• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1159-1161
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• 1993

This paper may be presented the carrier oscillation properties for the varistor fabricated by a new method of three-composition seed grain, in order to analyze the behavior of carriers at the its equivalent circuit model. The oscillation phenomena of carriers appeared from current-voltage characteristics under knee voltage is shown by the transient flow of non trapped carriers group in the trap level of intergranular layer, surface state and/or depletion layer. However, Current oscillation phenomena is hardly shown in the high electric field. The injected carriers from both electrodes are directly flowed from the conduction band of forward biased grain through the intergranular layer into the reverse biased grain, because the trap level in the electric field above the knee voltage is mostly filled.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.988-993
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• 2004

Luminescence characteristics of Ag-doped ZnO as the quantum dot materials to increasing the efficiency on dye-sensitized solar cells (DSC) have been studied. Ag doped ZnO powder was produced by the self-sustaining combustion process using ultrasonic spraying heating method. Luminescence wavelength region of the ZnO by Ag doping was shifted to longer wavelength. Tn the case of the Ag doped ZnO powder, broad luminescence spectrum centered on 600nm was observed. On the other hand, we compared PL data of RTA treated ZnO:Ag film at various temperatures because the front electrode of solar cell was in need of the sintering process. In XRD and PL data for RTA treated film at the 500$^{\circ}C$ showed good property. And, it was found that the grain size wasn't growing but only optical property was changed. According to the result of XRD, PL, absorption, emission spectrum and DV-X${\alpha}$ used in theoretical calculation, it is considered to be possible to use Ag doped ZnO as quantum dot material for improving DSC efficiency.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.141-145
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• 2011

ZnO:Al thin films were deposited by RF magnetron sputtering with various base pressure, and their structural, optical, and electrical properties were studied. The influence of the base pressure on the ZnO:Al thin film was confirmed and a high-quality thin film was obtained by controlling the base pressure. In all Al-doped ZnO thin films, the preferred orientation of (002) plane was observed and light transmittance in visible region (400 nm~800 nm) had above 85%. With decreasing of base pressure, crystallinity, resistivity, and figure of merit were improved. The improvement of resistivity with base pressure was attributed to the change of grain size.

• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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• pp.965-968
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• 2007

In this study we investigated the variation of the substrate temperatures using RF sputtering to identify the effect on the structure and electrical properties by c-axis orientation of ZnO thin film. ZnO thin films were prepared on Al/Si substrate. In our experimental results, ZnO thin film at $300^{\circ}C$ was well grown with (002) peak of ZnO thin film, the thin film showed the high resistivity with the value of $5.9{\times}10^7\;{\Omega}cm$ and the roughness with 27.06 nm. As increased the substrate temperatures, the grain size of ZnO thin films was increased. From these results, we could confirm the suitable substrate temperature of ZnO thin films for FBAR(film bulk acoustic resonator).

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.316-320
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• 1991

The dielectric properties of the ZnO varistor fabricated by the method of 3-composition seed grain was studied. In this paper, we present the C-V charateristic for the specimen. The dielectric constant and disppation which changed with additives may be explained on the basis of the deplation layer; the presence of deplation layer has been inferred by donor and state density obtained from the $1/C^2$ vs. V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1991.10a
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• pp.40-43
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• 1991

The low-voltage ZnO varistor fabricated by a new method with three-composition seed grain are studied. The knee voltage about 5V$\_$0.5[A/$\textrm{cm}^2$]/ for sample #7 among the various samples are observed, and activation energy in the obmic region and trap level in the double sohottky region for each samples are 0.359∼0.450eV and 0.553∼0.620eV, respectively. It is concluded that the change of knee voltage may be caused by trap level in double sohottky region rather than activation energy in the ohmic region.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1495-1497
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• 1998

The effects of lanthania on the microstructure and electrical characteristics of Pr-based ZnO varistors were investigated. The average grain size was increased in the range of 21.9$\sim$56.3${\mu}m$ with increasing lanthania content(0.0$\sim$2.0mol%). La was largely segregated at the grain boundary. As lanthania content increases, threshold voltage and nonlinear coefficient were decreased and leakage current was increased. In particular 2.0mol% lanthania-added varistor exhibited low threshold, voltage 17.0V/mm and nonlinear coefficient of around 6. Based on these results, this varistor can be said to be used as low-voltage varistor, if nonlinear coefficient is somewhat improved forward.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1211-1213
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• 2004

In this paper, in other the study shift a degradation and electrical properties on ZnO based grain beurdry layer, we mearured thermally stmulated current. Also the TSC was investigated for understanding of GBL's interfacial carrier shift on bias voltage, bias time, bias temperature. as a result, the two peahs of $p_1$, $p_2$ was observed by conduction of the trapped carrier of border between the oxidation layer and the grains $P_3$ and $P_4$ Peaks observed to the ionization excition excitation in the grain.

• Korean Journal of Crystallography
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• v.10 no.2
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• pp.136-144
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• 1999

고주파 마그네트론 스퍼터법을 이용한 Al:ZnO(AZO) 박막 증착시, 증착 조건에 따른 미세구조 변화를 조사하였으며, 이를 전기적 광학적 성질과 상관하여 고찰하였다. 박막은 기판 온도가 증가함에 따라 c축이 기판표면에 수직으로 놓이는 주상구조로 성장하였으며, 스퍼터 파워가 증가함에 따라 증착 속도와 입자의 크기가 증가한 반면 결정성은 저하되었다. 증착된 박막은 가시광선영역에서 85% 이상의 광 투과도를 나타내었으며 Al 첨가에 의해 광학적 밴드갭이 약 0.15 eV 증가하였다. 주상구조로 성장한 입자들은 저각 입계(low angle grain boundary)와 특수 입계(special grain boundary)를 형성하였으며, 특히 Σ=7 [001] (210)A/(110)B 입계의 규칙적인 원자배열 및 원자이완을 HRTEM을 이용하여 고찰하였다.