Photoluminescent Enhancement by Effect of Incorporation Nickel in ZnO Films Grown

Microstructured films of undoped zinc oxide (ZnO) and ZnO doped with nickel (ZnO:Ni) were grown by hot filament chemical vapor deposition (HFCVD) technique on Si (100) substrates at 500 °C. Pellets of ZnO and ZnO:NiO as oxidant agenst were used. A shift to the right around 0.17 degree of the X-Ray Diffraction pattern of the ZnO:Ni film was observed with respect to undoped ZnO films. Morphologically by Scanning Electron Microscopy was noticed a Core-Shell type growth in ZnO undoped and a nanostructured type (Nano-wire) in ZnO doped with Ni. Photoluminescence measurements showed an increase in the intensity of the green emission band of ZnO:Ni. It was attributed to defects of oxygen vacancies (VO), zinc vacancies (VZn), zinc interstitials (Zni), oxygen interstitials (Oi), and oxygen vacancies complex (VO complex) in the structure of the film. The incorporation of Ni atoms in the ZnO structure stresses the crystal lattice, leaving behind a large number of surface defects that increase the emission of PL.

Grown and Characterization of ZnO Aligned Nanorod Arrays for Sensor Applications

ZnO nanorods are promising materials for many applications, in particular for UV detectors. In the present paper, the properties of high crystal quality individual ZnO nanorods and nanorod arrays grown by the self-catalytic CVD method have been investigated to assess their possible applicationsfor UV photodetectors. X-ray diffraction, Raman spectroscopy and cathodoluminescence investigations demonstrate the high quality of nanorods. The nanorod resistivity and carrier concentration in dark is estimated. The transient photocurrent response of both as grown and annealed at 550 °C nanorod array under UV illumination pulses is studied. It is shown that annealing increases the sensitivity and decreases the responsivity that is explained by oxygen out-diffusion and the formation of near surface layer enriched with oxygen vacancies. Oxygen vacancy formation due to annealing is confirmed by an increase of green emission band intensity.

Mn2+/Mn4+ co-doped LaM1-xAl11-yO19 (M = Mg, Zn) luminescent materials: electronic structure, energy transfer and optical thermometry properties

Dual-emitting from manganese ion doped LaM1-xAl11-yO19 (M = Mg, Zn) phosphors were prepared by Mn2+ substituting Zn2+/Mg2+ and Mn4+ replacing Al3+. The LaM1-xAl11-yO19:xMn2+,yMn4+phosphor present narrow green emission band of the...

Experimental and DFT Study of the Photoluminescent Green Emission Band of Halogenated (−F, −Cl, and −Br) Imines

The morphological, optical, and structural changes in crystalline chiral imines derived from 2-naphthaldehyde as a result of changing the −F, −Cl, and −Br halogen (−X) atoms are reported. Scanning electron microscopy (SEM), optical absorption, photoluminescence (PL), and powder X-ray diffraction (XRD) studies were performed. Theoretical results of optical and structural properties were calculated using the PBE1PBE hybrid functional and compared with the experimental results. Differences in surface morphology, absorbance, XRD, and PL of crystals were due to the change of halogen atoms in the chiral moiety of the imine. Absorption spectra exhibited the typical bands of the naphthalene chromophore located in the ~200–350 nm range. Observed absorption bands in the UV region are associated with π→π* and n→π* electronic transitions. The band gap energy was calculated using the Tauc model. It showed a shift in the ~3.5–4.5 eV range and the crystals exhibited different electronic transitions associated with the results of absorbance in the UV region. XRD showed the monoclinic→orthorhombic crystalline phase transition. PL spectra displayed broad bands in the visible region and all the samples have an emission band (identified as a green emission band) in the ~400–750 nm range. This was associated with defects produced in the morphology, molecular packing, inductive effect and polarizability, crystalline phase transition, and increase in size of the corresponding halogen atoms; i.e., changes presumably induced by −C−X…X−, −C−X…N−, −C−N…π, and −C−X…π interactions in these crystalline materials were associated with morphological, optical, and structural changes.

PHOTOLUMINESCENCE EMISSION OF Cu DOPED ZnS MICROSTRUCTURES SYNTHESIZED BY THERMAL EVAPORATION

Cu doped ZnS microstructures were prepared by the thermal evaporation method using ZnS powder and CuCl2.2H2O powder as precusor materials. The microstructures was characterized by using X-ray diffraction (XRD) analysis. The XRD studies indicated that there are two phases (ZnS and ZnO) at the undoped sample, but most of the samples are only having wurtzite (hexagonal) phase of ZnS after doping. The photoluminescence emission and photoluminescence excitation of ZnS and Cu2+ doped ZnS microstructures have been studied. The photoluminescence excitation spectra of ZnS microstructures is present around 374 nm. After doping of Cu2+ ion the absorption wavelength shifted towards the lower wavelength, this blue shift in the absorption edge is a measure of increased band gap. The emission spectrum of pure ZnS has a green emission band centred at around 520 nm. After doping with Cu2+ ion the luminescence centers were transferred to 516 nm and a strong blue peak at 440 nm appears. The reasons of these will be discussed in this paper.

Preparation and characterization of ZnS nanoparticles prepared by hydrothermal method

ZnS nanoparticles were prepared by hydrothermal method using zinc nitrate [Zn(NO[Formula: see text] ⋅ 6H2O] and thiourea [SC(NH[Formula: see text]] as sources of Zn[Formula: see text] and S[Formula: see text] ions and cetyltrimethyl ammonium bromide [CH3(CH2)[Formula: see text]N[Formula: see text](CH3)3 ⋅ Br[Formula: see text]; CTAB] as a surface active agent. The structural, surface morphology and optical properties of ZnS nanoparticles as a function of growth temperature were investigated. The studies show that ZnS nanoparticles have high transmittance over 70% in the visible light range of 400–800 nm, and it has a strong green emission band at about 520 nm which originates from the recombination of electrons from the energy level of sulfur vacancies with the holes from the energy level of zinc vacancies. With the increase of the growth temperature, the XRD peak intensity and the size of ZnS nanoparticles increase, while the green emission intensity firstly increases and then decreases.