• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.207.2-207.2
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• 2013

Oxide-based thin film transistors have been attempted as powerful candidates for driving circuits for active-matrix organic light-emitting diodes and transparent electronics. The oxide TFTs are based on the amorphous multi-component oxides involving zinc, indium, and/or tin elements as main cation sources. The current work employed RF sputtering in order to deposit zinc-tin oxide thin films applicable to transparent oxide thin film transistors. The deposited thin film was characterized and probed in terms of materials and devices. The physical/chemical characterizations were performed using X-ray diffraction, Atomic Force Microscopy, Spectroscopic Ellipsometry, and X-ray Photoelectron Spectroscopy. The thin film transistors were fabricated using a bottom-gated structure where thermally-grown silicon oxide layers were applied as gate-dielectric materials. The inherent properties of oxide thin films are combined with the corresponding device performances with the aim to fabricating the multi-component oxide thin films being optimized towards transparent electronics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.9
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• pp.798-801
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• 2007

Multilayer transparent electrodes, having a much lower electrical resistance than the widely used transparent conducting oxide electrodes, were prepared by using radio frequency magnetron sputtering. The multilayer structure consisted of five layers, indium tin oxided (ITO)/zinc oxide (ZnO)/Ag/zinc oxide (ZnO)/ITO. With about 50 nm thick ITO films, the multilayer showed a high optical transmittance in the visible range of the spectrum and had color neutrality. The electrical and optical properties of ITO/ZnO/Ag/ZnO/ITO multilayer were changed mainly by Ag film properties, which were affected by the deposition process of the upper layer. Especially ZnO layer was improved to adhesion of Ag and ITO. A high quality transparent electrode, having a resistance as low as and a high optical transmittance of 91% at 550 nm, was obtained. It could satisfy the requirement for the flexible OLED and LCD.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.397-397
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• 2007

Multilayer transparent electrodes, having a much lower electrical resistance than the widely used transparent conducting oxide electrodes, were prepared by using radio frequency magnetron sputtering. The multilayer structure consisted of five layers, indium tin oxided(ITO)/zinc oxide(ZnO)/Ag/oxide(ZnO)/ITO. With about 50nm thick ITO films, the multilayer showed a high optical transmittance in the visible range of the spectrum and had color neutrality. The electrical and optical properties of ITO/ZnO/Ag/ZnO/ITO multilayer were changed mainly by Ag film properties, which were affected by the deposition process of the upper layer. Especially ZnO layer was improved to adhesion of Ag and ITO. A high quality transparent electrode, having a resistance as low as and a high optical transmittance of 91% at 550nm, was obtained. It could satisfy the requirement for the flexible OLED and LCD.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.273.2-273.2
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• 2014

Sputtering process has been widely used in Si-based semiconductor industry and it is also an ideal method to deposit transparent oxide materials for thin-film transistors (TFTs). The oxide films grown at low temperature by conventional RF sputtering process are typically amorphous state with low density including a large number of defects such as dangling bonds and oxygen vacancies. Those play a crucial role in the electron conduction in transparent electrode, while those are the origin of instability of semiconducting channel in oxide TFTs due to electron trapping. Therefore, post treatments such as high temperature annealing process have been commonly progressed to obtain high reliability and good stability. In this work, the scheme of electron-assisted RF sputtering process for high quality transparent oxide films was suggested. Through the additional electron supply into the plasma during sputtering process, the working pressure could be kept below $5{\times}10-4Torr$. Therefore, both the mean free path and the mobility of sputtered atoms were increased and the well ordered and the highly dense microstructure could be obtained compared to those of conventional sputtering condition. In this work, the physical properties of transparent oxide films such as conducting indium tin oxide and semiconducting indium gallium zinc oxide films grown by electron-assisted sputtering process will be discussed in detail. Those films showed the high conductivity and the high mobility without additional post annealing process. In addition, oxide TFT characteristics based on IGZO channel and ITO electrode will be shown.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.242-248
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• 2014

Flexibility of a transparent device has been required in accordance with miniaturization and mobilization needs in recent industry. The most representative material used as a transparent electrode is indium tin oxide (ITO). However, a couple of disadvantages of ITO are the exhaustion of natural resource of indium and its inflexibility due to inorganic substance. To overcome the limit of ITO, a variety of alternative materials have been researched on development of transparent electrodes and its properties through composite materials. In this review, we classify some of emerged materials with their general studies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.183-183
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• 2009

본 연구에선 ITO에 사용되는 Indium의 양을 줄이기 위해 ITO와 유사한 성질을 보이는 조성인 Indium - Zinc - Tin Turnary compound를 연구하였다. 각 조성은 Indium - Zinc - Tin Turnary compound를 기본으로 하여 Zinc site에 이종원소인 Al2O3와 Ga2O3를 doping함에 따라 변화되는 전기적 특성을 살며보았다. 분석에 사용한 Ceramic pellet은 일반적인 Ceramic process를 거쳐 제작되었다. 각 조성의 전기적 특성은 TCR meter와 Hall effect analyser를 이용하여 측정하였고, X-ray diffraction measurements(XRD), Scanning Electron microscope(SEM)를 이용하여 결정학적 특성을 분석하였다.

• Ceramist
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• v.21 no.1
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• pp.12-23
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• 2018

As the flexible displays have been considered as a breakthrough to make a new electronics category, transparent electrodes have also confronted with an emerging issue, i.e., they also need to be mechanically flexible. For this to be made possible, a transparent electrode capable of withstanding large amounts of strain must be developed. Indium tin oxide (ITO) has been one of the most widely adopted transparent electrodes for displays and other transparent electronics, mainly supported by its high electrical conductivity and optical transparency. However, its brittle nature has forced the display industry to search for other alternatives. Recently, advances in nano-material researches have opened the door for various transparent conductive materials, which include carbon nanotube, graphene, Ag and Cu nanowire, and printable metal grids. Here we reviewed recently-published research works introducing flexible displays, all of which are employing the novel candidates for a conducting material.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.187-187
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• 2015

The past thirty years have seen increasingly rapid advances in the field of Indium Tin Oxide (ITO) transparent thin film.[1] However, a major problem with this ITO thin film application is high cost compared with other transparent thin film materials.[2] So far, in order to overcome this disadvantage, we show a transparent ITO/Ag/i-ZnO multilayer thin film electrode can be the solution. In comparison with using amount of ITO as a transparent conducting material, intrinsic-Zinc-Oxide (i-ZnO) based on ITO/Ag/i-ZnO multilayer thin film showed cost-effective and it has not only highly transparent but also conductive properties. The aim of this research has therefore been to try and establish how ITO/Ag/i-ZnO multilayer thin film would be more effective than ITO thin film. Herein, we report ITO/Ag/i-ZnO multilayer thin film properties by using optical spectroscopic method and measuring sheet resistance. At a certain total thickness of thin film, sheet resistance of ITO/Ag/i-ZnO multilayer was drastically decreased than ITO layer approximately $40{\Omega}/{\square}$ at same visible light transmittance.(minimal point $5.2{\Omega}/{\square}$). Tendency, which shows lowly sheet resistive in a certain transmittance, has been observed, hence, it should be suitable for transparent electrode device.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.209-209
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• 2012

High-efficient transparent conductive oxide (TCO) film-embedding Si heterojunction solar cells were fabricated. An additional doping was not applied for heterojunction solar cells due to the spontaneous junction formation between TCO films and an n-type Si substrate. Three different TCO coatings were formed by sputtering method for an Al-doped ZnO (AZO) film, an indium-tin-oxide (ITO) film and double stacks of ITO/AZO films. An improved crystalline ITO film was grown on an AZO template upon hetero-epitaxial growth. This double TCO films-embedding Si heterojunction solar cell provided significantly enhanced efficiency of 9.23% as compared to the single TCO/Si devices. The effective arrangement of TCO films (ITO/AZO) provides benefits of a lower front contact resistance and a smaller band offset to Si leading enhanced photovoltaic performances. This demonstrates a potential scheme of the effective TCO film-embedding heterojunction Si solar cells.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.609-614
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• 2014

We fabricated amorphous zinc tin oxide (ZTO) transparent thin-film transistors (TTFTs). The effects of Al electrode on the mobility and threshold voltage of the ZTO TTFTs were investigated. It was found that the aluminum (Al)-ZTO contact decreased the mobility and increased the threshold voltage. Traps, originating from $AlO_x$, were assumed to be the cause of degradation. An indium tin oxide film was inserted between Al and ZTO as a buffer layer, forming an ohmic contact, which was revealed to improve the performance of ZTO TTFTs.