• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.481-481
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• 2011

이 논문은 세라믹 노즐(내경: 20 um)을 제작하여 새로운 프린팅 방식인 정전기수력학방식을 이용하여 유리기판위에 직경 30 um의 ZnO seed dot를 패턴하였다. 정전기수력학은 기존의 프린팅 방식과 달리 전기장으로 유도된 노즐을 이용하여 액적을 토출시키는 새로운 프린팅 방법이다. 패턴된 ZnO seed는 열처리후 수열합성법을 이용하여 성장시켰다. 같은 방법으로 잉크젯 프린팅을 이용하여 ZnO seed 패턴 후 열처리하여 수열합성을 이용하여 성장시켰다. 잉크젯 프린팅 방식을 이용하여 성장된 ZnO nanowire는 위성 액적이 떨어져 ZnO seed dot 주변에 ZnO nanowire가 성장하였다. 반면, 정전기수력학 프린팅 방식을 이용하여 성장된 ZnO nanowires는 ZnO seed 패턴 중앙에 집중되어 ZnO nanowire가 성장하였다.

• Journal of the Korean Vacuum Society
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• v.17 no.1
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• pp.40-45
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• 2008

We present the effect of Ga-doping on the electrical, structural and optical properties of ZnO layers with a thickness of ${\sim}500nm$ deposited on glass substrates. Polycrystalline ZnO and Ga-doped ZnO (GZO) layers were deposited by radio frequency (rf) magnetron sputtering at room temperature. Based on the X-ray diffraction (XRD) and transmission electron microscopy (TEM) data, the crystalline quality of Ga-doped ZnO film was improved and GZO film has a preferred orientation along with the (002) crystal direction. The transmittance of the GZO film was enhanced by 10% in the visible region from that of the ZnO film. From photoluminescence (PL) data, the ratio of intensity of near band edge (NBE) emission to deep level (DL) emission was as high as 2.65:1 and 1.27:1 in the GZO and ZnO films, respectively. The res istivities of GZO and ZnO films were measured to be 1.27 and 1.61 $\Omega{\cdot}cm$, respectively. The carrier concentrations of ZnO and GZO film were approximately 1018 and 1020 $cm^2$/Vs, respectively. Based on our experimental results, the Ga-doping improves the electrical, structural and optical properties of ZnO film with potential application.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.3
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• pp.97-101
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• 2005

ZnO thin films were grown at different plume-substrate (P-S) angles of 90$^{\circ}$ (on-axis PLD), 45$^{\circ}$ and 0$^{\circ}$ (off-axis PLD) using pulsed laser deposition. The x-ray diffraction pattern exhibiting a dominant (002) and a minor (101) peak of ZnO indicates all films were strongly c-axis oriented. By observing of (002) peak, the FWHMs of ZnO (002) peaks decreased and c-axis lattice constant approached the value of bulk ZnO as P-S angle decreased. Whereas the carrier concentration of ZnO thin film deposited at P-S angle of 90$^{\circ}$ was ~ 10$^{19}$ /cm$^{3}$, the Hall measurement of ZnO thin films deposited at P-S angles of 0$^{\circ}$ and 45$^{\circ}$ was impossible due to the decrease of the carrier concentration by the improvement of stoichiometry and crystalline quality. By decreasing P-S angle, the grain size of the films and the UV intensity investigated by photoluminescence (PL) increased and UV peak position showed red shift. The improvement of properties in ZnO thin films deposited by off-axis technique was due to the decrease of repulsive force between a substrate and the particle in plume and the relaxation of supersaturation.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.450-450
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• 2011

This study reports the hydrogen sulfide gas sensing properties of ZnO nanorods bundle and the investigation of gas sensing mechanism. Also the improvement of sensing properties was also studied through the application of ZnO heterstructured nanorods. The 1-Dimensional ZnO nano-structure was synthesized by hydrothermal method and ZnO nano-heterostructures were prepared by sonochemical reaction. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) spectra confirmed a well-crystalline ZnO of hexagonal structure. The gas response of ZnO nanorods bundle sensor increased with increasing temperature, which is thought to be due to chemical reaction of nanorods with gas molecules. Through analysis of X-ray photoelectron spectroscopy (XPS), the sensing mechanism of ZnO nanorods bundle sensor was explained by well-known surface reaction between ZnO surface atoms and hydrogen sulfide. However at high sensing temperature, chemical conversion of ZnO nanorods becomes a dominant sensing mechanism in current system. In order to improve the gas sensing properties, simple type of gas sensor was fabricated with ZnO nano-heterostructures, which were prepared by deposition of CuO, Au on the ZnO nanorods bundle. These heteronanostructures show higher gas response and higher current level than ZnO nanorods bundle. The gas sensing mechanism of the heteronanostructure can be explained by the chemical conversion of sensing material through the reaction with target gas.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.2
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• pp.70-76
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• 2014

$Zn_2TiO_4$, using an anatase form of $TiO_2$ on zinc crystalline glaze, was shown as effective nuclear agent. Thus the effects on glaze were studied with synthesized $Zn_2TiO_4$ at low temperature. First, the chromophore elements were employed in synthesized $Zn_2TiO_4$ then add them in the zinc crystalline glaze. Crystal creation and development of color by $Zn_2TiO_4$ addition on the zinc crystalline glaze were more effective. Addition of $Zn_2TiO_4$, which is developed in low range temperature, is effected as zinc crystalline nuclear in the willemite glaze. When 5 wt% of synthesized $Zn_2TiO_4$ was added to the willemite glaze, nuclear creation increases and steadily retains. Therefore addition of respectively doped $Zn_2TiO_4$ with CoO, NiO, and CuO would increase doped effects in the glaze, various color willemite crystal were obtained.

• Korean Journal of Metals and Materials
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• v.56 no.12
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• pp.900-909
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• 2018

A $ZnO/TiO_2$ photocatalyst decorated with PbS quantum dots (QDs) was synthesized to achieve high photocatalytic efficiency for the decomposition of dye in aqueous media. A $TiO_2$ porous layer, as a precursor photocatalyst, was fabricated using micro-arc oxidation, and exhibited irregular porous cells with anatase and rutile crystalline structures. Then, a ZnO-deposited $TiO_2$ catalyst was fabricated using a zinc acetate solution, and PbS QDs were uniformly deposited on the surface of the $ZnO/TiO_2$ photocatalyst using the successive ionic layer adsorption and reaction (SILAR) technique. For the PbS $QDs/ZnO/TiO_2$ photocatalyst, ZnO and PbS nanoparticles are uniformly precipitated on the $TiO_2$ surface. However, the diameters of the PbS particles were very fine, and their shape and distribution were relatively more homogeneous compared to the ZnO particles on the $TiO_2$ surface. The PbS QDs on the $TiO_2$ surface can induce changes in band gap energy due to the quantum confinement effect. The effective band gap of the PbS QDs was calculated to be 1.43 eV. To evaluate their photocatalytic properties, Aniline blue decomposition tests were performed. The presence of ZnO and PbS nanoparticles on the $TiO_2$ catalysts enhanced photoactivity by improving the absorption of visible light. The PbS $QDs/ZnO/TiO_2$ heterojunction photocatalyst showed a higher Aniline blue decomposition rate and photocatalytic activity, due to the quantum size effect of the PbS nanoparticles, and the more efficient transport of charge carriers.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1471-1474
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• 1998

ZnO Varistor with composition of ZnO, $Bi_2O_3$, $Sb_2O_3$, CoO, NiO, $MnO_2$, $Cr_2O_3$, $Al_2O_3$ was fabricated by sintering methods. The purpose of this paper is to present certified voltage-current test data and a summary of electrical characteristics of the ZnO varistors.

• Korean Journal of Materials Research
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• v.21 no.4
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• pp.232-235
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• 2011

ZnO nanorods for gas sensors were prepared by a hydrothermal method. The ZnO gas sensors were fabricated on alumina substrates by a screen printing method. The gas-sensing properties of the ZnO nanorods were investigated for $CH_4$ gas. The effects of growth time on the structural and morphological properties of the ZnO nanorods were investigated by X-ray diffraction and scanning electron microscope. The XRD patterns of the nanocrystallized ZnO nanorods showed a wurtzite structure with the (002) predominant orientation. The diameter and length of the ZnO nanorods increased in proportion to the growth time. The sensitivity of the ZnO sensors to 5 ppm $CH_4$ gas was investigated for various growth times. The ZnO sensors exhibited good sensitivity and rapid response-recovery characteristics to $CH_4$ gas, and both traits were dependent on the growth time. The highest sensitivity of the ZnO sensors to $CH_4$ gas was observed with the growth time of 7 h. The response and recovery times were 13 s and 6 s, respectively.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.2
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• pp.33-41
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• 2005

ZnO epilayer was synthesized by the pulsed laser deposition(PLD) process on Al$_2$O$_3$ subsorte after irradiating the surface of ZnO sintered pellet by ArF(193nm) excimer laser. The epilayers of ZnO were achieved on sapphire(A1203) substrate at the 境mperature of 400$^{circ}$C. The crystalline structure of epilayer was investigated by the Photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of ZnO epilayer measure with Hall effect by van der Pauw mothod are $8.27\times$1016cm$^{-3}$ and 299 cm$^{2}$/V$\cdot$s at 293 K respectively, The temperature dependence of the energy band gap of the ZnO obtained from the absorption spectra was well described by the Varshni's relation, E$_g$(T)= 3.3973 eV - ($2.69\times$ 10$^{-4}$ eV/K)T$^{2}$/(T + 463K). After the as-grown ZnO epilayer was annealed in Zn atmospheres, oxygen and vaccum the origin of point defects of ZnO atmospheres has been investigated by the photoluminescence(PL) at 10K. The native defects of V$_{Zn}$, V$_{O}$, Zn$_{int}$, and O$_{int}$ obtained by PL measurements were classified as a donor or acceptor type. In addition we concluded that the heat-treatment in the oxygen atmosphere converted ZnO thin films to an optical p-type. Also, we confirmed that vacuum in ZnO/Al$_2$O$_3$ did not firm the native defects because vacuum in ZnO thin films existed in the form of stable bonds.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.424-424
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• 2012

ZnO는 수열합성법을 통해 저온에서 단결정으로 성장할 수 있기 때문에 광전소자 및 압전소자로 응용되고 있으나, 성장된 ZnO nanowire 내부 산소 결함 및 표면에 OH기의 흡착에 의해 소자특성 저하를 발생시킨다. 본 연구에서는 ZnO의 결함의 최소화를 위해 Glass 기판에 수열합성법으로 성장된 ZnO nanowire를 ICP 플라즈마 장치를 이용하여 O2 25 sccm, Base Pressure $1.5{{\times}}10^{-3}$ Torr을 기준으로 파워와 시간에 따라 표면처리 하였다. 플라즈마 처리된 ZnO nanowire의 결함특성과 형상을 XPS와 FE-SEM를 통하여 분석하였으며, ZnO nanowire의 소자특성을 평가를 위해 Kapton Film/AZO/ZnO nanowire/PMMA/Au 구조의 발전기를 제작하였다. 150 W, 10 min에서 532.4 eV의 -OH결합이 최소화됨을 확인하였으며, 이를 이용하여 Flexible ZnO nanowire 발전기 제작 했을 경우 최대 Voltage 5 V, Current 156 nA 전기적 특성을 확인하였다.