Oxygen codoping of ZnS:Tb,F electroluminescent thin film

Thin films of ZnS:Tb,F were sputter deposited from a ZnS:TbF3 target in an oxygen-argon ambient. The highest electroluminescent brightness (82 cd/m2 at 60 Hz) was measured from ZnS:Tb,F films with a 3.6 at% oxygen concentration. Oxygen concentrations above or below this concentration resulted in sharp decreases in brightness (56 cd/m2 at 2.2 at% oxygen, and 42 cd/m2 at 8.1 at% oxygen). The brightness improvement by oxygen codoping between 0 and 3.6 at% results from increased conduction charge with increasing oxygen concentrations. The brightness decrease for oxygen >3.6 at% is attributed to decreases of both excitation and radiative efficiencies. Improved electroluminescent brightness from oxygen codoping during sputter deposition of ZnS:Tb,F films was equivalent to the improvement observed in films deposited from a ZnS:TbOF target.