title: Spectral investigations on undoped and Cu²⁺ doped ZnO-CdS composite nanopowders.
abstract: Undoped and Cu(2+) doped ZnO-CdS composite nanopowders were synthesized by simple chemical precipitation method. Structural and spectroscopic properties of the prepared samples have been characterized by XRD, SEM with EDS, TEM, FT-IR, UV-Vis, EPR and Photoluminescence studies. X-ray diffraction pattern contains a series of peaks corresponds to hexagonal phase of ZnO and CdS. The average crystallite sizes of undoped and Cu(2+) doped samples are determined and are in the range of 25-30 nm. SEM and TEM micrographs reveal that the samples show spherical like structures with little agglomeration. FT-IR spectra show the fundamental mode of vibrations of ZnO at 515 cm(-1), CdS at 621 cm(-1) and other functional groups. Optical absorption spectrum of Cu(2+) doped sample consists of three bands at 665, 823 and 1192 nm attributed to the transitions (2)B1g→(2)Eg, (2)B2g and (2)A1g respectively. Crystal field and tetragonal field parameters are evaluated as Dq=1214, Ds=1610 and Dt=389 cm(-1). From EPR, spin-Hamiltonian and hyperfine splitting parameters are evaluated for Cu(2+) doped sample as g‖=2.3391, g⊥=2.0550 and A‖=130×10(-4) cm(-1), A⊥=36×10(-4) cm(-1). The optical and EPR data suggests that Cu(2+) entered into host lattice as tetragonally distorted octahedral site symmetry. PL spectra consists two emission bands at 367, 380 nm in UV region. A sharp blue emission peak at 425 nm and a broad green emission peak in the range of 450-570 nm are observed. The enhanced visible emission is observed after doping.
authors.affiliation: Department of Physics, University College of Sciences, Acharya Nagarjuna University, Nagarjuna Nagar 522510, A.P., India.
authors.forename: G Thirumala
authors.initials: GT
authors.lastname: Rao
authors.affiliation: Department of Physics, University College of Sciences, Acharya Nagarjuna University, Nagarjuna Nagar 522510, A.P., India.
authors.forename: B
authors.initials: B
authors.lastname: Babu
authors.affiliation: Department of Physics, University College of Sciences, Acharya Nagarjuna University, Nagarjuna Nagar 522510, A.P., India.
authors.forename: R Joyce
authors.initials: RJ
authors.lastname: Stella
authors.affiliation: Department of Physics, University College of Sciences, Acharya Nagarjuna University, Nagarjuna Nagar 522510, A.P., India.
authors.forename: V Pushpa
authors.initials: VP
authors.lastname: Manjari
authors.affiliation: Department of Physics, University College of Sciences, Acharya Nagarjuna University, Nagarjuna Nagar 522510, A.P., India. Electronic address: rvssn@yahoo.co.in.
authors.forename: R V S S N
authors.initials: RV
authors.lastname: Ravikumar
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D003460:Crystallization; D004578:Electron Spin Resonance Spectroscopy; D049449:Luminescence; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D011208:Powders; D013052:Spectrometry, X-Ray Emission; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013440:Sulfides / Q000737:chemistry*; D013696:Temperature; D014961:X-Ray Diffraction; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D011208:Powders; D013440:Sulfides; C034939:cadmium sulfide; D003300:Copper; D015034:Zinc Oxide
keywords: Composite nanopowder; Electron paramagnetic resonance; Photoluminescence; Semiconductor; ZnO–CdS