• 한국세라믹학회지
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• 제36권10호
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• pp.1108-1114
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• 1999

Microstructure and electrical properties of ZnO-doped (0-5 mol%) 0.05 Pb(Mn1/3Sb2/3)O3-0.95 PZT ceramics were investigated. Sintering temperature was decreased to 100$0^{\circ}C$ due to eutetic reaction between PbO and ZnO. Grain-size increased up to adding 1mol% ZnO and then decreased. Compositions of grain and grain-boundary were investigated by WDS. Lattice parameter was decreased with ZnO addition. Density increased with ZnO addition and reached to the maximum of 7.84(g/cm2) at 2 mol% ZnO. The effect of ZnO on electrical properties of PMS-PZT was investigated. At 3mol% ZnO addition electromechanical coupling factor(kp) was about 50% and relative dielectric constant($\varepsilon$33/$\varepsilon$0) was 997 Mechanical quality factor(Qm) decreased with ZnO addition. Lattice parameters and tetragonality(c/a) were measured to investigate relationship between the electric properties and substitution of Zn2+. At 3 mol% ZnO tetragonality was maximiged at c/a=1.0035 Curie temperature (Tc) decreased slightly with ZnO addition.

• Environmental Engineering Research
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• 제20권4호
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• pp.329-335
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• 2015

The effects of ion-doping on $TiO_2$ nanotubes were investigated to obtain the optimal catalyst for the effective decomposition of Rhodamine B (RB) through UV photocatalytic oxidation process. Changing the calcination temperature, which changed the weight fractions of the anatase phase, the average crystallite sizes, the BET surface area, and the energy band gap of the catalyst, affected the photocatalytic activity of the catalyst. The ionic radius, valence state, and configuration of the dopant also affected the photocatalytic activity. The photocatalytic activities of the catalysts on RB removal increased when $Ag^+$, $Al^{3+}$ and $Zn^{2+}$ were doped into the $TiO_2$ nanotubes, whereas such activities decreased as a result of $Mn^{2+}$ or $Ni^{2+}$ doping. In the presence of $Zn^{2+}$-doped $TiO_2$ nanotubes calcined at $550^{\circ}C$, the removal efficiency of RB within 50 min was 98.7%.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
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• pp.17-17
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• 2003

Semiconductors with ferromagnetism at room temperature has been actively searched for in recent years; a prospect of devices using both charge and spin continuously gives impetus to the activities. Transition metal doped oxide materials have been of particular interest. Co substituted ZnO [1] and TiO$_2$ [2] thin films, for example, were reported to show ferromagnetic properties at room temperature. However, various studies do not seem to converge on a definite picture [3,4,5]. The issue is rather fundamental: whether a system shows ferromagnetic properties at all, and in case it does, whether the system possesses a close coupling between magnetism and transport properties. In this talk, we shall assess the current status of transition metal doped oxide materials as room temperature ferromagnetic semiconductors.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.410-410
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• 2013

Next-generation nonvolatile memory (NVM) has attracted increasing attention about emerging NVMs such as ferroelectric random access memory, phase-change random access memory, magnetic random access memory and resistance random access memory (RRAM). Previous studies have demonstrated that RRAM is promising because of its excellent properties, including simple structure, high speed and high density integration. Many research groups have reported a lot of metal oxides as resistive materials like TiO2, NiO, SrTiO3 and ZnO [1]. Among them, the ZnO-based film is one of the most promising materials for RRAM because of its good switching characteristics, reliability and high transparency [2]. However, in many studies about ZnO-based RRAMs, there was a problem to get lower current level for reducing the operating power dissipation and improving the device reliability such an endurance and an retention time of memory devices. Thus in this paper, we investigated that highly reproducible bipolar resistive switching characteristics of W doped ZnO RRAM device and it showed low resistive switching current level and large ON/OFF ratio. This may be caused by the interdiffusion of the W atoms in the ZnO film, whch serves as dopants, and leakage current would rise resulting in the lowering of current level [3]. In this work, a ZnO film and W doped ZnO film were fabricated on a Si substrate using RF magnetron sputtering from ZnO and W targets at room temperature with Ar gas ambient, and compared their current levels. Compared with the conventional ZnO-based RRAM, the W doped ZnO ReRAM device shows the reduction of reset current from ~$10^{-6}$ A to ~$10^{-9}$ A and large ON/OFF ratio of ~$10^3$ along with self-rectifying characteristic as shown in Fig. 1. In addition, we observed good endurance of $10^3$ times and retention time of $10^4$ s in the W doped ZnO ReRAM device. With this advantageous characteristics, W doped ZnO thin film device is a promising candidates for CMOS compatible and high-density RRAM devices.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.259-259
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• 2011

염료감응형 태양전지(Dye-Sensitized Solar Cells:DSSC)는 환경 친화적이며, 저가의 공정에 대한 가능성으로 기존의 고가의 결정질 실리콘 태양전지의 경제적인 대안으로 각광을 받고 있다. 최근 염료감응형 태양전지는 투명 전도성 산화막(Transparent Conducting Oxide : TCO)으로 사용되는 Fluorine Tin Oxide (FTO)가 증착된 유리기판 위에 주로 제작된다. FTO는 낮은 비저항과 가시광선 영역에서 높은 투과도를 가지는 우수한 전기-광학적 특성을 갖지만, 비교적 공정이 까다로운 Chemical Vapor Deposition (CVD)법으로 제조하며, 전체 공정비용의 60%를 차지하는 높은 생산단가로 인해 현재 FTO를 대체할 재료개발 연구가 활발히 진행되고 있다. 그 중 ZnO (Zinc Oxide)는 우수한 전기-광학적 특성과 비교적 저렴한 가격으로 새로운 TCO로써 주목받고 있다. ZnO는 넓은 energy band gap (3.4 [eV])의 육방정계 울자이트(hexagonal wurtzite) 결정 구조를 가지는II-VI족 n형 반도체 물질이며, III족 금속원소인 Al, Ga 및 In 등의 불순물을 첨가하면 TCO로서 우수한 전기-광학적 특성과 안정성을 나타낸다. 이들 물질중 $Zn^{2+}$ (0.060 nm)의 이온반경과 유사한 $Ga^{2+}$0.062 nm) 이온이 ZnO의 격자반경을 최소화 시킬 수 있다는 장점으로 최근 주목 받고 있다. 하지만 Ga-doped ZnO (GZO)의 경우 DSC에 사용되는 루테늄 계열의 산성 염료 하에 장시간 두면 표면이 파괴되는 문제가 발생하며, $TiO_2$ paste를 Printing 후 열처리하는 과정에서도 박막의 파괴가 발생할 수 있다. 이를 방지하기 위해 $TiO_2$ Blocking Layer를 GZO 투명전극 위에 증착하였다. 또한, $TiO_2$ Blocking Layer를 적용한 GZO 박막을 전면전극으로 이용하여 DSC를 제작하여 효율을 확인하였다. 2wt%의 $Ga_2O_3$가 도핑된 ZnO 박막은 20mTorr 400$^{\circ}C$에서 Pulsed Laser Deposition (PLD)에 의해 성장되었고, $TiO_2$박막은 Ti 금속을 타겟으로 이용하여 30mTorr 400$^{\circ}C$에서 증착되었다. Scanning electron microscopy (FE-SEM)을 이용한 박막 분석 결과 $TiO_2$가 증착된 GZO 박막의 경우 표면 파괴가 일어나지 않았다. Solar Simulator을 이용하여 I-V특성 측정결과 상용 FTO를 사용한 DSC 수준의 효율을 나타내었다. 이에 따라 Pulsed Laser Deposition을 이용해 제작된 GZO 기판은 $TiO_2$ Blocking Layer를 이용하여 표면 파괴를 방지할 수 있었으며, 이는 향후 염료감응형 태양전지의 투명전극에 적용 가능 할 것으로 판단된다.

• 전자공학회논문지A
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• 제33A권6호
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• pp.127-135
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• 1996

To increase the sensitivity and the selectivity of the sensors to TMA gas, the composition ratio and the growth conditions of the ZnO films are studied. Annealing of the ZnO films in the various time ranges and temperatures in the oxygen is carried out to enhance the stbility of the electrical resistance. Pt/Ti heater deposited on backside of the substrates in used to control the operating temperature of th esensor. The ZnO thin film sensors doped to 4.0 wt% $Al_{2}$O$_{3}$ 1.0wt.% TiO$_{2}$ and 0.2wt.% V$_{2}$O$_{5}$ exhibited a high sensitivity and an excellent selectivity for TMA gas. The sensors made with the thin films annealed at 700$^{\circ}$C for 60 minutes in the oxygen atmosphere had a good stability and linearity. The heater deposited in the ratio of 1 to 1 (Pt:Ti) had a good heating properties. The sensors fabricated using above conditions showed a good response to the actual gases of a mackerel at a step of deterioration after death.

• Applied Science and Convergence Technology
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• 제25권6호
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• pp.162-165
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• 2016

APhotocatalysis process uses ambient oxygen from air and irradiation, fundamentally UV light, to generate oxidation and reduction which can degrade almost all harmful organic and inorganic compounds to nontoxic substances. This study was focused on enhancement of photocatalytic activity which improves the photocatlytic efficiency with $TiO_2$ particle by mixing of certain amounts of Zn particles. We analyzed degradation of organic pollutant materials such as toluene and phenol with the mixed photocatalysis by using UV-visible spectrophotometer and obtained a result that photocatalytic activity is increased with increasing amount of Zn particle. Especially, in the case of $TiO_2$ (1 mmol) and Zn (0.1 mmol) mixture photocatalyst, we obtained at least 2 times higher photocatalytic activity compared with the commercially available $TiO_2$ photocatalyst (Degussa P-25), indicating that our mixed photocatalyts (Zn-doped $TiO_2$) is very effective of removing both organic dye and pollutants and the conversion rate of toluene is much faster than that of phenol.

• The Journal of Advanced Prosthodontics
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• 제9권6호
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• pp.482-485
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• 2017

PURPOSE. This laboratory study aimed to investigate the effect of doping an acrylic denture base resin material with nanoparticles of ZnO, CaO, and $TiO_2$ on biofilm formation. MATERIALS AND METHODS. Standardized specimens of a commercially available cold-curing acrylic denture base resin material were doped with 0.1, 0.2, 0.4, or 0.8 wt% commercially available ZnO, CaO, and $TiO_2$ nanopowder. Energy dispersive X-ray spectroscopy (EDX) was used to identify the availability of the nanoparticles on the surface of the modified specimens. Surface roughness was determined by employing a profilometric approach; biofilm formation was simulated using a monospecies Candida albicans biofilm model and a multispecies biofilm model including C. albicans, Actinomyces naeslundii, and Streptococcus gordonii. Relative viable biomass was determined after 20 hours and 44 hours using a MTT-based approach. RESULTS. No statistically significant disparities were identified among the various materials regarding surface roughness and relative viable biomass. CONCLUSION. The results indicate that doping denture base resin materials with commercially available ZnO, CaO, or $TiO_2$ nanopowders do not inhibit biofilm formation on their surface. Further studies might address the impact of varying particle sizes as well as increasing the fraction of nanoparticles mixed into the acrylic resin matrix.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.99-102
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• 1997

An electronic nose system is an instrument designed far mimicking human olfactory system. It consists generally of gas (odor) sensor array corresponding to olfactory receptors of human nose and artificial neural network pattern recognition technique based on human biological odor sensing mechanism. Considerable attempts to develop the electronic nose system have been made far applications in the fields of floods, drinks, cosmetics, environment monitoring, etc. A portable electronic nose system has been fabricated by using oxide semiconductor gas sensor array and pattern recognition technique such as principal component analysis (PCA) and back propagation artificial neural network The sensor array consists of six thick film gas sensors whose sensing layers are Pd-doped WO$_3$ Pt-doped SnO$_2$ TiO$_2$-Sb$_2$O$_3$-Pd-doped SnO$_2$ TiO$_2$-Sb$_2$O$_{5}$-Pd-doped SnO$_2$+Pd filter layer, A1$_2$O$_3$-doped ZnO and PdCl$_2$-doped SnO$_2$. As an application the system has been used to identify CO/HC car exhausting gases and the identification has been successfully demonstrated.d.

• 한국자기학회지
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• 제15권1호
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• pp.1-6
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• 2005

높은 큐리온도를 가질 수 것으로 예측된 전이금속이 도핑된 ZnO의 전자구조와 자성을 제일원리계산방법을 이용하여 연구하였다. 본 연구에서 전이금속은 Ti, Cr, Mn, Fe, Co, Ni, Ru, Pd, Ag 이고 도핑 수준은 25%로 두고 계산하였다. 자성연구에서 가장 적합한 방법으로 알려져 있는 Full-potential Linearized Augmented Plane Wave(FLAPW)방법을 사용하였으며 교환-상관 전위는 general gradient approximation(GGA)를 사용하였다. 도핑된 전이금속 (Ti, Cr, Mn, Fe, Co, Ni, Ru, Pd, Ag)은 각각 0.83, 3.03, 4.03, 3.48, 2.47, 1.56, 0.43, 0.75, 0.01 ${\mu}_B$의 자기모멘트를 가지며, 전이금속에 이웃한 O 원자도 가안 띠혼성으로 측정 가능한 자기모멘트를 가질 수도 있는 것으로 계산되었다. 3d 전이금속이 도핑된 ZnO는 (CoZnO를 제외하고) 절반금속 특성을 가지는 것으로 계산되었다. 또한 4d 전이금속이 도핑된 경우는 강자성 상태가 상자성 상태에 비해 에너지차이가 크지 않을 뿐 아니라 페르미 준위에 다수 스핀과 소수 스핀 상태 모두가 페르미 준위에 위치해 있어 스핀분극 정도가 낮았다.