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Abstract:
Semiconducting heterostructures with type-II band structure have attracted much attention due to their novel physical properties and wide applications in optoelectronics. Herein, we report, for the first time, a controlled synthesis of type-II ZnS/SnO2 heterostructured ribbon composed of SnO2 nanoparticles that uniformly cover the surface of ZnS ribbon via a simple and versatile thermal evaporation approach. Structural analysis indicated that the majority of SnO2 nanoparticles have an equivalent zone axis, i.e., <−313> of rutile SnO2, which is perpendicular to ±(2−1−10) facets (top/down surfaces) of ZnS ribbon. For those SnO2 nanoparticles decorated on ±(01−10) facets (side surfaces) of ZnS ribbon, an epitaxial relationship of (01−10)ZnO//(020)SnO2 and [2−1−10]ZnO//[001]SnO2 was identified. To explore their electronic and optoelectronic properties, we constructed field-effect transistors from as-prepared new heterostructures, which exhibited an n-type characteristic with an on/off ratio of [similar]103 and a fast carrier mobility of [similar]33.2 cm2 V-1 s-1. Owing to the spatial separation of photogenerated electron–hole pairs from type-II band alignment together with the good contacts between electrodes and ribbon, the resultant photodetector showed excellent photoresponse properties, including large photocurrent, high sensitivity (external quantum efficiency as high as [similar]2.4 × 107%), good stability and reproducibility, and relatively fast response speed. Our results suggest great potential of ZnS/SnO2 heterostructures for efficient UV light sensing, and, more importantly, signify the advantages of type-II semiconducting heterostructures for construction of high-performance nano-photodetectors.
