It was pointed out that, although surface diffusion had been studied at the atomic level for decades, little was known about the jump processes in self-diffusion. The diffusion of W atoms on the densely packed W(110) plane was therefore examined here (figure 41) by using a field ion microscope to determine the contributions of jumps other than those between nearest-neighbor sites. Measurements of the mean-square displacements of atoms along the x and y axes (<001> and <110>, respectively) and of the detailed spatial distribution of atomic displacements served to define the nature of the jumps which were important in diffusion. It was shown that, in addition to nearest-neighbor and second-nearest-neighbor transitions along the close-packed <111>, atoms also performed jumps along <001> and <110>, and that the contributions from these processes increased rapidly with temperature.

S.M.Oh, K.Kyuno, S.J.Koh, G.Ehrlich: Physical Review B, 2002, 66[23], 233406 (4pp)

Figure 41

Self-Diffusivity on the (110) Plane of W

D (cm2/s) = 5.4 x 10-3 exp[-0.95(eV)/kT]