Structural and optical characterization of Zn0.95−xMg0.05CuxO nanoparticles

Abstract

In the present paper, Mg and Cu co-doped ZnO nanoparticles (Zn 0.95-x Mg 0.05 Cu x O) synthesized using SolGel method and their structural, optical properties were studied. Hexagonal wurtzite structure of ZnO was confirmed from XRD results. With Cu doping CuO related phase was formed without altering the crystal structure. The average crystallite size of ZnO decreased with increase of Mg and Cu co-doping. TEM results confirmed the nano size crystalline nature of ZnO nanoparticles. From FE-SEM micrographs, the particle sizes decreased and the morphology became less hexagonal with increase of Cu concentrations along with Mg in ZnO. The weaker and broadened E 2 (high) mode in Raman with increase of Cu doping concentrations may be attributed to wurtzite crystalline structure of ZnO is weakened. Thus, resulting to reduction of the growth induced strains which in good agreement with XRD results. From UV-Vis analysis, fundamental exciton absorption is observed at 377 nm for undoped ZnO. With addition of the dopants (Mg, Cu) the peak got blue shifted from 377 to 355 nm. The blueshift was attributed to the strains produced with dopants but not due to quantum confinement effect due to the sizes of the particles are not comparable of the Bohr atomic radius.

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“…44 Notably, the peak at 320 nm blue-shied to 302 nm for the NbPW-06 sample; this was likely not due to the quantum connement effect because the sizes of the NbPW-06 samples were not comparable with their Bohr atomic radii. 45 The TG analysis of the NbPW material is shown in Fig. S1.…”

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“…The green emission is endorsed to the near-band-edge emission of CdS and CdTeS, associated with the free-exciton recombination in CdS and CdTeS at room temperature. 36 The PL emission spectra of all these samples sensitized with different QDs on the surface of ZZ show that the optical properties are extremely sensitive to their defects densities and morphology. 3.6.…”

“…The ZnO PL spectrum consists of two parts, i.e., excitonic near band edge emission and the defects related deep level emission on the visible region. 36 The ZnO has UV excitonic emission peak exhibiting visible luminescence due to extrinsic and intrinsic defects. The origin of these different emissions, especially the green emission considered controversial.…”

“…The ZnO UV emission depends on some different factors, i.e., the direct transition from conduction band to valence band, transition of zinc interstitial (Zn i ) defect level to valence band, transition from the conduction band to zinc vacancy (V Zn ) which is a result of blue−green emission of the material, and transition from Zn i to V Zn . 36 The ZnO nanoflowers have a stronger emission peak at 390 nm and can be ascribed to band-to-band transition. However, it was observed that the strong and sharp UV band edge emission peak of the ZnO corresponds to the free excitons recombination process.…”