• ETRI Journal
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• v.31 no.6
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• pp.636-641
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• 2009

ZnO nanofibers were electro-spun from a solution containing poly 4-vinyl phenol and Zn acetate dihydrate. The calcination process of the ZnO/PVP composite nanofibers brought forth a random network of polycrystalline wurtzite ZnO nanofibers of 30 nm to 70 nm in diameter. The electrical properties of the ZnO nanofibers were governed by the grain boundaries. To investigate possible applications of the ZnO nanofibers, their CO and $NO_2$ gas sensing responses are demonstrated. In particular, the $SnO_2$-deposited ZnO nanofibers exhibit a remarkable gas sensing response to $NO_2$ gas as low as 400 ppb. Oxide nanofibers emerge as a new proposition for oxide-based gas sensors.

• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.420-426
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• 2020

A metal oxide semiconductor gas sensor is operated by measuring the changes in resistance that occur on the surface of nanostructures for gas detection. ZnO, which is an n-type metal oxide semiconductor, is widely used as a gas sensor material owing to its high sensitivity. Various ZnO nanostructures in gas sensors have been studied with the aim of improving surface reactions. In the present study, the sol-gel and vapor phase growth techniques were used to fabricate nanostructures to improve the sensitivity, response, and recovery rate for gas sensing. The sol-gel method was used to synthesize SnO₂ nanoparticles, which were used as the seed layer. The nanoparticles size was controlled by regulating the process parameters of the solution, such as the pH of the solution, the type and amount of solvent. As a result, the SnO₂ seed layer suppressed the aggregation of the nanostructures, thereby interrupting gas diffusion. The ZnO nanostructures with a sol-gel processed SnO₂ seed layer had larger specific surface area and high sensitivity. The gas response and recovery rate were 1-7 min faster than the gas sensor without the sol-gel process. The gas response increased 4-24 times compared to that of the gas sensor without the sol-gel method.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.47-53
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• 2005

The E.M.F. of the galvanic cell with fused salt was measured to determine the activities of zinc at 720-860 K over the entire composition range of liquid Zn-In and Zn-Sn alloys. The cell used was as follows: $$(-)W{\mid}Zn(pure){\mid}Zn^{2+}(KCl-LiCl){\mid}Zn(in\;Zn-In\;or\;Zn-Sn\;alloy){\mid}W(+)$$ The activities of zinc in the alloys showed positive deviation from Raoult's law over the entire composition range. The activity of cadmium and some thermodynamic functions such as Gibbs free energy, enthalpy and entropy were derived from the results by the thermodynamic relationship. The comparison of the results and the literature data was made. The liquid Zn-In and Zn-Sn alloys are found to be close tn the regular solution. The concentration fluctuations in long wavelength limit, $S_{cc}(o)$, in the liquid alloy were calculated from the experimental results.

• Transactions on Electrical and Electronic Materials
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• v.10 no.5
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• pp.169-172
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• 2009

The ZnO/CuSn/ZnO (ZCSZ) multilayer films were deposited on polycarbonate substrates using reactive RF and DC magnetron sputtering. The thickness of each layer was 50 nm/5 nm/45 nm, respectively. The ZCSZ films showed a sheet resistance of $44{\Omega}$/Sq, which was an order of magnitude lower than that indium tin oxide (ITO) films. Although the ZCSZ films had a CuSn interlayer that absorbed visible light, both films had similar optical transmittances of 74% in the visible wavelength region. The figure of merit of the ZCSZ films was $1.0{\times}10^{-3}{\Omega}^{-1}$ and was greater than the value of the ITO films, $1.6{\times}10^{-4}{\Omega}^{-1}$. From the X-ray diffraction (XRD) analysis, the ITO films did not show any diffraction peaks, whereas the ZCSZ films showed diffraction peaks for the ZnO (100) and (002) phases. The hardness of the ITO and ZCSZ films were 5.8 and 7.1 GPa, respectively, which were determined using nano-indentation. From these results, the ZCSZ films exhibited greater optoelectrical performance and hardness compared to the conventional ITO films.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.334-334
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• 2012

Transparent oxide semiconductors have recently attracted much attention as channel layer materials due to advantageous electrical and optical characteristics such as high mobility, high stability, and good transparency. In addition, transparent oxide semiconductor can be fabricated at low temperature with a low production cost and it permits highly uniform devices such as large area displays. A variety of thin film transistors (TFTs) have been studied including ZnO, InZnO, and InGaZnO as the channel layer. Recently, there are many studies for substitution of Ga in InGaZnO TFTs due to their problem, such as stability of devices. In this work, new quaternary compound materials, tantalum-indium-tin oxide (TaInSnO) thin films were fabricated by using co-sputtering and used for the active channel layer in thin film transistors (TFTs). We deposited TaInSnO films in a mixed gas (O2+Ar) atmosphere by co-sputtering from Ta and ITO targets, respectively. The electric characteristics of TaInSnO TFTs and thin films were investigated according to the RF power applied to the $Ta_2O_5$ target. The addition of Ta elements could suppress the formation of oxygen vacancies because of the stronger oxidation tendency of Ta relative to that of In or Sn. Therefore the free carrier density decreased with increasing RF power of $Ta_2O_5$ in TaInSnO thin film. The optimized characteristics of TaInSnO TFT showed an on/off current ratio of $1.4{\times}108$, a threshold voltage of 2.91 V, a field-effect mobility of 2.37 cm2/Vs, and a subthreshold swing of 0.48 V/dec.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.79-79
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• 2009

Samples of Ta-doped in $In_2O_3-ZnO-SnO_2$(IZTO) with a doping level up to 4wt% were sintered at $1600^{\circ}C$ in $O_2$. The crystal phase of the samples was identified by an X-ray diffraction experiment. apparent density and porosity with sintered temperature from $1500^{\circ}C$ to $1640^{\circ}C$ are mesured by archimedes method. For each sample, the specific resistivity was determined. samples of sintered at $1600^{\circ}C$ had the highest density and lowest porousity and The Ta 0.25-wt%-doped IZTO ceramics had the lowest resistivity.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.663-668
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• 2012

In order to reduce the indium contents in transparent conducting oxide(TCO) thin films of $In_{1.6{\sim}1.8}Zn_{0.2}Sn_{0.2{\sim}0.4}O_3$ (IZTO), $In_{1.6}Zn_{0.2}Sn_{0.2}O_{3-{\delta}}$(IZTO) was prepared by replacing indium with Zn and Sn. The TCO films were deposited via RF-magnetron sputtering of the IZTO target at various deposition temperatures and its film characteristics were investigated. When deposited in an Ar atmosphere at $400^{\circ}C$, the electrical resistivity of the film decreased to $6.34{\times}10^{-4}{\Omega}{\cdot}cm$ and the optical transmittance was 80%. As the deposition temperature increased, the crystallinity of the IZTO film was enhanced. As a result, the electrical conductivity and transmittance properties were improved. This demonstrates the possibility of replacing ITO TCO film with IZTO.

• Journal of the Korean Magnetics Society
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• v.2 no.2
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• pp.99-104
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• 1992

The permeability vs. temperature curve, the loss factor and the microstructure of a commercial Mn-Zn ferrites were investigated by X-ray diffractometer, SEM and LCR meter, where the additives, such as $SnO_{2}$ and $GeO_{2}$, were added to the main composition. Their wt% were 0.05, 0.3 and 1.0, respectively. When the content of additives increased, the SPM (Secondary Peak Maximum) of the permeability moved from $80^{\circ}C$ to below the room temperature. This movement, without the significant change of the microstructure, is because Sn and Ge, having the different ionic radius, were soluble in the matrix. There was no variation of the permeability with the frequency up to 100 kHz. And the loss factor showed the maximum value at 10 kHz.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.91-92
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• 2007

In-Sn-Zn-O (ISZO)박막과 In-Zn-Sn-O (IZSO)박막은 상온에서 2개의 캐소드 (DC, RF)를 이용하여 마그네트론 2원 동시 방전법에 의해 polyethylene terephthalate (PET)기판 위에 실온에서 증착되었다. ISZO 박막의 경우, Zn함량이 증가함에 따라 비저항은 증가하였지만, Zn원자의 도입에 의해 표면 조도는 개선되었다. 반면, IZSO 박막의 경우, 최저비저항 ($3.17$ ${\times}$ $10^{-4}$ ${\Omega}cm$)은 $SnO_2$ 타켓의 RF power 40W에서 얻어졌지만, Sn원자의 도입에 의해 표면 조도는 거칠어졌다. XRD 측정 결과 모든 박막은 비정질 구조로 사료되고, 가시광선 영역에서 80% 이상의 높은 투과율을 보였다.

• Korean Journal of Metals and Materials
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• v.48 no.9
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• pp.861-866
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• 2010

Tetrapod-shaped ZnO crystals were synthesized through a simple oxidation of metallic Zn powder in air without the presence of any catalysts or substrates. X-ray diffraction data revealed that the ZnO crystals had wurtzite structure. It is supposed that the growth of the tetrapod proceeded in a vapor-solid growth mechanism. As the amount of the source powder increased, the size of the tetrapod decreased. The tip morphology of the tetrapod changed from a needle-like shape to a spherical shape with the oxidation time. ZnO crystals with rod shape were fabricated via the oxidation of Zn and Sn mixture. Sn played an important role in the formation of ZnO crystals with different morphology by affecting the growth mode of ZnO crystals. The cathodoluminescent properties were measured for the samples. The strongest green emission was observed for the rod-shaped ZnO crystals, suggesting that the crystals had the high density of oxygen vacancies.