• Journal of the Korean Solar Energy Society
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• v.39 no.1
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• pp.33-40
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• 2019

Al-doped ZnO (AZO) thin films were synthesized on Si(100) wafers via plasma enhanced metal organic chemical vapor deposition (PE-MOCVD) method using diethyl zinc (DEZ) and N-methylpyrrolidine alane (MPA) as precursors. Effects of Al/Zn mixing ratio, plasma power on the surface morphology, crystal structure, and electrical property were investigated with SEM, XRD and 4-point probe measurement respectively. Growth rate of the film decreased slightly with increasing the Al/Zn mixing ratio, however electrical property was enhanced and resistivity of the film decreased greatly about 2 orders from $9.5{\times}10^{-1}$ to $8.0{\times}10^{-3}{\Omega}cm$ when the Al/Zn mixing ratio varied from 0 to 9 mol%. XRD analysis showed that the grain size increased with increasing the Al/Zn mixing ratio. Growth rate and electrical property were enhanced in a mild plasma condition. Resistivity of AZO film decreased down to $7.0{\times}10^{-4}{\Omega}cm$ at an indirect plasma of 100 W condition which was enough value to use for the transparent conducting oxide (TCO) material.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2523-2528
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• 2012

Green phosphors $(Zn_{1-a-b}M_aM^{\prime}_b)_xGa_yS_{x+3y/2}:Eu^{2+}$ (M, M' = alkali earth ions) with x = 2 and y = 2-5 were prepared, starting from ZnO, MgO, $SrCO_3$, $Ga_2O_3$, $Eu_2O_3$, and S with a flux $NH_4F$ using a conventional solidstate reaction. A phosphor with the composition of $(Zn_{0.6}Sr_{0.3}Mg_{0.1})_2Ga_2S_5:Eu^{2+}$ produced the strongest luminescence at a 460-nm excitation. The observed XRD patterns indicated that the optimized phosphor consisted of two components: zinc thiogallate and zinc sulfide. The characteristic green luminescence of the $ZnS:Eu^{2+}$ component on excitation at 460 nm was attributed to the donor-acceptor ($D_{ZnGa_2S_4}-A_{ZnS}$) recombination in the hybrid boundary. The optimized green phosphor converted 17.9% of the absorbed blue light into luminescence. For the fabrication of light-emitting diode (LED), the optimized phosphor was coated with MgO using magnesium nitrate to overcome their weakness against moisture. The MgO-coated green phosphor was fabricated with a blue GaN LED, and the chromaticity index of the phosphor-cast LED (pc-LED) was investigated as a function of the wt % of the optimized phosphor. White LEDs were fabricated by pasting the optimized green (G) and the red (R) phosphors, and the commercial yellow (Y) phosphor on the blue chips. The three-band pc-WLED resulted in improved color rendering index (CRI) and corrected color temperature (CCT), compared with those of the two-band pc-WLED.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.200.2-200.2
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• 2013

Yttrium (Y)이 도핑 된 ZnO 나노 구조물을 수열합성법으로 제작하였다. 먼저 졸겔법으로 SiO2/Si 기판 위에 seed layer (Y-doped ZnO ; Y0.02Zn0.98O)를 제작하였으며 5번의 코팅을 진행하여 박막의 두께는 약 180 nm로 측정이 되었다. 그 후 진공 분위기에서 RTA를 이용하여 $500^{\circ}C$에서 3분간 열처리가 진행되었다. 이어서 수열합성법으로 mole 농도를 0.5~1.0 M 범위에서 변화시키며 YZO 시료를 제작하였다. X-ray diffraction (XRD)을 통해서 Y2O3 또는 결함과 관련된 피크는 관찰이 되지 않았으며, 모든 구조물에서 압축응력이 존재하는 알 수 있었으며, field emission scanning electron microscope (FESEM)에서 나노 구조물의 크기와 형태는 수열합성법의 mole 농도에 많은 영향을 받는 것으로 나타났다. Hall effect 측정을 통해서 모든 구조물은 n-type 전도 특성을 가지는 것으로 나타났다. 또한 광학적 특성인 photoluminescence (PL)에서는 수열합성법의 화학식을 고려할 때 Zn가 rich한 상태에서는 Zn interstitial로 존재하는 것으로 나타났고, mole 농도가 높아 질수록 free exciton에 의한 재결합인 UV emission이 우세하게 나타났다.

• Advances in nano research
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• v.10 no.2
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• pp.191-210
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• 2021

To compare the antifungal effect of two nanomaterials (NMs), nanoparticles of zinc oxide were synthesized by a chemical route and zinc oxide-based nanobiohybrids were obtained using green synthesis in an extract of garlic (Allium sativum). The techniques of X-Ray Diffraction (XRD), Infrared (IR) and Ultraviolet Visible (UV-Vis) absorption spectroscopies and Scanning (SEM) and Transmission Electron Microscopies (TEM) were used to determine the characteristics of the nanomaterials synthesized. The results showed that the samples obtained were of nanometric size (< 100 nm). To compare their antifungal capacity, their effect on Cercospora sp. was evaluated. Test results showed that both nanomaterials had an antifungal capacity. The nanobiohybrids (green route) gave an inhibition of fungal growth of ~72.4% while with the ZnO-NPs (chemical route), inhibition was ~87.1%. Microstructural studies using High Resolution Optical Microscopy (HROM) and ultra-structural analysis using TEM carried out on the treated strains demonstrated the effect of the nanofungicides on the vegetative and reproductive structures, as well as on their cell wall. To account for the antifungal effect presented by ZnO-NPs and ZnO nanobiohybrids on the fungi tested, effects reported in the literature related to the action of nanomaterials on biological entities were considered. Specifically, we discuss the electrical interaction of the ZnO-NPs with the cell membrane and the biomolecules (proteins) present in the fungi, taking into account the n-type nature of the ZnO semiconductor and the electrical behavior of the fungal cell membrane and that of the proteins that make up the protein crown.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.210-214
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• 2016

We investigated the sintering behavior and piezoelectric properties of lead-free $(K_{0.5}Na_{0.5})NbO_3$ ceramics co-doped with excess 0.01 mol ZnO and x mol $MnO_2$, where x was varied from 0 to 0.03. Excess $MnO_2$ addition was found to retard the grain growth and densification during sintering. However, 0.005 mol $MnO_2$ addition improved the piezoelectric properties of 0.01 mol ZnO added $(K_{0.5}Na_{0.5})NbO_3$ ceramics. The planar mode piezoelectric coupling coefficient, electromechanical quality factor, and piezoelectric constant $d_{33}$ of 0.01 mol ZnO and 0.005 mol $MnO_2$ added specimen were 0.40, 304, and 214 pC/N, respectively.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.31-36
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• 2003

In this study, nano-sized NiCuZn-ferrites for the multi-layered chip inductor application were prepared by a coprecipitation method and its electromagnetic properties were analyzed. Also, the property of low temperature sintering were studied with the initial heat treatment of powder.$(Ni_{0.4-x}Cu_xZn_{0.60})_{1+w}(Fe_2O_4)_{1-w}$ (x=0.2, w=0.03) were calcined at $300^{circ}C~750^{circ}C.$ The sintered NiCuZn-ferrites at $900^{\circ}C$ showed good apparent density $4.90g/cm^3,$ and magnetic properties of initial permeability 164 and quality factor 72. As the calcination temperature increase, the grain size of NiCuZn-ferrite increased with irregular grain distribution and its magnetic properties were deteriorated.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.34-37
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• 2007

The crystallographic and magnetic properties of $Fe_{0.9}Zn_{0.1}Cr_2S_4$ have been studied by X-ray diffractometer(XRD), vibrating sample magnetometer(VSM) and $M\"{o}ssbauer$ spectroscopy measurement. The crystal structure was determined by the normal cubic spinel of space group Fd3m and the lattice constant was $a_0=9.9967\;{\AA}$. The specific phenomenon which looks like cusp pattern at 77 K was observed in magnetization corves(ZFC : Zero Field Cooling) under 100 Oe applied field. $N\acute{e}el$ temperature($T_N$) was determined to be 153 K by VSM and $M\"{o}ssbauer$ spectra. The asymmetric 8-line profile has been observed at 4.2 K, which was attributed by the colossal electric quadupole interaction(${\Delta}E_Q$), ${\Delta}E_Q$ has 2.22 mm/s at 4.2 K. The ${\Delta}E_Q$ abruptly decreases around 77 K and then it disappears above 77 K with diminishing of 8-line pattern. The isomer shift $\delta$ at room temperature is 0.48 mm/s relative to Fe metal, which means that the charge state of Fe ions is ferrous in character.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.50-55
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• 2008

AI-doped ZnO(AZO) thin films have been fabricated on glass substrate by sol-gel method, and the effect of Al precursors and post-annealing temperature on the characteristics of AZO thin films was investigated. The sol was prepared with zinc acetate, EtOH, MEA and Al precursors. In order to dope Al in ZnO, two types of aluminum nitrate and aluminum chloride were used as Al precursor. Zinc concentration was 0.5 mol/l and the content of Al precursor was 1 at% of Zn in the sol. The sol was spin-coated on glass substrate, and the coated films were annealed at 550ue for 2 hand were post-annealed at temperature ranges of $300{\sim}500^{\circ}C$ for 2 h in reducing atmosphere ($N_2/H_2$= 9/1). Structural, electrical and optical propertis of the fabricated AZO thin films were analyzed by XRD, FE-SEM, AFM, hall effect measurement system and UV-visible spectroscopy. Optical and electrical properties of AZO thin films prepared with aluminum nitrate as Al precursor were better than those of films prepared with aluminum chloride. The electrical resistivity and the optical transmittance of films decreased with increasing post-annealing temperatures. The minimum electrical resistivity of $2{\times}10^{-3}$ and the maximum optical transmittance of 91% were obtained for the AZO thin films post-annealed at $550^{\circ}C\;and\;300^{\circ}C$, respectively.

• Journal of the Korean Magnetics Society
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• v.10 no.3
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• pp.106-111
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• 2000

The magnetic thin films can be prepared without vacuum process and under the low temperature (<100 $^{\circ}C$) by ferrite plating. We have performed ferrite plating of M $n_{x}$Z $n_{0.22}$F $e_{2.78-x}$ $O_4$(x=0.00~0.08) films and N $i_{x}$Z $n_{0.22}$F $e_{*}$2.78-x/ $O_4$(x=0.00~0.15) films on cover glass at the substrate temperature 90 $^{\circ}C$. The crystal structure of the samples has been identified as a single phase of polycrystal spinel structure by x-ray diffraction technique. The lattice constant in the M $n_{x}$Z $n_{0.22}$F $e_{2.78-x}$ $O_4$films increases but in the N $i_{x}$Z $n_{0.22}$F $e_{*}$2.78-x/ $O_4$films decrease with the composition parameter, x. The saturation magnetization in the M $n_{x}$Z $n_{0.22}$F $e_{2.78-x}$ $O_4$films does not greatly change, in agreement with observations on bulk samples.k samples.k samples.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.31-31
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• 2002

The hydrothermal reaction of Zn(NO₃)₂6H₂O with benzene-1,3-dicarboxylic acid (or isophthalic acid, 1,3-BDCH₂) and pyridine led to the formation of a 1-dimensional coordination polymer with the empirical formula of [Zn₄(1,3-BDC)₃(Py)₂(O/sup 2-/)] (1). On the other hand, the hydrothermal reaction of Tb(NO₃)₃5H₂O with benzene-1,3-dicarboxylic acid (or isophthalic acid, 1,3-BDCH₂) and pyridine gave a 3-D compound [Tb₃(1,3-BDC)₂(H₂O₃] (2). The structures of both compounds have been determined by X-ray diffraction. 1 crystallizes in the monoclinlc space group P2₁/n, a = 10.344(3) Å, b = 18.030(3) Å, c = 18.033(3) Å, = 90.46(2)°, V = 3363.1(13) ,ų, Z = 4. 2 crystallizes in the monoclinic space group C2/n, a = 22.253(5) Å, b = 18.672(4) Å, c = 11.5812 Å, = 101.40(2)°, V = 4717.3(21) ų, Z = 8.