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김소아람,이상헌,김종수,김진수,Do Yeob Kim,Sung-O Kim,임재영 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.4
ZnO seed layers were deposited on a quartz substrate using the sol-gel method, and In-doped ZnO (IZO)nanorods with different In concentrations ranging from 0 to 2.0 at. % were grown on the ZnO seed layers by the hydrothermal method. The structural and optical properties of the ZnO and IZO nanorods were investigated using field-emission scanning electron microscopy, x-ray diffraction (XRD), and photoluminescence (PL). The ZnO and IZO nanorods grew well aligned on the surface of the quartz substrates. From the XRD data, it can be seen that the In doping is responsible for the distortion of the ZnO lattice. The PL spectra show near-band-edge emission and deep-level emission, and they also show that In doping significantly affects the PL properties of ZnO nanorods.
Seed-Layer-Free Hydrothermal Growth of Zinc Oxide Nanorods on Porous Silicon
김소아람,김민수,박형길,남기웅,윤현식,임재영 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.3
Zinc oxide (ZnO) nanorods were grown on porous silicon (PS) using hydrothermal synthesis without a metal catalyst or a seed layer. Scanning electron microscopy, x-ray diffraction, and temperature-dependent photoluminescence (PL) were carried out to investigate the structural and optical properties of the ZnO-PS sample. Most of the nanorods had an average diameter about of 120 nm and an average length of 5 μm, and were assembled into flower-like clusters where several nanorods were joined at a central point. In some cases, ZnO nanorods were merged in parallel bundles. The ZnO nanorods exhibited an overall compressive residual stress. The Zn-O bond length was 1.953 Å. ZnO-PS exhibited one PL peak in the ultraviolet (UV) range, and two peaks in the visible range. The UV and green emission peak were generated from the ZnO nanorods, while the red emission peak was attributed to the PS. The fitting parameters for Varshni’s empirical equation were α = 8 × 10−4 eV/K, β = 186 K, and E g(0) = 3.375 eV, and the thermal activation energy was about 32 meV.
김소아람,남기웅,윤현식,박형길,최현광,김종수,김진수,Do Yeob Kim,Sung-O Kim,임재영 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.4
Sol-gel dip-coating was used to prepare ZnO thin films with relaxed residual stress by lowering the deposition temperature from room temperature (25°C) to −25°C. The effect of deposition temperature on the structural, optical, and electrical properties of the films was characterized using scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL), ultraviolet-visible (UV-Vis) spectroscopy and reflectance accessory, and the van der Pauw method. All the thin films were deposited successfully onto quartz substrates and exhibited fibrous root morphology. At low temperature, the deposition rate was higher than at room temperature (RT) because of enhanced viscosity of the films. Further, lowering the deposition temperature affected the structural, optical, and electrical properties of the ZnO thin films. The surface morphology, residual stress, PL properties, and optical transmittance and reflectance of the films were measured, and this information was used to determine the absorption coefficient, optical band gap, Urbach energy, refractive index, refractive index at infinite wavelength, extinction coefficient, single-oscillator energy, dispersion energy, average oscillator wavelength, moments M−1 and M−3, dielectric constant, optical conductivity, and electrical resistivity of the ZnO thin films.
김소아람,남기웅,박형길,윤현식,이상헌,김종수,김진수,Do Yeob Kim,김성오,임재영 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.4
The structural and optical properties of the ZnO, Al-doped ZnO, Ga-doped ZnO, and In-doped ZnO nanorods were investigated using field-emission scanning electron microscopy, X-ray diffraction, photoluminescence (PL) and ultraviolet-visible spectroscopy. All the nanorods grew with good alignment on the ZnO seed layers and the ZnO nanorod dimensions could be controlled by the addition of the various dopants. For instance, the diameter of the nanorods decreased with increasing atomic number of the dopants. The ratio between the nearband- edge emission (NBE) and the deep-level emission (DLE) intensities (INBE/IDLE) obtained by PL gradually decreased because the DLE intensity from the nanorods gradually increased with increase in the atomic number of the dopants. We found that the dopants affected the structural and optical properties of the ZnO nanorods including their dimensions, lattice constants, residual stresses, bond lengths, PL properties, transmittance values, optical band gaps, and Urbach energies.
Temperature-dependent Photoluminescence of Boron-doped ZnO Nanorods
김소아람,박형길,남기웅,Hyunsik Yoon,김종수,Jinsoo Kim,Jeong-Sik Son,이상헌,임재영 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.11
Boron-doped ZnO (BZO) nanorods were grown on quartz substrates using hydrothermal synthesis, and the temperature-dependence of their photoluminescence (PL) was measured in order to investigate the origins of their PL properties. In the UV range, near-band-edge emission (NBE) was observed from 3.1 to 3.4 eV; this was attributed to various transitions including recombination of free excitons and their longitudinal optical (LO) phonon replicas, and donor-acceptor pair (DAP) recombination, depending on the local lattice configuration and the presence of defects. At a temperature of 12 K, the NBE produces seven peaks at 3.386, 3.368, 3.337, 3.296, 3.258, 3.184, and 3.106 eV. These peaks are, respectively, assigned to free excitons (FX), neutral-donor bound excitons (DoX), and the first LO phonon replicas of DoX, DAP, DAP-1LO, DAP-2LO, and DAP-3LO. The peak position of the FX and DAP were also fitted to Varshni’s empirical formula for the variation in the band gap energy with temperature. The activation energy of FX was about ~70 meV, while that of DAP was about ~38 meV. We also discuss the low temperature PL near 2.251 eV, related to structural defects.