Fabrication and characterization of ZnS:(Cu,Al) thin film phosphors on glass substrates by pulsed laser deposition

We fabricated ZnS:(Cu,Al) thin film phosphors on glass substrates by pulsed laser deposition (PLD) using a KrF 248 nm laser in a H2S gas flow. Firstly, we investigated effects of annealing temperature, stress and crystallinity on photoluminescence properties of powder samples. For thin films, photoluminescence intensity increased with increasing the substrate temperature up to 700 °C and then decreased. The former increase is attributed to improvement of crystalline quality and strain, while the latter degradation is attributed to reduction of the Cu acceptors. Intense photoluminescence is observed under an ambient light when excited by 325 nm monochromated light from a fluorescence spectrophotometer. It was confirmed that the PLD process stabilized the wurtzite structure, which is not stable in bulk samples at the thermal equilibrium.