the adsorbed oxygen to desorb as H2O at 164 K, while leaving appro ximately 0.5 ML of adsorbed sulfur on the surface. When this sulfur ov erlayer is annealed between 525 and 600 K, a metastable \(52)(05)\-S r econstruction forms that is not observed after annealing similar cover ages of sulfur adsorbed on an initially clean Cu(100) surface. Heating the \(52)(05)\-S surface to temperatures above 600 K converts this st ructure to the thermally stable Cu(100)root<(17)over bar>X root<(17)ov er bar>)R14 degrees-S (i.e., \((1) over bar 4)(41)\-S overlayer. A mod el for the metastable \(52)(05)\-S reconstruction is proposed.