Lasing from ZnO Nanocrystals in ZnO-ZnS Microbelts
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We present an investigation of the morphology, structure, composition, chemical state and optical properties of ZnO-ZnS microbelts grown by the thermal evaporation method. It is found that the ZnO-ZnS microbelts are composed of ZnS and ZnO nanocrystals with high crystalline quality. Under optical pumping from a Nd:YAG laser at 266 nm, stimulated lasing emissions from ZnO nanocrystals are observed with a threshold as low as 10 mJ/cm2. The low lasing threshold of ZnO nanocrystals is interpreted as a result of the modification of ZnO surfaces with a ZnS layer that efficiently passivates the surface defects and reduces nonradiative Auger recombination.
KeywordsZnO nanocrystal ZnO-ZnS microbelts thermal evaporation lasing
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This work was financially supported by the National Foundation for Science and Technology Development (NAFOSTED), Vietnam, under Project No. 103.06-2011.06. The XPS measurements have been carried out at the Green Mobility Collaborative Research Center (GREMO), Nagoya University, Japan.