Photoluminescence and resonant Raman scattering from ZnO-opal structures

Abstract

Structural transition in II-VI nanofilms: Effect of molar ratio on structural, morphological, and optical properties J. Appl. Phys. 111, 113510 (2012) Emission from a dipole-forbidden energy state in a ZnO quantum dot induced by a near-field interaction with a fiber probe Appl. Phys. Lett. 100, 223110 (2012) Effect of Lorentz local field for optical second order nonlinear susceptibility in ZnO nanorod J. Appl. Phys. 111, 103112 (2012) A comparative study of ultraviolet photoconductivity relaxation in zinc oxide (ZnO) thin films deposited by different techniques J. Appl. Phys. 111, 102809 (2012) Additional information on J. Appl. Phys. We study photoluminescence ͑PL͒ of ZnO-opal structures excited by a 351.1 nm laser line. The structures were fabricated by infiltration of ZnO from an aqueous solution of zinc nitrate into opal matrices. The emission spectrum of thick ZnO layers grown on the surface of bulk opals exhibits narrow PL bands associated with the recombination of bound and free-excitons. The free-exciton lines are discussed taking into account the polariton phenomena. The width of the excitonic lines ͑2-3 meV͒ along with their energy position is indicative of high quality and strain-free state of the layer. The emission from ZnO crystallites embedded into bulk opal is dominated by near band gap luminescence, a weak quantum confinement effect being observed for crystallites with sizes around 50 nm. Thin ZnO films grown on single-layer opals exhibit enhanced resonant Raman scattering, phonon confinement effects, and surface-related modes. Strong exciton-LO phonon and exciton-Fröhlich mode coupling in ZnO nanostructures is deduced from the analysis of multiphonon excitonic resonant Raman scattering.

Enhanced Resonant Raman Scattering and Electron−Phonon Coupling from Self-Assembled Secondary ZnO Nanoparticles

“…41 The weak peak, which is contributed to the E 2 (high) mode around 437 cm -1 , is almost imperceptible as a result of other stronger RRS peaks. Multiphonon scattering processes also have been previously reported for single crystalline bulk ZnO 42 and recently for ZnO films, 43 ZnO opal structures, 44 and ZnO nanowires 45,46 but rarely mentioned for ZnO NPs. From the RRS spectra, it is remarkable that the intensities of the first-order Raman mode and its overtones are enhanced in the as-grown ZnO NPs compared with the postannealed samples.…”

Raman spectroscopy of optical phonon confinement in nanostructured materials

“…79 -83 Thin ZnO films grown on SiO 2 opal structure have shown resonance enhancement of the 3-LO Raman peak along with evidence of Frohlich vibrational modes. 79 Excitation of 20-nm ZnO nanoparticles (synthesized using a wet chemical method) with the 325-nm UV line exhibited a red-shift (as much as 14 cm 1 ) of 1-LO phonon wavenumber as a function of laser power. 81 This was attributed to the laser heating of the nanoparticles to temperatures as high as 1000 K, as estimated form the anharmonicity of the phonons.…”

Dominant ultraviolet-blue photoluminescence of ZnO embedded into synthetic opal

“…Preliminary studies concerning optical properties of ZnO nanocrystals inside the synthetic opal obtained by using the spray pyrolysis method have been reported [17][18][19][20][21][22][23]. Despite the high density of crystal defects, a strongly dominant UV-blue emission in the PL spectra of polycrystalline ZnO was observed.…”