• Journal of the Korean Electrochemical Society
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• v.22 no.1
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• pp.13-21
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• 2019

Prussian blue analogues(PBAs) are comprised of cyano-bridged transition metal ions. The wide and unique open-framework structures of the PBAs enable reversible intercalation and deintercalation of various ions such as $Na^+$, $K^+$, $Mg^{2+}$, $Zn^{2+}$, etc. In addition, since PBAs are synthesized through coprecipitation reaction in aqueous solution at room temperature, they are produced economically and environmentally friendly. However, the formation of crystals proceeds rapidly, and defects such as vacancy and crystal water tend to be present in the crystals, thereby affecting key battery performance. Therefore, significant efforts to inhibit defects in PBAs have been made. In the case of vacancy, the reaction rate was controlled at the synthesis stage to reduce the formation of vacancy, and the crystal water was removed by heat treatment under vacuum. In addition, by adding transition metals that do not react within the structure of PBA, the structural instability during the electrochemical reaction was largely alleviated.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.424-424
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• 2012

나노 구조의 반도성 산화물은 독특한 구조적 특성으로 전기적, 광학적 특성을 향상 시킬 수 있다. 현재 연구되고 있는 나노 구조의 반도성 산화물 중 Zinc oxide (ZnO)는 3.37 eV의 bandgap를 갖는 wurtzite 구조체로서 상온에서 60 meV의 exciton binding energy 등 우수한 특성으로 인하여 최근 많이 연구되고 있다. 특히 단파장 light emitting diode 재료로써 기대를 모으고 있는데, 이를 실현하기 위한 가장 큰 문제점이 바로 안정적인 p-type ZnO 박막의 제조이다. 지금까지 알려진 바에 따르면 P를 doping한 후 급속 열처리한 경우 p-type의 전기전도도를 갖는 ZnO 박막을 제조할 수 있다고 보고되어 있으나 vacancy 농도에 따른 불안정적인 요소가 해결해야 할 문제로 남아 있다. 최근 Ag를 doping 시킨 ZnO 박막의 p-type 반도체로서 가능성에 대한 보고가 제기되고 있다. 합성 방법과 조건에 따라서 수 nm에서 수십 또는 수백 nm 크기의 구형 입자나, 리본, 와이어, 로드 그리고 꽃모영 등 다양한 형상을 갖는 나노 구조체를 합성 할 수 있다. 본 연구에서는 ZnO:Ag 박막을 radio-frequency sputtering 방법으로 증착하여 그 물성을 분석하였다. 보통의 sputtering 증착법에서 사용되는 sintering된 타겟과 달리 본 실험은 분말 타겟을 이용하여 박막을 증착하였다. 타겟은 95 wt% ZnO와 5 wt% Ag를 서로 혼합하여 제조하였다. 본 발표에서는 박막의 증착압력 및 증착 온도의 변화에 따른 ZnO:Ag 박막의 구조적, 광학적 특성에 대하여 논의 할 것이다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.33-34
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• 2005

Electrodes were fabricated on a single ZnO nanowire by photolithography process, metal evaporation, and lift-off. The slow photoresponses of the ZnO nanowire under the continuous illumination of 325nm-wavelength light (corresponding to above-bandgap excitation) indicate that the traps related to oxygen vacancy disturb the flow of electron in ZnO nanowire. The photoresponse and PL spectra were measured, and observed that the excitonic band in the PL spectrum was absent in the photoresponse.

• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.90-94
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• 1998

Self diffusion coefficients of $^{67}$Co and impurity diffusion coefficients of $^{51}$Mn and $^{65}$Zn in single crystalline CoO have been measured by applying different radioactive isotopes simultaneously. To compare the residual activity method and the tracer sectioning method we analyzed our tracer diffusion experiments by using both methods simultaneously. According to our experimental results, the diffusion coefficients obtained from both methods are identical within experimental error, demonstrating the relibility of our experimental procedures. The diffusion coefficients of all the isotopes obtained during these test experiments for the methodology are similar in magnitude and show similar dependences on oxygen partial pressure. These first observations indicate that impurity diffusion of Mn and Zn occur via a vacancy mechanism as known for self diffusion of cobalt.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.6
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• pp.111-117
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• 2002

The high quality and a nearly stoichometric growth of $Cd_{1-y} Zn_y$/Te(y＝0.04) epilayers have been successfully grown on GaAs substrate by hot wall epitaxy (HWE) by optimizing the growth condition including the preheating treatment and Cd reservoir temperature. The relationship between quality and thickness was examined and best value of FWHM from X-ray rocking curve of 121 arcsec are obtained. Also, emission peaks related to the recombination of free excitons such as the ground state and the first excited state were observed in the PL spectrum at 4.2K. The ($A^0$, X) emission related to Cd vacancy and deep level emission was not measured. These results indicated that the grown CZT/GaAs epilayer was high qualify and purity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.9
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• pp.697-700
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• 2011

Thin-film transistors(TFTs) with magnesium zinc tin oxide(MZTO) channel layer are fabricated by solution-process. The threshold voltage (Vth) shifted toward positive directly with increasing Mg contents in MZTO system. Because the Mg has a lower standard electrode potential (SEP) than Sn, Zn, thus degenerate the oxygen vacancy ($V_O$). As a result, the Mg act as carrier suppressor and oxygen binder in the MZTO as well as a Vth controller.

• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.199-205
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• 2010

The electrical properties and defect states in ZnO substrates were studied during high-energy electron beam irradiations. 1 MeV and 2 MeV electron-beam with dose of $1{\times}10^{16}$ electrons/$cm^2$ were irradiated on Zn-surface of the sample. In the sample irradiated by 1 MeV, the leakage current was increased by electron-beam induced surface defects, while the enhancement of on/off property and the decrease of leakage current appeared in the 2 MeV irradiated sample. From the deep level transient spectroscopy measurements for these samples, it showed that the defect states with the activation energies of $E_c$-0.33 eV and $E_v$+0.8 eV are generated during the high energy electron-beam irradiation. Especially, it considered that the $E_c$-0.33 eV state related with O-vacancy affects to their electrical properties.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.242-242
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• 2012

Transparent oxide semiconductors are increasingly becoming one of good candidates for high efficient channel materials of thin film transistors (TFTs) in large-area display industries. Compare to the conventional hydrogenated amorphous silicon channel layers, solution processed ZnO-TFTs can be simply fabricated at low temperature by just using a spin coating method without vacuum deposition, thus providing low manufacturing cost. Furthermore, solution based oxide TFT exhibits excellent transparency and enables to apply flexible devices. For this reason, this process has been attracting much attention as one fabrication method for oxide channel layer in thin-film transistors (TFTs). But, poor electrical characteristic of these solution based oxide materials still remains one of issuable problems due to oxygen vacancy formed by breaking weak chemical bonds during fabrication. These electrical properties are expected due to the generation of a large number of conducting carriers, resulting in huge electron scattering effect. Therefore, we study a novel technique to effectively improve the electron mobility by applying environmental annealing treatments with various gases to the solution based Li-doped ZnO TFTs. This technique was systematically designed to vary a different lithium ratio in order to confirm the electrical tendency of Li-doped ZnO TFTs. The observations of Scanning Electron Microscopy, Atomic Force Microscopy, and X-ray Photoelectron Spectroscopy were performed to investigate structural properties and elemental composition of our samples. In addition, I-V characteristics were carried out by using Keithley 4,200-Semiconductor Characterization System (4,200-SCS) with 4-probe system.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1270-1271
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• 2008

Effects of thin ZnO/Mg interlayers on electrical and optical properties between p-GaN and ITO were characterized for its application to GaN-LEDs. The ZnO and Mg layers were deposited to have various thicknesses (1${\sim}$6nm for ZnO and 1${\sim}$2nm for Mg) by sputtering. After RTA process, the atomic migration between Mg and ZnO and the formation of Ga vacancy were observed from SIMS depth profile, resulting in the increase of hole concentration and the reduction of band bending at the surface region of p-GaN. The sample using ZnO(2nm)/Mg(2nm) interlayer produced the lowest contact resistance with SBH(Schottky barrier height) of 0.576 eV and the transmittance higher than 83% at a wavelength of 460nm when annealed at 500$^{\circ}C$ for 3min in air ambient.

• Advances in Energy Research
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• v.3 no.2
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• pp.117-124
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• 2015

In this paper, we have reported an enhancement in thermoelectric properties of un-doped zinc oxide (ZnO) grown by molecular beam epitaxy (MBE) on silicon (001) substrate by annealing treatment. The grown ZnO thin films were annealed in oxygen environment at $500^{\circ}C-800^{\circ}C$, keeping a step of $100^{\circ}C$ for one hour. Room temperature Seekbeck measurements showed that Seebeck coefficient and power factor increased from 222 to $510{\mu}V/K$ and $8.8{\times}10^{-6}$ to $2.6{\times}10^{-4}Wm^{-1}K^{-2}$ as annealing temperature increased from 500 to $800^{\circ}C$ respectively. This observation was related with the improvement of crystal structure of grown films with annealing temperature. X-ray diffraction (XRD) results demonstrated that full width half maximum (FWHM) of ZnO (002) plane decreased and crystalline size increased as the annealing temperature increased. Photoluminescence study revealed that the intensity of band edge emission increased and defect emission decreased as annealing temperature increased because the density of oxygen vacancy related donor defects decreased with annealing temperature. This argument was further justified by the Hall measurements which showed a decreasing trend of carrier concentration with annealing temperature.