Preparation of thin CuAlSe2 films by annealing of stacked Cu/Al/Se/Al... layers, study of deposition conditions

Thin layers of Cu/Al/Se/Al/Cu/Al/Se/.../Al/Se sequentially deposited have b een annealed half an hour at 855 K. CuAlSe2 thin films crystallized in the chalcopyrite structure are obtained, The films being contaminated by oxygen , the experimental deposition conditions of the aluminum layer have been im proved in order to decrease the atomic concentration of oxygen below 5 at%. Such results can be obtained in vacuum of 10(-4) Pa, when the aluminum dep osition rate is 1 nm/s and when the layer is immediately covered after depo sition. Films obtained in such a way are nearly stoichiometric with lattice parameters in accordance with the expected ones (a = 0.5607 nm, c = 1.0986 nm). As shown by scanning electron microscope the averaged crystallite dia meter is about 0.6 mu m. The forbidden gap deduced from optical measurement s is evaluated at 2.67 eV which corresponds to single crystal value.