LEED and XPS studies of the ZrOW(100) surface

The ZrOW(100) surface, which is used for thermal field emitters, was investigated by means of X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and workfunction measurement technique, simultaneously. Deposition of about 3 monolayers of zirconium on a W(100) single crystal surface followed by heating in an oxygen pressure of the order of 10−5 Pa gave rise to a peak shift of the Zr 3d peak to higher binding energy, which indicates formation of ZrO2 on the surface. This is accompanied by an increase of the workfuntion to 5.3 eV. Subsequent flash-heating at higher temperature in an ultrahigh vacuum created a “ZrO complex”, with an accompanying lowering of the workfunction. After heating at 2100 K, the ZrO2 completely disappeared and ZrO complex was present on the surface. This surface has a minimum workfunction of 2.7 eV. A LEED observation of this surface showed a characteristic c(4 × 2) pattern, which was clearly different from the p(1 × 1) pattern of the clean W(100) surface. These results imply that the formation of the ZrO complex and its particular arrangement play a very important role forming the low workfunction surface on the ZrOW(100