Chemical self-diffusion coefficients, D, as a function of temperature and metal vapour pressure, PZn, were studied in undoped single crystals at high temperatures. At 750 to 850C, D could be described by:

D (cm2/s) = 4.5 x 10-3 exp[-0.69(eV)/kT]

At 1050 to 1150C, D was given by:

D (cm2/s) = 1.2 x 10-4 exp[-0.43(eV)/kT]

The phase transition region was characterized by confused values of D because of changes due to phase mixture. The value of D was about 3 orders of magnitude faster than that for self-diffusion under the same conditions. It was shown that doubly-ionized interstitial metal atoms were the predominant diffusible defects at high metal vapour pressures. The value of D was found to be almost independent of the metal vapour pressure at high PZn.

Chemical Self-Diffusion in Undoped ZnS and in Undoped CdSe. K.Lott, T.Nirk, O.Volobujeva: Crystal Engineering, 2002, 5[3-4], 147-53

Figure 30

Diffusivity of Cu in ZnS