Multiphonon Raman scattering and photoluminescence studies of CdS nanocrystals grown by thermal evaporation. (March 2018)

• Record Type: Journal Article
• Authors: Farid, Sidra; Stroscio, Michael A.; Dutta, Mitra
• Is Part Of: Superlattices and microstructures. Volume 115(2018)
• Page Start: 204
• Page End: 209
• Publication Date: 2018-03
• Subjects: Superlattices as materials -- Periodicals; Microstructure -- Periodicals; Semiconductors -- Periodicals; Superréseaux -- Périodiques; Microstructure (Physique) -- Périodiques; Semiconducteurs -- Périodiques; 621.38152
• DOI: 10.1016/j.spmi.2018.01.024
• Languages: English
• ISSNs: 0749-6036

Abstract

Abstract: Thermal evaporation growth technique is presented as a route to grow cost effective high quality CdS thin films. We have successfully grown high quality CdS thin films on ITO coated glass substrates by thermal evaporation technique and analyzed the effects of annealing and excitation dependent input of CdS thin film using Raman and photoluminescence spectroscopy. LO phonon modes have been analyzed quantitatively considering the contributions due to anneal induced effects on film quality using phonon spatial correlation model, line shape and defect state analysis. Asymmetry in the Raman line shape towards the low frequency side is related to the phonon confinement effects and is modeled by spatial correlation model. Calculations of width (FWHM), integrated intensity, and line shape for the longitudinal (LO) optical phonon modes indicate improved crystalline quality for the annealed films as compared to the as grown films. With increase in laser power, intensity ratio of 2-LO to 1-LO optical phonon modes is found to increase while multiple overtones upto fourth order are observed. Power dependent photoluminescence data indicates direct band-to-band transition in CdS thin films. Highlights: Thermal evaporation technique is presented as a route to grow cost effective high quality CdS thin films. Raman peaks upto fourth order for the CdS nanocrystals have been reported. Spatial correlation model fitting achieved and asymmetry in the LO phonon modes line shape is observed. Direct band-to-band transition is reported using power dependent photoluminescence studies. Major applications in optoelectronic devices and can lead to enhanced device performances.