Studies on the Microstructure and Optical Properties of Nanocrystalline ZnSe∶Cox Thin Film Prepared by Pulsed Laser Deposition
ZnSe∶Cox(x=0.1,0.3,0.5)nanocrystalline thin films were deposited on sapphire substrates by pulsed laser deposition at substrate temperature of 800 ℃.The crystal structure and optical properties of the thin films were investigated by X-ray diffraction,atomic force microscope,X-ray photoelectron spectroscopy,optical transmittance and photoluminescence spectra.The results show that the thin films with excellent crystalline quality and(111)preferred orientation are prepared.With increasing Co concentration,the crystalline quality,average transmittance and band gap of films decrease.There is a absorption band at the wavelength of about 700-850 nm in the film,which comes from the transition between 4A2(4F)→4T1(4P)energy levels of Co2+in the tetrahedral crystal field composed of surrounding Se2-.The films reach an overdoping state when the x value increases to 0.5,and the photoluminescence intensity of films decrease substantially due to the α-Co impurities un-incorporating into ZnSe lattice.
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