Behavior of zirconium onZrO/W(100)surface

A preliminary examination to understand a lowering mechanism of workfunction on theZrO/W(100)surface is reported. X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) were employed for this purpose. After deposition of about 3 monolayers of zirconium onto clean W(100) surface followed by heating in an oxygen ambient, the zirconium overlayer completely changed to ZrO2 layer. In depth profile of this surface, the ZrO2 was detected deep in the bulk, implying that the ZrO2 was diffused into the bulk by heating in the oxygen. The surface that was covered with the ZrO2 showed an unclearp(1 × 1)pattern. Following flash heating in an UHV gave rise to disappearance of the ZrO2 and formation of Zr-O complex layer, which was accompanied by lowering of workfunction. Ap(4 × 2)superstructure pattern was observed in the LEED observation on the surface. Depth profile on the surface showed that the zirconium exists at the utmost surface, taking the form of Zr-O. These results imply that theZrO/W(100)surface is formed by transformation from the ZrO2 to the Zr-O complex and the taking the particular arrangement of Zr-O on the W(100) surface.