Zinc Sulfide Sputtering Targets
Zinc sulfide is an inorganic compound with the chemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the mineral sphalerite.
Zinc sulfide is an important wide band gap semiconductor material with extensive potential applications, such as flat-panel displays, sensor, light-emitting diodes, photodetectors and solar cells. In the important application of photovoltaics, zinc sulfide can be used as buffer layer material of CuInGaSe2 (CIGS), Cu2ZnSnS4 (CZTS) thin-film solar cells. Compared to cadmium sulfide used commonly as buffer layer material, zinc sulfide has some advantages which are nontoxic, abundant, cheap, lattice matched with CIGS or CZTS absorber, possessing wide band gap. Zinc sulfide is a direct band gap n type semiconductor. The band gap of zinc sulfide is in the range of 3.2 ~ 3.9 eV, while the band gap of cadmium sulfide is only about 2.45eV. The wide band gap of zinc sulfide enables high energy incident photons to reach the window-absorber junction, enhancing the blue response of the photovoltaic cells and thus contributes to a better cell performance.
The main fabrication methods of zinc sulfide films involve chemical bath depositio, chemical vapor deposition, molecular beam epitaxy, thermal evaporation and RF magnetron sputtering. Among these fabrication methods, magnetron sputtering technique has some advantages such as easier controllability of the deposition parameters, high film growth rate, compatibility with the sputtering depositions of absorber and window layer and thus beneficial to industrial production of solar cells.
Thin film solar cells with high efficiency require thin films fabricated with high quality. Annealing is one method used often to improve film quality.