STM and DFT study of the Gd wetting layer reconstructions on the Si(001)-2 x 1 surface

This paper presents a structural study of the 2 x 8 and 2 x 7 wetting layer reconstructions that occur on the Si(100) surface following Gadolinium deposition at elevated temperatures. Scanning tunneling microscopy and density functional theory calculations were used to analyze the detailed structure of the wetting layer. The maxima observed in STM images are consistent with the location of metal atoms determined by geometry optimized DFT calculations. In the 2 x 8 reconstruction metal atoms occupy the dimer positions but with a modulation in height that serves to lower the stress along the dimer row direction. The 2 x 7 reconstruction is formed by the redistribution of metal atoms of the 2 x 8 reconstruction, where the metal can occupy either the dimer position or a bridging site between two silicon atoms. (c) 2005 Elsevier B.V. All rights reserved.