PROPERTIES OF ZNO LAYERS DEPOSITED BY PHOTO-ASSISTED SPRAY-PYROLYSIS

Layers of ZnO have been deposited onto glass substrates by ''photo-ass isted'' spray pyrolysis using zinc chloride and zinc acetate as precur sors in aqueous and non-aqueous solutions. The structure of these film s has been shown by reflection high energy electron diffraction (RHEED ) to be hexagonal, the crystallites exhibiting a pronounced preferred orientation with their (0002) planes lying parallel to the substrate. The transmission properties of layers deposited using an aqueous solut ion of zinc acetate were found to be superior. In their as-deposited f orm the films repeatedly exhibited carrier concentration, Hall mobilit y and resistivity values of similar to (1-2) X 10(17) cm(-3), similar to 0.1-0.2 cm(2) V-1 s(-1) and similar to 150-600 Ohm . cm respectivel y. However, following annealing at 400 degrees C for 15 min in forming gas (H-2 + N-2), these parameters improved to similar to 5 X 10(19) c m(-3), similar to 29 cm(2) V-1 s(-1) and similar to 1.5 X 10(-2) Ohm . cm respectively. Annealing did not change the transmittance but there was a noticeable improvement in the degree of preferred orientation. The considerable improvement in the electrical properties after anneal ing can be largely attributed to the increases in carrier concentratio n and mobility due to the change in stoichiometry and possibly a reduc tion in inter-granular potential barriers respectively.