Measurements of Cd self-diffusion were carried out in an atmosphere of excess Cd at temperatures ranging from 350 to 650C. The diffusion profiles were measured by using an anodic oxidation sectioning technique, and revealed 2 components. These were a shallow Fickian one, and a second and much deeper component which was non-Fickian. When the results for the shallow diffusion component were combined with previous data, an Arrhenius plot was obtained in which the diffusion coefficient extended over nearly 9 decades, for temperatures ranging from 350 to 920C. The graph could be described as being the sum of 2 exponential functions of the forms:

D (cm2/s) = 1.25 x 102 exp[-2.55(eV)/kT]

D (cm2/s) = 2.48 x 10-8 exp[-1.08(eV)/kT]

This indicated that at least 2 diffusion mechanisms were operating over this temperature range. No significant difference was observed in the diffusion coefficients for bulk and epitaxially grown material, and no significant pressure dependence was observed at 489C. In the case of the shallow diffusion component, the agreement with previously published data was good at temperatures above 625C whereas, at lower temperatures, agreement with the limited amount of published data was poor. This was suggested to be due to the higher purity of the material which was used in this study.

E.D.Jones, N.M.Stewart, J.B.Mullin: Journal of Crystal Growth, 1993, 130[1,2], 6-12

Figure 7

Self-Diffusion of 109Cd in Te-Saturated CdTe