• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.55 no.5
• /
• pp.257-262
• /
• 2006

To evaluate the change in protective levels of zinc oxide (ZnO) varistors after the surge absorption, this paper investigated the effects of the number of injection and amplitude of lightning surges on the life of ZnO varistors for low voltages. Leakage currents flowing through ZnO varistors subjected to the $8/20{\mu}s$ impulse currents under 60 Hz AC voltages were measured. The surge simulator system ECAT that can generate $8/20{\mu}s$ impulse currents with a peak short-circuit of 5 $[kA_p]$ was used. The ZnO varistor leakage current increases with exposure to impulse current, and the number of injection of $8/20{\mu}s$ impulse currents to breakdown was inversely proportional to the amplitude of the test current. Behaviors of ZnO varistor leakage currents were strongly dependent on the number of injection and amplitude of $8/20{\mu}s$ impulse currents. ZnO varistors degrade gradually when subjected to impulse current, and the resistive leakage current flowing through ZnO varistors subjected to the $8/20{\mu}s$ impulse currents under 60 Hz AC voltages was significantly increased after a certain number of injection that is dependent on the amplitude of the test impulse current. As a result, the life of ZnO varistors mainly depends on the amplitude and occurrence frequency of lightning surges.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.164-164
• /
• 2010

The impurity doped ZnO has been extensively studied because of its optoelectric properties. GIZO (Ga-In-Zn-O) amorphous oxide semiconductors has been widely used as transparent flexible semiconductor material. Recently, various amorphous transparent semiconductors such as IZO (In-Zn-O), GIZO, and HIZO (Hf-In-Zn-O) were developed. In this work, we examined the local structures of IZO, GIZO, and HIZO. The local coordination structure was investigated by the extended X-ray absorption fine structure. The IZO, GIZO and HIZO thin films ware deposited on the glass substrate with thickness of 400nm by the radio frequency sputtering method. The targets were prepared by the mixture of $In_2O_3$, ZnO and $HfO_2$ powders. The percent ratio of In:Zn in IZO, Ga:In:Zn in GIZO and Hf:In:Zn in HIZO was 45:55, 33:33:33 and 10:35:55, respectively. In this work, we found that IZO, GIZO and HIZO are all amorphous and have a similar local structure. Also, we obtained the bond distances of $d_{Ga-O}=1.85\;{\AA}$, $d_{Zn-O}=1.98\;{\AA}$, $d_{Hf-O}=2.08\;{\AA}$, $d_{In-O}=2.13\;{\AA}$.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.14 no.2
• /
• pp.33-41
• /
• 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 KIEE Conference
• /
• 2005.07c
• /
• pp.1884-1886
• /
• 2005

KrF 펄스 레이저 증착법(pulsed laser deposition: PLD)으로 ZnO 박막을 증착하여 평판 디스플레이 소자 구동용 박막 트랜지스터(thin film transistor) 소자를 제작하였다. 전도성이 높은 실리콘웨이퍼(c-Si, 하부전극) 기판 위에 LPCVD 법으로 silicon nitride 박막을 절연막으로 형성하고, 다양한 공정 조건에서 펄스 레이저 증착법으로 제작한 ZnO 박막을 증착하여 채널층으로 하였으며, Al 박막을 증착하고 패터닝하여 소스 및 드레인 전극으로 하였다. ZnO 박막의 증착 시에 기판 온도를 다양하게 조절하고 산소 분압을 변화시켜 ZnO 박막의 특성을 조절하였다. 제작된 박막의 표면특성은 AFM(atomic force microscopy)로 분석하고, 결정특성은 XRD(X-ray diffraction)로 조사하였다. ZnO 박막의 전기적 특성은 Hall-van der Pauw 법으로 측정하였고, 광학 투과도(optical transparency)를 UV-visible photometer로 조사하였다. ZnO-TFT 소자는 $10^6$ 수준의 on-off ratio와 $2.4{\sim}6.1cm^2/V{\cdot}s$의 전계효과이동도(field effect mobility)를 보였다.

• Journal of the Korean Ceramic Society
• /
• v.30 no.9
• /
• pp.723-730
• /
• 1993

The mechanism of formation of perovskite phase and the dielectric properties of PZMN[Pb(Zn, Mg)1/3Nb2/3O3] ceramics were examined using two different types of the columbite precursors, (Mg, Zn)Nb2O6 (MZN) and MgNb2O6＋ZnNb2O6 (MN＋ZN). The formatin of perovskite phase in PbO＋MN＋ZN system is characterized by an initial rapid formation of Mg-rich perovskite phase, followed by a sluggish formation of Zn-rich perovskite phase. On the other hand, thepyrochlore/perovskite transformation in the PbO＋MZN system proceeded uniformly with a spatial homogeneity. The degree of diffuseness of the rhombohedral/cubic phase transitionis higher in the PbO＋MN＋ZN system than in the PbO＋MZN specimen, indicating a broadened compositional distributjion of the B-site catons (Nb+5, Zn+2, Mg+2) in the PbO＋MN＋ZN system.

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

• Restorative Dentistry and Endodontics
• /
• v.48 no.1
• /
• pp.3.1-3.14
• /
• 2023

Objectives: This study evaluated the effect of different nanoparticulated zinc oxide (nano-ZnO) and conventional-ZnO ratios on the physicochemical properties of calcium aluminate cement (CAC). Materials and Methods: The conventional-ZnO and nano-ZnO were added to the cement powder in the following proportions: G1 (20% conventional-ZnO), G2 (15% conventional-ZnO + 5% nano-ZnO), G3 (12% conventional-ZnO + 3% nano-ZnO) and G4 (10% conventional-ZnO + 5% nano-ZnO). The radiopacity (R_ad), setting time (S_et), dimensional change (D_c), solubility (S_ol), compressive strength (C_st), and pH were evaluated. The nano-ZnO and CAC containing conventional-ZnO were also assessed using scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Radiopacity data were analyzed by the 1-way analysis of variance (ANOVA) and Bonferroni tests (p < 0.05). The data of the other properties were analyzed by the ANOVA, Tukey, and Fisher tests (p < 0.05). Results: The nano-ZnO and CAC containing conventional-ZnO powders presented particles with few impurities and nanometric and micrometric sizes, respectively. G1 had the highest Rad mean value (p < 0.05). When compared to G1, groups containing nano-ZnO had a significant reduction in the S_et (p < 0.05) and lower values of D_c at 24 hours (p < 0.05). The C_st was higher for G4, with a significant difference for the other groups (p < 0.05). The S_ol did not present significant differences among groups (p > 0.05). Conclusions: The addition of nano-ZnO to CAC improved its dimensional change, setting time, and compressive strength, which may be promising for the clinical performance of this cement.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.298-299
• /
• 2010

Cu(In, Ga)Se2 (CIGS) 박막 태양전지는 Soda lime glass/Mo/CIGS/CdS/ZnO/ITO/Al 의 구조를 가지고 있다. CIGS 화합물은 direct bandgap 구조를 하고 있으며, 광흡수율이 다른 어떤 물질들 보다 뛰어나 박막으로도 충분히 태양광을 흡수할 수 있다. 또한 Ga의 도핑 농도에 따른 밴드갭 조절도 가능하다. 이러한 성질들로 인해 현재 박막태양전지로서 20.1%의 최고효율을 가지고 있다.[1] CIGS 박막 태양전지에서 p-CIGS layer와 스퍼터링으로 증착되는 n-ZnO layer사이의 buffer 층으로 chemical bath deposition (CBD)-CdS 박막을 주로 사용한다. CBD-CdS 박막은 n-ZnO 스퍼터로 증착 시킬 때, CIGS 층의 손상을 최소화하고, 이 두 층 사이에서의 격자상수와 밴드갭의 차이를 줄여주어 CIGS 박막태양전지의 효율을 증가 시키는 역할을 한다. 하지만, Cd (카드뮴)의 심각한 독성과 낮은 밴드갭(2.4eV)으로 인해 CIGS 층에서의 광흡수율을 줄여, CdS를 대체할 새로운 buffer 층의 필요성이 대두되었다.[2] 그 대안으로 ZnS, Zn(O, S, OH), (Zn, Mg)O, In2S3 같은 물질이 연구되고 있다. 현재 CBD-ZnS를 buffer 층으로 사용한 CIGS 박막태양전지의 효율은 최고 18.6%로 CBD-CdS의 최고효율보다는 약 1.5% 낮지만, ZnS가 높은 밴드갭(3.7~3.8eV)과 Cd-free 물질이라는 점에서 CdS를 대체할 물질로 각광받고 있다. 본 연구에서는 기존의 CdS 박막을 제조하는 방법과 같은 방법인 CBD를 이용하여 ZnS 박막을 제조하였다. ZnS 박막을 제조하기 위해서는 Zinc sulfate, Thiourea, 암모니아가 사용된다. 암모니아의 mol 농도에 따른 CBD-ZnS/CIGS 박막태양전지의 효율 변화를 관찰하기 위해 암모니아의 mol 농도는 1 mol, 2 mol, 3 mol, 4 mol, 5 mol, 6 mol, 그 이상의 과량을 사용하여 실험하였다. 실험 결과, 암모니아농도 5 mol에서 효율 13.82%를 확인할 수 있었다. 최고효율을 보인 조건인 암모니아 농도가 5 mol 일 때, Voc는 0.602V, Jsc는 33.109mA/cm2, FF는 69.4%를 나타내었다.

• Clean Technology
• /
• v.16 no.4
• /
• pp.292-296
• /
• 2010

We fabricated quantum dot sensitized solar cells(QDSSC) using PbS as a sensitizer and measured the solar energy conversion efficiency. After growing ZnO nanowires on the substrate by low temperature ammonia solution reaction, PbS QDs were deposited on ZnO nanowires by SILAR(Successive ionic layer adsorption and reaction) method. The morphology and crystallinity of PbS/ZnO nanowires were studied by SEM and XRD. In this study, the maximum conversion efficiency of QDSSC using PbS was 0.075% at one sun, which was lower than that of QDSSC using other sensitizers. The reasons it showed relatively low efficiency are i) the probability of type-I band gap arrangement between ZnO and PbS, ii) disturbance of electron migration by the various-sized PbS band gap, iii) stability dip by the chemical reaction of PbS QDs with electrolyte. To solve these problems, researches about controlling the size distribution of PbS and new type electrolyte would be needed.

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1433-1435
• /
• 1997

ZnO shows the properties of wide conductivity variation, high optical transmittance, and excellent piezoelectricity. Using these properties of ZnO, the material applications were extended to sensors, SAW filters, solar cells, and display devices. This paper investigated transmittance influencing factors for thin film ZnO grown by RF magnetron sputtering. The growth rate and structural investigation were carried out in conjunction with optical transmittance characteristics of thin film ZnO. The glass substrate temperature of $175^{\circ}C$ exhibited a preferential crystallization along (002) orientation. Transmittance of ZnO film deposited at the substrate temperature of $175^{\circ}C$ showed higher than 92%. An active sputter gas was investigated with a variation of $O_2$ partial pressure from 0 to 10% in an Ar atmosphere. ZnO film grown in 100% Ar gas shows that a reduced transmittance of 82% at the short wavelengths and decreased resistivity value. As the partial pressure of $O_2$ gas increased, the optical transmittance was increased above 90% at the short wavelengths, however, resistivity was drastically increased to higher than $10^4{\Omega}$-cm.