Tunable blue and orange emissions of ZnS:Mn thin films deposited on GaN substrates by pulsed laser deposition

ZnS:Mn thin films have been grown on GaN substrates by pulsed laser deposition, and their structures and optical properties have been investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL), and electron paramagnetic resonance. The ZnS:Mn thin films have a cubic structure that is oriented mainly along the (1 1 1) plane. The crystal quality was optimized by varying the deposition conditions. Room temperature PL measurements with a 325 nm excitation source show that there are three emission bands located at 434 nm, 465 nm and ~600 nm. The intensity ratio of the blue emission bands (434 nm, 465 nm) to the orange (600 nm) was determined by the deposition conditions. The broad orange emission consisted of two emission bands centered at 590 and 615 nm, and it exhibited a red shift for measurement temperatures between 5 and 70 K, followed by a blue shift at temperatures up to 300 K. The tunable blue and orange dual color emissions make this material a candidate for use as a warm white lighting emitting device.