Using eco-friendly, safety and well thermal stability oxides as the materials for this study. The Co-doped zinc ferrite targets are single-phase with various doping concentrations, and their thin films were deposited by radio-frequency (RF) sputtering. Oxygen vacancies were created when Co2+ ions occupy the octahedral sites in the zinc ferrite structure, which made the 5 at % Co-doped zinc ferrites an n-type semiconductor material. The conduction energy band and the valence energy band versus the vacuum level were further obtained to be −3.6 and −5.73 eV from UPS analyses with a Fermi energy of −3.86 eV versus the vacuum level. The n-type 5 at % Co-doped zinc ferrite thin films were selected to fabricate the trilayer photodetectors because of their higher photoluminescence intensity and a lower optical band gap of 2.01 eV. The photodetector performance was optimized using Co-doped ZnFe2O4 annealed at 400 °C in air for 4 h. The photosensitivity of Co-doped ZnFe2O4 photodetectors reached up to 181, which is evidently greater than previously reported ZnFe2O4 nanotube photodetectors and most metal oxide based photodetectors. A noticeably fast photo switching response of rise time = 10.6 ms and fall time = 9.9 ms is also obtained under 630 nm illumination. Co-doped ZnFe2O4 thin films show promising potential for light-harvesting and imaging applications. This device also can be fabricated with low cost and good reproducibility for extended applications.
(source: https://pubs.acs.org/doi/full/10.1021/acsami.0c20487)