Scanning tunnelling microscopy was used to investigate the formation of the 2 x n vacancy line structure on (001) surfaces. It was found that quenching the surface from high temperatures resulted in the formation of vacancies. After further quenching, these vacancies formed chains which ran perpendicularly to the dimer rows. Finally, the vacancy chains linked and developed into vacancy lines which extended for many hundreds of nm. Each vacancy line consisted mainly of 2 types of dimer vacancy. One of these was a di-vacancy, and the other was a combination of a single vacancy and a di-vacancy which were separated by an isolated dimer. All of the vacancy lines, together with the dimer rows, formed a 2 x n structure, where n was between 6 and 12. Calculations which were performed by using the Stillinger-Weber potential supported the view that the formation of the vacancy line structure was due to interactions between vacancies.

A.R.Smith, F.K.Men, K.J.Chao, Z.Zhang, C.K.Shih: Journal of Vacuum Science and Technology B, 1996, 14[2], 909-13