The diffusion of Sb was measured by means of optical second-harmonic microscopy. Concentration profiles of sub-monolayer coverage were imaged with a spatial resolution of 5μ. A Boltzmann-Matano analysis then revealed the coverage dependence of the diffusivity, without parametrization, at an homologous temperature of 0.7. At coverages of up to 0.6, the activation energy remained constant at 47.5kcal/mol while the pre-exponential factor decreased from 8.7 x 103 to 1.6 x 102 cm2/s (table 37). The values of the diffusion parameters were relatively high. A new vacancy model was proposed for diffusion at low coverage. This model accounted semi-quantitatively for the large values of the diffusion parameters. It was suggested that these parameters could be affected by adjusting the dopant level and the photon illumination. The decrease in the pre-exponential factor with coverage was attributed to islanding effects.

K.A.Schultz, E.G.Seebauer: Journal of Chemical Physics, 1992, 97[9], 6958-67

Figure 26

Diffusivity of Si in Ge