RF sputter deposition of SrS:Eu and ZnS:Mn thin film electroluminescent phosphors

The radio-frequency (rf) sputter deposition of thin film electroluminescent (TFEL) materials was studied. Thin films of strontium sulfide doped with europium (SrS:Eu) and zinc sulfide doped with manganese (ZnS:Mn) were RF sputter deposited at different conditions. Photoluminescent and electroluminescent behaviors of these films were examined.; Photoluminescent active, crystalline films of SrS:Eu were deposited at temperatures from {dollar}{bsol}rm 300{bsol}sp{bsol}circ C{dollar} to {dollar}{bsol}rm 650{bsol}sp{bsol}circ C.{dollar} The best temperature was {dollar}{bsol}rm 400{bsol}sp{bsol}circ C,{dollar} where a PL efficiency of 35% was achieved. Films were deposited at two power levels (90 and 120 watts) and five {dollar}{bsol}rm H{bsol}sb2S{dollar} concentrations (0.6%, 1.3%, 2.4%, 4.0% and 5.3%). The {dollar}{bsol}rm H{bsol}sb2S{dollar} concentration affected the crystallinity of the films and the PL performance. Lower {dollar}{bsol}rm H{bsol}sb2S{dollar} concentrations resulted in films with smaller crystallite sizes and poorer PL performance. Increased {dollar}{bsol}rm H{bsol}sb2S{dollar} concentrations increased the PL intensity and the overall spectra resembled that of an efficient SrS:Eu powder.; Although there was a correlation between crystallinity and PL performance other factors such as europium concentration, distribution, and local environment also influence PL performance. Analytical results suggested that, although a film may be crystalline and have the correct europium concentration, unless the europium is in the correct localized environment, optimum PL response will not be achieved. Increased {dollar}{bsol}rm H{bsol}sb2S{dollar} concentrations produced films with europium located in optimum locations.; Contrary to vacuum or chemical vapor deposited films, the sputter deposited films showed no trailing edge emission during electroluminescence. A suggested reason for this lack of a trailing edge emission in these films is that the sputter deposition process produces phosphor-insulator interfaces without shallow trap states.; A statistical design of experiments approach was implemented for the sputter deposition of ZnS:Mn. The effects of four factors (substrate temperature, chamber pressure, power to the target, and {dollar}{bsol}rm H{bsol}sb2S{dollar} concentration) on three responses (deposition rate, stoichiometry, and PL performance) were studied. A 1/2 fractional factorial showed that each of the factors had a significant influence on at least one response. A large experimental error with subsequent Box-Behnken experiments, however, indicated that some uncontrolled factor was influencing the quality of the films. The large experimental error prevented the development of reliable experimental models based on the Box-Behnken results.