ZnS:Mn A.C. thin film electroluminescent (ACTFEL) display devices were fabricated at various phosphor deposition temperatures (T-s). The phosphor layer of all devices was formed by electron beam evaporation from ZnS:Mn powder with 1.2 wt.% Mn content. The amount of Mn actually present in the film was found to increase with T-s while the luminous efficiency of ACTFEL devices also increased with increasing T-s. increased phosphor efficiency was attributed to the higher Mn content and to the presence of larger phosphor fields in the higher deposition temperature devices. Crystallite perfection as measured by the full width at half maximum of X-ray diffraction peaks remained constant up to 300 degrees C, but decreased for higher T-s values.