An unusual defect structure which occurred on the (001) surface was studied by means of 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