• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.151-151
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• 2009

Recently, there has been increasing interest in amorphous oxide semiconductors to find alternative materials for an amorphous silicon or organic semiconductor layer as a channel in thin film transistors(TFTs) for transparent electronic devices owing to their high mobility and low photo-sensitivity. The fabriction of amorphous oxide-based TFTs at room temperature on plastic substrates is a key technology to realize transparent flexible electronics. Amorphous oxides allows for controllable conductivity, which permits it to be used both as a transparent semiconductor or conductor, and so to be used both as active and source/drain layers in TFTs. One of the materials that is being responsible for this revolution in the electronics is indium-zinc-tin oxide(IZTO). Since this is relatively new material, it is important to study the properties of room-temperature deposited IZTO thin films and exploration in a possible integration of the material in flexible TFT devices. In this research, we deposited IZTO thin films on polyethylene naphthalate substrate at room temperature by using magnetron sputtering system and investigated their properties. Furthermore, we revealed the fabrication and characteristics of top-gate-type transparent TFTs with IZTO layers, seen in Fig. 1. The experimental results show that by varying the oxygen flow rate during deposition, it can be prepared the IZTO thin films of two-types; One a conductive film that exhibits a resistivity of $2\times10^{-4}$ ohm${\cdot}$cm; the other, semiconductor film with a resistivity of 9 ohm${\cdot}$cm. The TFT devices with IZTO layers are optically transparent in visible region and operate in enhancement mode. The threshold voltage, field effect mobility, on-off current ratio, and sub-threshold slope of the TFT are -0.5 V, $7.2\;cm^2/Vs$, $\sim10^7$ and 0.2 V/decade, respectively. These results will contribute to applications of select TFT to transparent flexible electronics.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.10
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• pp.1011-1017
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• 2012

We report the development of an optical micro-nanolithography method by using a roll-type mask. It includes phase-shift lithography and photolithography for realizing various target dimensions. For sub-wavelength resolution, a structure is achieved using the near-field exposure of a photoresist through a cylindrical phase-mask, allowing high-throughput continuous patterning. By using a film-type metal mask, continuous photolithography was achieved, and this method could be used to control the period of resultant patterns in real time by changing the rotating speed of the cylinder mask. As an application, we present the fabrication of a transparent electrode in the form of a metallic mesh by using the developed roll-type photolithography process. As a result, a transparent conductor with good properties was achieved by using a recently built cylindrical phase-shift lithography prototype, which was designed for patterning on 100-mm2 substrates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.857-860
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• 2003

Tin doped indium oxide(ITO) and Al doped zinc oxide(ZnO:Al) films, which are widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. The electrical and optical properties of both the ITO and ZnO:Al thin films were investigated as functions of substrate temperature, working gas pressure and deposition time. ITO and ZnO:Al films with the the present experimental conditions of temperature and pressure showed resistivity of $2.36{\times}10^{-4}{\Omega}-cm,\;9.42{\times}10^{-4}{\Omega}-cm$ and transmittance of 86.28%, 90.88% in the wavelength range of the visible spectrum, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.969-972
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• 2004

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. In this paper the effect of doping amounts of $Al_2O_3$ on the electrical, optical and morphological properties were investigated experimentally, The results show that the structural and electrical properties of the film are highly affected by the doping. The optimum growth conditions were obtained for films doped with 2 wt% of Al203 which exhibit a resistivity of $8.5{\times}10^{-4}{\Omega}-cm$ associated with a transmittance of 91.7 % for 840 nm in film thickness in the wavelength range of the visible spectrum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.143-146
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• 2003

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. The influence of the substrate temperature, working gas pressure and discharge power on the electrical, optical and morphological properties were investigated experimentally. The consideration on the effect of doping amounts of Al on the electrical and optical properties of ZnO thin film were also carried out. ZnO:Al films with the optimum growth conditions showed resistivity of $9.42{\times}10^{-4}\;{\Omeg}-cm$ and transmittance of 90.88% for 840nm in film thickness in the wavelength range of the visible spectrum.

• Korean Journal of Materials Research
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• v.14 no.5
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• pp.328-333
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• 2004

Transparent ZnO:Al conductor films for the optoelectronic devices were deposited by using the capacitively coupled DC magnetron sputtering method. The effect of Al doping concentration and discharge power on the electrical and optical properties of the films was studied. The film resistivity of $8.5${\times}$10^{-4}$ $\Omega$-cm was obtained at the discharge power of 40 W with the ZnO target doped with 2 wt% $Al_2$$_O3$. The transmittance of the 840 nm thick film was 91.7% in the visible waves. Increasing doping concentration of 3 wt% $Al_2$$O_3$ in ZnO target results in significant decrease of film resistivity, which may be due to the formation of $Al_2$$O_3$ particles in the as-deposited ZnO:Al film and the reduced ZnO grain sizes. Increasing DC power from 40 to 60 W increases deposition rate by more than 50%, but can induce high defect density in the film, resulting in higher film resistivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.408-411
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• 2003

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. The influence of the substrate temperature, working gas pressure, discharge power and doping amounts of Al on the electrical, optical and morphological properties were investigated experimentally. The effect of bias voltage on the electrical properties of ZnO thin film were also studied. Films with lowest resistivity of $5.4{\times}10^{-4}\;{\Omega}-cm$ have been achieved in case of films deposited at 1mtorr, $400^{\circ}C$ with a substrate bias of +10V for 840nm in film thickness.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.939-942
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• 2004

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors were Prepared by using the capacitively coupled RF magnetron sputtering method. In this paper the effect of RF discharge power on the electrical, optical and structural properties were investigated experimentally. The results show that the structural and electrical properties of the film are highly affected by the variation of RF discharge power. The optimum growth conditions were obtained for films doped with 2 wt% of $Al_2O_3$ and 200 W in RF discharge power, which exhibit a resistivity of $10.4{\times}10^{-4}{\Omega}-cm$ associated with a transmittance of 89.66 % for 1000nm in films thickness in the wavelength range of the visible spectrum.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.3
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• pp.165-170
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• 2018

In this study, double-layered TCO (transparent conductive oxide) films were produced by depositing two distinct TCO materials: $SnO_2$ works as an n-type layer and ITO (indium-doped tin oxide) serves as a transparent conductor. Both transparent conductive oxide-films were sequentially deposited by sputtering. The electrical and optical properties of single-layered TCO films ($SnO_2$) and double-layered TCO ($ITO/SnO_2$) films were investigated. A TCO-embedding photodetector was realized through the formation of an $ITO/SnO_2/p-Si/Al$ layered structure. The remarkably high rectifying ratio of 400.64 was achieved with the double-layered TCO device, compared to 1.72 with the single-layered TCO device. This result was attributed to the enhanced electrical properties of the double-layered TCO device. With respect to the photoresponses, the photocurrent of the double-layered TCO photodetector was significantly improved: 1,500% of that of the single-layered TCO device. This study suggests that, due to the electrical and optical benefits, double-layered TCO films are effective for enhancing the photoresponses of TCO photodetectors. This provides a useful approach for the design of photoelectric devices, including solar cells and photosensors.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1087-1090
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• 2008

This paper presents the electro-luminescence (EL) display lamp which is patterned on a curved surface by the pad printing method. The printing methods, including the gravure, screen, flexo, inkjet, and pad printing, have an advantage of one-step direct patterning. However, in general, the printing and semi-conductor process, except pad printing method, cannot be applied for patterning on a curved surface. Thus, in this paper, we used pad printing method for patterning an EL display lamp on a curved surface. The EL display lamp consists of 5 layers: Bottom electrode; Dielectric layer; Phosphor; Transparent electrode; Bus electrode. Finally, we printed EL display lamp on a dish, which has a radius of curvature 80mm. The EL display lamp was driven at AC 200V of 1kHz.