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Yim, Kwang Gug,Kim, Min Su,Leem, Jae-Young American Scientific Publishers 2013 Journal of nanoscience and nanotechnology Vol.13 No.5
<P>ZnO nanostructures were grown on Si (111) substrates by a hydrothermal method. Prior to growing the ZnO nanostructures, ZnO seed layers with different post-heat temperatures were prepared by a spin-coating process. Then, the ZnO nanostructures were annealed at 500 degrees C for 20 min under an Ar atmosphere. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out at room temperature (RT) to investigate the structural and optical properties of the as-grown and annealed ZnO nanostructures. The surface morphologies of the seed layers changed from a smooth surface to a mountain chain-like structure as the post-heating temperatures increased. The as-grown and annealed ZnO nanostructures exhibited a strong (002) diffraction peak. Compared to the as-grown ZnO nanostructures, the annealed ZnO nanostructures exhibited significantly strong enhancement in the PL intensity ratio by almost a factor of 2.</P>
As과 Ga 빔 조사에 의해 세척된 Si(100) 기판 위에 GaAs 에피층 성장과 RHEED 패턴
임광국(Kwang Gug Yim),김민수(Min Su Kim),임재영(Jae-Young Leem) 한국표면공학회 2010 한국표면공학회지 Vol.43 No.4
The GaAs epitaxial layers were grown on Si(100) substrates by molecular beam epitaxy(MBE) using the two-step method. The Si(100) substrates were cleaned with different surface cleaning method of vacuum heating, As-beam, and Ga-beam at the substrate temperature of 800℃. Growth temperature and thickness of the GaAs epitaxial layer were 800℃ and 1 ㎛, respectively. The surface structure and epitaxial growth were observed by reflection high-energy electron diffraction(RHEED) and scanning electron microscope(SEM). Just surface structure of the Si(100) substrate cleaned by Ga-beam at 800oC shows double domain (2 × 1). RHEED patterns of the GaAs epitaxial layers grown on Si(100) substrates with cleaning method of vacuum heating, As-beam, and Ga-beam show spot-like, (2 × 4) with spot, and clear (2 × 4). From SEM, it is found that the GaAs epitaxial layers grown on Si(100) substrates with Ga-beam cleaning has a high quality.
김민수,Kwang Gug Yim,Do Yeob Kim,Soaram Kim,Giwoong Nam,남기웅,Sung-O Kim,김진수,김종수,손정식,임재영 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.1
Catalyst- and seed layer-free zinc oxide (ZnO) thin films were grown on porous silicon (PS) by a hydrothermal method. Atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD),Raman spectroscopy, and photoluminescence (PL) were carried out to investigate the structural and optical properties of the PS and the ZnO thin films. The ZnO thin films have an extraordinary tendency to grow along the a-axis with a hexagonal wurtzite structure. The growth rate of the ZnO thin films was increased with the increase in the precursor concentration. The crystal quality of the ZnO thin films was improved,and the residual stress was decreased as their thickness increased. Monochromatic indigo and red light emission peaks were observed from the ZnO thin films and the PS, respectively. At an excessively high precursor concentration, a green light emission peak was also observed in the ZnO thin films. The luminescent efficiency of the indigo light emission peak was enhanced with the increase in the precursor concentration.
Effects of Al Concentration on Structural and Optical Properties of Al-doped ZnO Thin Films
Kim, Min-Su,Yim, Kwang-Gug,Son, Jeong-Sik,Leem, Jae-Young Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.4
Aluminium (Al)-doped zinc oxide (AZO) thin films with different Al concentrations were prepared by the solgel spin-coating method. Optical parameters such as the optical band gap, absorption coefficient, refractive index, dispersion parameter, and optical conductivity were studied in order to investigate the effects of the Al concentration on the optical properties of AZO thin films. The dispersion energy, single-oscillator energy, average oscillator wavelength, average oscillator strength, and refractive index at infinite wavelength of the AZO thin films were found to be affected by Al incorporation. The optical conductivity of the AZO thin films also increases with increasing photon energy.
김소아람,남기웅,Kwang Gug Yim,이제원,김양수,임재영 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.3
ZnO nanostructures were grown by the hydrothermal method on ZnO seed layers post-heated in the range 350°C - 500°C. The effects of the post-heated ZnO seed layers on the structural and optical properties of the ZnO nanostructures were investigated by scanning electron microscopy (SEM), x-ray diffraction (XRD)spectroscopy, and photoluminescence (PL) spectroscopy. The average grain sizes in the ZnO seed layers increased with increasing post-heating temperature, and nano-fibrous structures were observed on the surface of the ZnO seed layers post-heated at 450°C. The ZnO seed layers post-heated in the range 350°C - 500°C affected the residual stress, lattice distortion in the ZnO nanostructures and the intensity, positions, and full widths at half maximum of 2θ and PL peaks in the XRD and PL spectra for the ZnO nanostructures.
Kim, Min-Su,Noh, Keun-Tae,Yim, Kwang-Gug,Kim, So-A-Ram,Nam, Gi-Woong,Lee, Dong-Yul,Kim, Jin-Soo,Kim, Jong-Su,Leem, Jae-Young Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.9
The $Mg_xZn_{1-x}O$ thin films with the various content ratio ranging from 0 to 0.4 were prepared by sol-gel spincoating method. To investigate the effects of content ratio on the structural and optical properties of the $Mg_xZn_{1-x}O$ thin films, scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out. With increase in the content ratio, the grain size of the $Mg_xZn_{1-x}O$ thin films was increased, however, at the content ratio above 0.2, MgO particles with cubic structure were formed on the surface of the $Mg_xZn_{1-x}O$ thin films, indicating that the Mg content exceeded its solubility limit in the thin films. The residual stress of the $Mg_xZn_{1-x}O$ thin films is increased with increase in the Mg mole fraction. In the PL investigations, the bandgap and the activation energy of the $Mg_xZn_{1-x}O$ thin films was increased with the Mg mole fraction.
ZnO Nanorods Grown on CdxZn1-xO Seed Layers with Various Cd Mole Fractions
김민수,Do Yeob Kim,Kwang Gug Yim,김소아람,남기웅,Sung-O Kim,Dong-Yul Lee,임재영 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.1
ZnO nanorods were grown on the CdxZn1-xO seed layers with various Cd mole fractions by hydrothermal method. The effects of the Cd mole fraction for CdxZn1-xO seed layers on the structural and optical properties of the ZnO nanorods were investigated by scanning electron microscopy, X-ray diffraction, and photoluminescence. The narrowest full-width at half-maximum and largest grain size of the CdxZn1-xO seed layers, indicating improvement in crystal quality, were observed at the Cd mole fraction of 0.5. At the Cd mole fraction of 0.5, the largest enhancement in the density, the crystal quality, and the growth rate of the ZnO nanorods was observed while their appearance was not affected significantly by the incorporation of the Cd in the CdxZn1-xO seed layers. Consequently, the luminescent properties of the ZnO nanorods were enhanced. The largest improvement in the structural and optical properties of the ZnO nanorods was observed at the Cd mole fraction of 0.5.
ZnO Nanorods Grown on Cd<sub>x</sub>Zn<sub>1-x</sub>O Seed Layers with Various Cd Mole Fractions
Kim, Min-Su,Kim, Do-Yeob,Yim, Kwang-Gug,Kim, Soaram,Nam, Gi-Woong,Kim, Sung-O,Lee, Dong-Yul,Leem, Jae-Young Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.1
ZnO nanorods were grown on the $Cd_xZn_{1-x}O$ seed layers with various Cd mole fractions by hydrothermal method. The effects of the Cd mole fraction for $Cd_xZn_{1-x}O$ seed layers on the structural and optical properties of the ZnO nanorods were investigated by scanning electron microscopy, X-ray diffraction, and photoluminescence. The narrowest full-width at half-maximum and largest grain size of the $Cd_xZn_{1-x}O$ seed layers, indicating improvement in crystal quality, were observed at the Cd mole fraction of 0.5. At the Cd mole fraction of 0.5, the largest enhancement in the density, the crystal quality, and the growth rate of the ZnO nanorods was observed while their appearance was not affected significantly by the incorporation of the Cd in the $Cd_xZn_{1-x}O$ seed layers. Consequently, the luminescent properties of the ZnO nanorods were enhanced. The largest improvement in the structural and optical properties of the ZnO nanorods was observed at the Cd mole fraction of 0.5.