Mobility of atoms on the (320) and (221) regions of a W microcrystal surface with a tip curvature radius of about 300nm, and the surface diffusion of Dy at an average coverage of about 0.1ML, were investigated via the spectral analysis of field emission current fluctuations at 500 to 800K. The diffusion appeared to be one-dimensional for W(320) and two-dimensional for W(221). The surface-diffusion coefficients were determined by comparison of the experimental

results with theoretical spectral density functions. The results could be described by:

(320):     D (cm2/s) = 4.0 x 10-9 exp[-0.31(eV)/kT]

(221):     D (cm2/s) = 2.7 x 10-6 exp[-0.49(eV)/kT]

T.Biernat, R.Błaszczyszyn: Applied Surface Science, 2009, 255[13-14], 6593-7