The diffusion of 50keV Na atoms which had been implanted into single crystals was studied after heating the crystals in flowing N or Ar at between 550 and 900C. It was found that deep penetration of interstitial Na occurred at 600C, when most of the radiation-induced defects had been annealed out. At between 650 and 900C, the diffusivity could be described by:

D(cm2/s) = 1.47 x 10-2exp[-1.27(eV)/kT]

V.M.Korol, A.V.Zastavny, M.N.Belikova: Fizika i Tekhnika Poluprovodnikov, 1975, 9[6], 1222