Charge transfer and optical properties of wurtzite-type ZnS/(CdS/ZnS)n (n=2, 4, 8) superlattices

ZnS/(CdS/ZnS)(n) (n = 2, 4, 8) superlattices were deposited on sapphire substrate by pulsed laser deposition (PLD) with alternate cadmium sulfide (CdS) and zinc sulfide (ZnS) crystals at 100 degrees C. The prepared samples with an average thickness of similar to 30 nm for ZnS layer and similar to 60 nm for CeIS layer have a wurtzitetype structure. Surface phonon of ZnS and multiple phonons modes for ZnS and CdS were observed from Raman spectra. PL spectra show a strong green emission at similar to 496 nm, two weak emission bands at similar to 400 and similar to 577 nm, where the emission band at 400 nm was attributed to the recombination of surface defects states to valence, the emission band at 577 nm as the recombination of Cd-i-V-cd centers, and the strong emission at similar to 496 nm is from the charge transfer of electrons from CdS electron to ZnS holes by excitation energy. (C) 2013 Elsevier Ltd. All rights reserved.