The behavior of the (001) surface was studied at temperatures ranging from 120K to room temperature by using a low-temperature scanning tunnelling microscope. Investigations were made of 2 quite different types of surface. One was the normal 2 x 1 surface, and the other was the 2 x n surface, where n was between 4 and 12. In the case of the 2 x 1 surface, the defects were randomly scattered. By plotting the fraction of buckled dimers as a function of temperature, it was found that there was a slow transition from a mainly c(2 x 4) form at low temperatures to a mainly 2 x 1 form at room temperature; for a defect concentration of about 8.5%. In the case of the 2 x n surface, the much larger number of surface vacancies led to the formation of long-range ordered chains which divided the surface into many short dimer segments. These dimer segments appeared to be largely unbuckled at room temperature. Upon cooling to 190K, very little change was observed in the degree of buckling.

A.R.Smith, F.K.Men, K.J.Chao, C.K.Shih: Journal of Vacuum Science and Technology B, 1996, 14[2], 914-7