Fabrication of ZnS/Porous Silicon Composite and Its Enhancement of Photoluminescence

Abstract

A ZnS thin film was electrodeposited on the surface of nanopores of porous silicon (PSi) without plugging of the nanopores. And the optical properties of the ZnS/PSi composites were investigated. The PSi was fabricated by anodization of n-Si (100) wafer in HF/EtOH/H 2 O solution under constant current conditions. The pore diameter and the porous layer depth of the PSi were 20-80 nm and 8-50 μm, respectively, and they are controlled by variation of the HF concentration and anodization time. Electrodeposition proceeded on the surface of the nanopores (pore diameter, 80 nm) of the PSi under galvanostatic conditions of 0.44-8.85 mA/cm 2 and the aqueous electrolyte solution contained ZnSO 4 , Na 2 S 2 O 3 and glycerol. The deposited ZnS plugged the nanopores at high current density, whereas at low current density, ZnS was deposited on the nanopore wall without plugging. The photoluminescence (PL) spectra due to the ZnS/PSi composites showed two separate peaks at 430 nm and 530 nm. The PL intensity decreased with increased current density because of the segregation of ZnS on the upper parts of the PSi nanopores. The PL intensity was also enhanced owing to the large surface area of the PSi.

Properties investigation of ZnS/porous silicon heterojunction for gas sensing

“…where B is constant, α is the absorption coefficient, hυ is photon energy, r takes ½ of direct transition and 2 of indirect transition. The results show, the optical energy gap decreases with number of spray and its values 3.26, 3.21, 3.1 eV for concentration (0.1 ,0.3 and 0.5M) respectively, which in good agreement with reported data for ZnS film deposited by other methods [28].…”