Seleniumnonstoichiometry in ZnSe under bivariant andmonovariant equilibriums was studied by a direct physical-chemical method. ZnSe single crystals grown from the melt and the vapor phase were used as starting materials. It was found out that at T > 720 K, overstoichiometric Se generatesmainly electrically neutral defects. ZnSe thin films (50-300 nm) were prepared by vacuum thermal sputtering on "cold" glass substrates. To control the nonstoichiometry of the films, a specially designed two-chamber evaporator was used. The nonstoichiometry, electrical properties and morphology of the ZnSe films were investigated under various preparation conditions. It was demonstrated that it is possible to form p-n junction by varying the nonstoichiometry of ZnSe nanofilms. (C) 2015 Elsevier B.V. All rights reserved.