THE MEANDERING OF STEPS AND THE TERRACE WIDTH DISTRIBUTION ON CLEAN SI(111) - AN INSITU EXPERIMENT USING REFLECTION ELECTRON-MICROSCOPY

In situ reflection electron microscopy experiments have been done on steps in thermodynamic equilibrium on clean Si(111) surfaces (900-degrees-C). Isolated steps and step trains (mean step separation from 20 to 140 nm) have been studied. From the thermal fluctuations of isolated steps we deduce a value of (roughly) 1 x 10(-10) J m-1 for the line tension of a step at 900-degrees-C. The terrace width distribution has a standard deviation which varies linearly with the mean separation between steps up to mean step distances of 70 nm at least. Over the whole range of step mean separation the distributions are best fitted by a Gaussian law. This is attributed to step interactions decaying as Ax-2 (x normal distance to the step edge). The value of A is determined (A = 4.6 x 10(-30) J m at 900-degrees-C). The nature of these interactions is briefly discussed.