Initial stages of oxygen adsorption on In/Si(111)-4x1

초록

The In/Si(111)4x1 surface with In wires is a prototypical one-dimensional electron system showing a temperature-induced structural phase transition. While most impurities are known to decrease the transition temperature (T-c), oxygen was reported to increase the T-c. In order to understand the exceptional influence of oxygen, we have examined the initial stages of oxygen adsorption on the surface by scanning tunneling microscopy (STM) and density-functional theory (DFT) calculations. Oxygen molecules were found to dissociate and adsorb as atoms on the surface. STM revealed three distinct O adsorption features as well as occasional transformations from one to another. The high-resolution images showed that all three adsorbed O features were located at the center of the In trimer at both edges of the In wire. This registry is in contradiction with the previous theoretical predictions [S. Wippermann et al., Phys. Rev. Lett. 100, 106802 (2008)]. The present DFT calculations identified two of the features as O atoms incorporated in the interstitial region between the In wire and subsurface Si layer.

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