Structural evolution and optical properties of oxidized ZnS microrods

• High quality optically defect free ZnS microrods were synthesized in large scale.
• The structural evolution and changes in optical emission upon oxidation were disclosed.
• Luminescence of oxygen-related defect can be tuned using oxidation temperature.
• The initial ZnS microrods can be converted into ZnS/ZnO heterostructure.
• Porous ZnO microrods with negligible defect emissions were achieved.

In this study, we present a simple and versatile way to growth and modify photoemission of high quality ZnS microrods by thermal evaporation method in combination with post oxidation in oxygen environment. The as-grown ZnS microrods show strong near edge luminescence doublets at room temperature indicating the high crystalline quality. Using ultrahigh-resolution scanning electron microscope integrated with energy microanalysis and cathodoluminescence capacity we elucidate the effect of oxidation temperature on microstructure surface, chemical composition and emission spectra of ZnS microrods. Under appropriate oxidation condition, the initial high quality ZnS microrods can be converted into ZnS/ZnO microrod heterostructures or optically active porous ZnO microrods. More particularly, we demonstrate that the emission wavelength of an oxygen-related defect could be tuned in between optical band-gap of ZnS and ZnO upon increasing the oxidation temperature. This research introduces a simple approach to synthesize and tune optical property of high quality ZnS crystals.

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