Mass spectrometry was used to study the vaporisation of super-stoichiometric Zn atoms from the oxide. From these results, the activation energy for Zn diffusion in ZnO at 300 to 800C was estimated to be 47kcal/mol.

A Mass Spectroscopic Method of Studying the Defect Structure of ZnO. Panasyuk, G.P., Danchevskaya, M.N., Kobozev, N.I.: Zhurnal Fizicheskoi Khimii, 1967, 41[3], 691-5