Optical Study of High Quality c -ZnS Crystals for UV Photodiodes and Photoelectrochemical Applications

Abstract

Wide band gap semiconductors are proper candidates for manufacturing UV‐visible electronic devices, photocatalysts and power electronic components. Among them, II–VI ZnS has a high flexibility in tuning energy range as compared to ZnO because of a larger bandgap about 3.7 eV. In this work, a high‐quality {111}‐oriented ZnS crystal of zinc‐blende structure has been successfully grown by chemical vapor transport method using I2 as the transport agent. High‐resolution transmission electron microscopy verifies its crystallinity and crystal orientation, and energy dispersive X‐ray analysis identifies its stoichiometry. Due to the coupling between crystal field and spin orbital in the high quality solid, three band‐edge excitonic transitions of EA=3.745, EB=3.799 and EC=3.881 eV have been detected. An initial metal‐semiconductor‐metal (MSM) Schottky photodiode made by {111}‐ZnS crystal has been assessed. The dark resistivity is about 6.13 MΩ‐cm. Under the irradiation of a 266‐nm laser (power ∼1.6 mW), the photo‐resistivity change (i. e., Δρ/ρdark) reaches 88%. Photo‐catalytic ability of the {111}‐ZnS single crystal was also evaluated using Methyl‐blue degradation. The degradation (normalized concentration change) after 1 hour can reach C/C0≈ 0.47 under irradiation of Xe‐arc lamp. All the experimental results reveal high responsivity of the {111}‐ZnS photodiode and good photocatalytic function of the {111}‐oriented crystal photocatalyst operated in the UV range.

The Study of Near-Band-Edge Property in Oxygen-Incorporated ZnS for Acting as an Efficient Crystal Photocatalyst

“…Moreover, the cubic zinc sulfide (c-ZnS) can also act as heterogeneous photocatalysts for methyl blue degradation. 23 In spite of that, they were still lacking evidence about its photoconductivity (PC) capability as well as minor photogenerated carriers could stimulate the surface voltaic output through surface photovoltage (SPV) experiment. As a consequence, it would assist to predict for reasoning interaction between the electron–hole pair in the photodegradation of methylene blue (MNB) by the ZnS (1– x ) O x ( x = 0, 0.06, 0.12) series crystals.…”

“…These sample series emitted UV, purple, blue and green emission from photoluminescence spectra due to its defect state and also free exciton. Moreover, the cubic zinc sulfide (c-ZnS) can also act as heterogeneous photocatalysts for methyl blue degradation . In spite of that, they were still lacking evidence about its photoconductivity (PC) capability as well as minor photogenerated carriers could stimulate the surface voltaic output through surface photovoltage (SPV) experiment.…”