Enhanced violet emission from ZnS nanowires annealed in an oxygen atmosphere

The influence of thermal annealing in an oxygen atmosphere on the photoluminescence properties of ZnS nanowires has been investigated. ZnS nanowires with the diameters of a few tens of nanometers and the lengths of a few hundreds of micrometers were synthesized by thermal evaporation of ZnS powders on Au-coated Si substrates. The ZnS nanowires had an emission band centered at approximately 430 nm in the violet region. The intensity of the violet emission was enhanced significantly by annealing the ZnS nanowires at 500 °C in an oxygen atmosphere for 45 min. The possible sources for the violet emission enhancement by annealing in an O2 atmosphere are as follows: (1) the Zn2+ vacancies formed in the nanowires. (2) the oxygen impurity atoms, which have diffused from the O2 annealing atmosphere into the nanowires.