GROWTH AND REACTIVITY OF ZNOX ON CU(111)

The oxidation of the Zn/Cu(111) interface has been investigated by the methods of thermally programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS). The process has been studied for zinc coverages, theta(Zn), in the 0 < theta(Zn) < 3 monolayer (ML) range and for oxygen exposures up to 6000 L O2. It was found that a zinc oxide film formed at 103 K changes its composition to islands of ZnO(x), with x < 1, by annealing to 410-523 K with loss of oxygen. The new phase is characterized by three Zn states in the TPD spectra. The sequence of states, ranging from a zinc state at 820 K to Zn++ in ZnO at 978 K, ran be correlated with different O(1s) binding energies. One of the three zinc components, positioned at the boundary of the ZnO(x) islands, reacts with oxygen and is transformed to a state with a higher oxidation step. A model for the zinc oxide formation at the Zn/Cu(111) interface is proposed.