Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 10, Issue 34, Pages 28736-28744Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.8b06192
Keywords
ZnO/ZnS core/shell nanowire; piezotronic effect; piezo-phototronic effect; crystal-structure dependence; photosensing
Funding
- GIST Research Institute (GRI) Project through Gwangju Institute of Science and Technology
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We report the crystal-structure-dependent piezotronic and piezo-phototronic effects of ZnO/ZnS core/shell nanowires (CS NWs) having different shell layer crystalline structures. The wurtzite (WZ) ZnO/WZ ZnS CS NWs showed higher electrical transport and photosensing properties under external strain than the WZ ZnO/zinc blende (ZB) ZnS CS NWs. The WZ ZnO/WZ ZnS CS NWs under a compressive strain of -0.24% showed 4.4 and 8.67 times larger increase in the output current (1.93 x 10(-4) A) and photoresponsivity (8.76 x 10(-1) A/W) than those under no strain. However, the WZ ZnO/ZB ZnS CS NWs under the same strain condition showed 3.2 and 2.16 times larger increase in the output current (1.13 x 10(-4) A) and photoresponsivity (2.16 x 10(-1) A/W) than those under no strain. This improvement is ascribed to strain-induced piezopolarization charges at both the WZ ZnO NWs and the grains of the WZ ZnS shell layer in WZ ZnO/WZ ZnS CS NWs, whereas piezopolarization charges are induced only in the ZnO core region of the WZ ZnO/ZB ZnS CS NWs. These charges can change the type-II band alignment in the ZnO and ZnS interfacial region as well as the Schottky barrier height at the junction between the semiconductor and the metal, thus facilitating electrical transport and reducing the recombination probability of charge carriers under UV irradiation.
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