The field emission fluctuation method was used to measure the diffusion (figure 40) of H and D on the (110) plane. At temperatures below 140K, the diffusion of H corresponded to pure tunnelling. Here, the barrier height was 0.2leV and its width was 0.05nm. This was suggested to be associated with the saddle position that was formed by pairs of nearest-neighbor W atoms.

R.DiFoggio, R.Gomer: Physical Review Letters, 1980, 44[19], 1258-60

Figure 40

Diffusivity of D and H on the (110) Plane of W

(circles: H, squares: D)