Metal–Semiconductor–Metal UV Detectors Using Transferrable Amorphous and Crystalline Zinc-Tin-Oxide Microsphere Monolayers

Metal–semiconductor–metal UV photodetectors consisting of transferable zinc-tin-oxide (ZTO) microsphere (MS) monolayers with different phases and sizes are reported. From the experimental results, the crystallized Zn2SnO4 (c-ZTO)-MS-monolayer-based photodetectors present higher performance than amorphous ZnSnO3 (a-ZTO)-based photodetectors. The external quantum efficiencies of the a-ZTO- and c-ZTO-MS-based UV photodetectors are 16.7% (at 320 nm) and 580.9% (at 310 nm), respectively. Moreover, the UV-to-visible rejection ratios of the a-ZTO and c-ZTO are 20 (320 nm/400 nm) and 1484 (310 nm/400 nm), respectively, indicating that both fabricated ZTO MS UV photodetectors present great visible-blind properties. To further improve the optoelectronic device performance, the c-ZTO-MS-based UV photodetector is optimized using various sphere diameters, namely, 0.79, 0.99, 1.24, and 1.51 μm. The best photodetecting properties are obtained for the 1.24 μm c-ZTO MS detector, showing a 51.1-fold improvement in photocurrent compared with the lowest level c-ZTO-based detector. These results are attributed to the different oxygen-related defect ratios in the ZTO MSs. The reported transferable ZTO-MS-monolayer-based optoelectronic devices have the potential for novel optoelectronic applications.