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 550 to 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 650 to 900C, the diffusivity could be described by:

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

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