• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.3
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• pp.165-169
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• 2015

In this paper, in order to develop the composition ceramics with the excellent dielectric properties, $Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3$ ceramics were fabricated by the conventional solid-state method. The effects of ZnO addition on their microstructure and piezoelectric properties were systematically investigated. The rhombohedral-tetragonal phase coexistence has been found in the ceramics without ZnO content and then with further increasing ZnO content, specimens exhibited tetragonal phase. The optimized ZnO content formed liquid phase and aided the grain growth of specimens. When 0.4 wt% ZnO was added, the optimal physical properties ($d_{33}=422pC/N$, $d_{31}=161pC/N$, ${\varepsilon}_r=1,905$, $k_p=0.55$, $Q_m=160$) were obtained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.202-206
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• 2007

ZnO is a promising material to make high efficient ultraviolet(UV) or blue light emitting diodes(LEDs) because of its large binding energy and energy bandgap. In this study, we prepared ZnO thin films with p-type conductivity on silicon(100) substrates by RF magnetron sputtering in the mixture of $N_2$ and $O_2$. The process was accompanied by low pressure in-situ annealing in $O_2$ at $600^{\circ}C$ and $800^{\circ}C$ respectively. Hall effect in Van der Pauw configuration showed that the N-doped ZnO film annealed at $800^{\circ}C$ has p-type conductivity. Photoluminescence(PL) spectrum of the film annealed at $800^{\circ}C$ showed UV emission related to exciton and bound to donor-acceptor pair(DAP) as well as visible emission related to many intrinsic defects.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.424-424
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• 2012

ZnO는 수열합성법을 통해 저온에서 단결정으로 성장할 수 있기 때문에 광전소자 및 압전소자로 응용되고 있으나, 성장된 ZnO nanowire 내부 산소 결함 및 표면에 OH기의 흡착에 의해 소자특성 저하를 발생시킨다. 본 연구에서는 ZnO의 결함의 최소화를 위해 Glass 기판에 수열합성법으로 성장된 ZnO nanowire를 ICP 플라즈마 장치를 이용하여 O2 25 sccm, Base Pressure $1.5{{\times}}10^{-3}$ Torr을 기준으로 파워와 시간에 따라 표면처리 하였다. 플라즈마 처리된 ZnO nanowire의 결함특성과 형상을 XPS와 FE-SEM를 통하여 분석하였으며, ZnO nanowire의 소자특성을 평가를 위해 Kapton Film/AZO/ZnO nanowire/PMMA/Au 구조의 발전기를 제작하였다. 150 W, 10 min에서 532.4 eV의 -OH결합이 최소화됨을 확인하였으며, 이를 이용하여 Flexible ZnO nanowire 발전기 제작 했을 경우 최대 Voltage 5 V, Current 156 nA 전기적 특성을 확인하였다.

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.651-651
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• 2000

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.297.2-297.2
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• 2013

Scavenging electricity from wasteful energy resources is currently an important issue and piezoelectric nanogenerators (NGs) based on zinc oxide (ZnO) are promising energy harvesters that can be adapted to various portable, wearable, self-powered electronic devices. Although ZnO has several advantages for NGs, the piezoelectric semiconductor material ZnO generate an intrinsic piezoelectric potential of a few volts as a result of its mechanical deformation. As grown, ZnO is usually n-type, a property that was historically ascribed to native defects. Oxygen vacancies (Vo) that work as donors exist in ZnO thin film and usually screen some parts of the piezoelectric potential. Consequently, the ZnO NGs' piezoelectric power cannot reach to its theoretical value, and thus decreasing the effect from Vo is essential. In the present study, c-axis oriented insulator-like sputtered ZnO thin films were grown in various temperatures to fabricate an optimized nanogenerator (NGs). The purity and crystalinity of ZnO were investigated with photoluminescence (PL). Moreover, by introducing a p-type polymer usually used in organic solar cell, it was discussed how piezoelectric passivation effect works in ZnO thin films having different types of defects. Prepared ZnO thin films have both Zn vacancies (accepter like) and oxygen vacancies (donor like). It generates output voltage 20 time lager than n-type dominant semiconducting ZnO thin film without p-type polymer conjugating. The enhancement is due to the internal accepter like point defects, zinc vacancies (VZn). When the more VZn concentration increases, the more chances to prevent piezoelectric potential screening effects are occurred, consequently, the output voltage is enhanced. Moreover, by passivating remained effective oxygen vacancies by p-type polymers, we demonstrated further power enhancement.

• Korean Journal of Materials Research
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• v.32 no.10
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• pp.435-441
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• 2022

We report the synthesis and gas sensing properties of bare and ZnO decorated TeO₂ nanowires (NWs). A catalyst assisted-vapor-liquid-solid (VLS) growth method was used to synthesize TeO₂ NWs and ZnO decoration was performed using an Au-catalyst assisted-VLS growth method followed by a subsequent heat treatment. Structural and morphological analyses using X-ray diffraction (XRD) and scanning/transmission electron microscopies, respectively, demonstrated the formation of bare and ZnO decorated TeO₂ NWs with desired phase and morphology. NO₂ gas sensing studies were performed at different temperatures ranging from 50 to 400 ℃ towards 50 ppm NO₂ gas. The results obtained showed that both sensors had their best optimal sensing temperature at 350 ℃, while ZnO decorated TeO₂ NWs sensor showed much better sensitivity towards NO₂ relative to a bare TeO₂ NWs gas sensor. The reason for the enhanced sensing performance of the ZnO decorated TeO₂ NWs sensor was attributed to the formation of ZnO (n)/ TeO₂ (p) heterojunctions and the high intrinsic gas sensing properties of ZnO.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.811-816
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• 2012

The effect of co-sputtering condition on the structural properties of $Mg_xZn_{1-x}O$ thin films grown by RF magnetron co-sputtering system was investigated for manufacturing ZnO/MgZnO structure LED. $Mg_xZn_{1-x}O$ thin films were grown with ZnO and MgO target varying RF power. Structural properties were investigated by X-ray diffraction (XRD) and Energy dispersive spectroscopy (EDS). The ZnO thin films have sufficient crystallinity on the high RF power. As RF power of ZnO target increased, the contents of MgO in the $Mg_xZn_{1-x}O$ film decreased. LED was manufactured using ZnO/MgZnO multi-layer on p-GaN/$Al_2O_3$ substrate. Threshold voltage of multi-layer LED was appeared at 8 V, and it was luminesced at wave length of 550 nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.121-121
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• 2008

We propose a novel nanomaterial-based pn diode which constructed with an n-type ZnO nanowire (NW) and a p-type HgTe nanoparticle (NP) thin film. The photo current characteristics of a ZnO NW, a HgTe NP thin film and pn diode constructed with a ZnO NW and a HgTe NP thin film were investigated under illumination of the 325 nm and 633 nm wavelength light. The conductivities of a ZnO NW exposed to the 325 nm and 633 nm wavelength light increased, while the photocurrents taken from the HgTe NP thin film was very close to the dark currents. Moreover, The pn diode exhibited the rectifying characteristics of the dark current and of the photocurrent excited by the 633 nm wavelength light. In contrast, the ohmic characteristics for the photocurrent were observed due to the junction barrier lowering in the conduction band of the ZnO nanowire under the illumination of the 325 nm wavelength light.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.354-354
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• 2011

ZnO 나노와이어는 밴드 갭이 3.37 ev로 큰 밴드 갭을 갖는 물질이며 엑시톤 결합에너지가 60 meV로 GaN(25 meV)같은 다른 반도체보다 매우 크다. 또한 밴드갭 에너지가 큰 GaN, SiC와 같은 반도체에 비해서 화학적, 열적 안정성이 크며 낮은 온도에서 성장이 가능하다는 장점이 있다. 본 연구에서는 pre-heating process를 이용하여 1차원 구조인 ZnO nanowire를 수열합성법으로 합성하였다. 실험방법으로는 E2K glass 기판위에 AZO40 nm를 증착후, 시드층으로 이용하여 ZnO nanowire를 성장하였다. precusor 전구체에는 ZN(NO3)2 ${\cdot}$ 6H2O와 Capping agent으로의 역할을 위해 PEI와 OH-source 공급을 위한 Ammonium chloride를 첨가하여 합성하였고, 그에 따른 ZnO nanowire의 morphology 및 aspect ratio를 조절하고자 하였다. 마지막으로 ZnO 나노와이어의 구조적, 광학적 특성 평가를 하기위해 XRD, FE-SEM, PL 등을 이용하여 측정 하였고, 향후 나노발전기, 태양전지 등 여러 광학기기 등에 전극재료로서 응용 가능성에 대해 알아보고자 하였다.

• 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.