Studies of Cu/Ru(0001) and Cu/O/Ru(0001) Surfaces by LEIS, AES and LEED

Abstract

Studies of Cu/Ru(OOOI) and Cu/O/Ru(OOOl) surfaces were made by applying low energy Li+ and He+ ion scattering with a combination of Auger electron spectroscopy, low energy electron diffraction and computer simulation. It was found that Cu grew on Ru(0001) layer-by-Iayer for the first two layers. Using Li+ ions, the results obtained by analysing the incident angle dependence associated with shadowing of Ru by Cu confirmed that the first layer Cu was in a normal registry position, i.e, there was a continuation of the hexagonal close-packed stacking sequence. The second layer Cu was determined to be in registry along the long azimuth (one of three possible domains) by analysing the shadowing features for the second layer Cu focusing onto the first layer Cu atoms. The Cu/O/Ru(0001) surface was also studied by He+ ion scattering. During deposition of Cu, the great majority of oxygen (about 70%) originally on the clean Ru(OOOl) surface was found to float out onto the top of the growing Cu overlayers. This displacement process could be observed up to Cu coverages of 10 ML, which appeared to be independent of the deposition rate, the 0 precoverage and the substrate temperature. The floating 0 atoms in the top layer have been determined to be a disordered overlayer by measuring the azimuthal scan dependence at grazing incidence.