The migration of Li on the (112) plane was investigated by using the field emission fluctuation method. A rectangular slit was used as a probe hole which could be rotated in situ. The spectral density functions of the field emission current fluctuations for 2 perpendicular slit positions (along [111] and [110]) were measured. The activation energies for various Li coverages were deduced from the temperature dependence of the diffusion coefficient at temperatures ranging from 390 to 530K (table 268). An anisotropy was found for a wide range of Li coverages. The surface diffusion activation energy was higher for the [110] direction than for the [111] direction. Values of 0.54 and 0.46eV, respectively, were obtained for a relative Li concentration of 0.6 (table 269). The anisotropy was attributed to the substrate atomic structure.
T.Biernat, C.Kleint, R.Męclewski: Applied Surface Science, 1993, 67, 206-10
Table 268
Diffusivity of Li on the (112) Surface of W
Li Relative Concentration | Direction | Temperature (C) | D (cm2/s) |
0.6 | [111] | 257 | 4.5 x 10-8 |
0.6 | [111] | 211 | 2.2 x 10-8 |
0.6 | [111] | 174 | 4.8 x 10-9 |
0.6 | [111] | 137 | 2.4 x 10-9 |
0.6 | [110] | 257 | 4.7 x 10-8 |
0.6 | [110] | 211 | 1.4 x 10-8 |
0.6 | [110] | 174 | 3.3 x 10-9 |
0.6 | [110] | 137 | 1.1 x 10-9 |
0.9 | [111] | 231 | 3.8 x 10-8 |
0.9 | [111] | 192 | 1.8 x 10-8 |
0.9 | [111] | 161 | 5.8 x 10-9 |
0.9 | [111] | 137 | 2.1 x 10-9 |
0.9 | [111] | 127 | 1.4 x 10-9 |
0.9 | [110] | 231 | 2.9 x 10-7 |
0.9 | [110] | 192 | 1.7 x 10-8 |
0.9 | [110] | 161 | 4.0 x 10-9 |
0.9 | [110] | 137 | 3.9 x 10-10 |
0.9 | [110] | 117 | 1.8 x 10-10 |