Modelling of bond structure and potential barrier of O-Cu(001) surface characterised by STM/S and VLEED

Chang Qing Sun

The O-Cu(00I) surface has been studied extensively for several decades. The existing static-structure models have contributed greatly to the advance of this regime but disputes still remain concerning the nature and formation of the OCu bond. Scanning Tunnelling Microscopy/Spectroscopy (STM/S) has provided dynamic visions of the reconstruction but quantitative information and a detailed description of the reaction dynamics is still lacking. The analysis of a variety of STM/S O-metal outcomes and VLEED spectra of the O-Cu(00l) surface leads to a new model of the bond structure and suggests that a non-uniform surface potential barrier (SPB) for O-metal surfaces is required. It is taken into account that the O possesses two bonding and two nonbonding orbitals and that the atomic radii vary with the alternation of their atomic states and their coordination surroundings. It is proposed that the Ometal reaction is a result of the hybridisation of the O generating two Goldschmidt-contraction ionic bonds and two nonbonding lone pairs and that the lone-pair-induced metal dipoles reinforce the SPB and reduce the local work function ØL(x, y). These models support Lang's Tunnelling theory regarding O-chemisorbed metal systems and explain the big protrusions on Ometal surfaces and the reduction of work function as arising from the metal dipoles. The formation of the lone-pair-zigzagged O-M chains and the presence/absence of missing rows is a consequence of the surface-bond formation. The generality of the bond model is shown by proposing four kinds of O-metal chains to explain the STM images of orderly reconstructed O-metal surfaces. The ability of the model to provide a quantitative description of the reaction dynamics is demonstrated by simulating the O-increasing VLEED spectra of the Cu(00l) surface with individual variation of only three bond-structure variables. It is found that the VLEED is as useful as STM/S in revealing information of the spatial electron distribution and the variation of the density of states in the shared energy window. This work therefore demonstrates the combination of STM/S and VLEED techniques as powerful complementary tools for revealing the processes of surface reconstruction.

Modelling of bond structure and potential barrier of O-Cu(001) surface characterised by STM/S and VLEED

Files and links (1)

Abstract

Details

Metrics