Preparation of nanocrystalline Mg doped CdSe thin films and their optical, photoluminescence, electrical and structural
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Preparation of nanocrystalline Mg doped CdSe thin films and their optical, photoluminescence, electrical and structural characterization Prashant K. Sahu1 · Ruby Das1 · Rajesh Lalwani1
Received: 4 June 2017 / Accepted: 20 August 2017 / Published online: 23 August 2017 © Springer Science+Business Media, LLC 2017
Abstract Phosphors used are mostly rare earth doped complex structures. A simple and unique material system of CdSe:Mg nanocrystalline thin films, which efficiently absorb UV (235 nm) and emit broad spectrum of greenyellow region has been prepared by chemical bath deposition method with average particle size of 52.3 nm, measured using AFM images. The optical absorption studies found that CdSe thin film has direct optical band gap, Eg of 2.62 eV that shows a blue shift of 0.88 eV compared to the bulk Eg value. Optical, electrical, structural and morphological properties were studied by UV–Vis–NIR spectrophotometer, photoluminescence (PL) emission spectra, dc two-probe method, X-ray diffraction (XRD), and atomic force microscope (AFM). Measured electrical resistivity decreased with increase of doping concentration. Activation energy was also calculated. The results confirm that the CdSe:Mg thin films are in the pure cubic phase. The magnesium concentrations also affect the nanocrystalline nature of the CdSe thin films. The optical band gap and surface roughness of CdSe thin films mostly decrease with 5% doping of Mg. The effect of Mg doping on refractive index, extinction coefficient and other optical parameters was also investigated.
* Ruby Das [email protected] Prashant K. Sahu [email protected] 1
Department of Applied Physics, Bhilai Institute of Technology, Durg, C.G. 491001, India
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1 Introduction Nanocrystalline (nc) thin films are an important category material that can find potential applications in photo electronic devices. Fundamental studies of cadmium selenide (CdSe), a well-known direct band gap II–VI semiconductor, have been reported for its applications in such fields as photodetectors, field-effect transistors (FETs), field emitters, solar cells, light-emitting diodes (LEDs), memory devices, biosensors and biomedical imaging [1–5]. Recently it has been found that size-tunable CdSe QDs have great potential in diagnosis of cancerous cells [6]. Due to strong quantum confinement effects and intrinsic dipole moments, nanocrystals have a large extinction coefficient that leads to rapid charge separation [7]. Inorganic semiconductor nanostructures find size and shape-dependent electrical and optical properties and can be processed with various methods. Doping is a widely used method to tailor the electrical and optical properties of semiconductors [2]. PL properties of the Doped semiconductor nanoparticles have been studied extensively because of their excellent luminescence properties. Alkaline earth aluminates (SrAl2O4) doped with rare earth ions show high chemical stability and bright emission in the visible region [8]. The ZnMgO nanophosphor film with 2
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