• ETRI Journal
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• v.13 no.2
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• pp.21-27
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• 1991

Effects of annealing on the dielectric properties and microstructures of thin tantalum oxide film(25nm) deposited on p-type Si substrate with rf reactive magnetron sputtering were investigated. The leakage current density was remarkably reduced from $10^-8$ to $10^-12$ A/$\mum^2$at the electric field of 2MV/cm after rapid thermal annealing(RTA) in $O_2$at $1000^{\circ}C$, while little leakage reduction was observed after furnace annealing in $O_2$ at $500^{\circ}C$. The structural changes of thin tantalum oxide film after annealing were examined using high resolution electron microscope(HREM). The results of HREM show that substantial reduction in the leakage current density after the RTA in $O_2$ can be attributed to crystallization and reoxidation of the thin amorphous tantalum oxide film.

• 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.

• Journal of Information Display
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• v.11 no.4
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• pp.165-168
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• 2010

A solution-processed multicomponent oxide, yttrium hafnium zinc oxide (YHZO), was synthesized and deposited as a gate insulator. The YHZO film annealed at $600^{\circ}C$ contained an amorphous phase based on the results of thermogravimetry, differential thermal analysis, and X-ray diffraction. The electrical characteristics of the YHZO film were analyzed by measuring the leakage current. The high dielectric constant (16.4) and high breakdown voltage (71.6 V) of the YHZO films resulted from the characteristics of $HfO_2$ and $Y_2O_3$, respectively. To examine if YHZO can be applied to thin-film transistors (TFTs), indium gallium zinc oxide TFTs with a YHZO gate insulator were also fabricated. The desirable characteristics of the YHZO films when used as a gate insulator show that the limitations of the general binary-oxide-based materials and of the conventional vacuum processes can be overcome.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.276-276
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• 2014

High-performance, fully-transparent, and top-gated oxide thin-film transistor (TFT) was successfully fabricated with Ta2O5 high-k gate dielectric on a glass substrate. Through a self-passivation with the gate dielectric and top electrode, the top-gated oxide TFT was not affected from H2O and O2 causing the electrical instability. Heat-treated InSnO (ITO) was used as the top and source/drain electrode with a low resistance and a transparent property in visible region. A InGaZnO (IGZO) thin-film was used as a active channel with a broad optical bandgap of 3.72 eV and transparent property. In addition, using a X-ray diffraction, amorphous phase of IGZO thin-film was observed until it was heat-treated at 500 oC. The fabricated device was demonstrated that an applied electric field efficiently controlled electron transfer in the IGZO active channel using the Ta2O5 gate dielectric. With the transparent ITO electrodes and IGZO active channel, the fabricated oxide TFT on a glass substrate showed optical transparency and high carrier mobility. These results expected that the top-gated oxide TFT with the high-k gate dielectric accelerates the realization of presence of fully-transparent electronics.

• Journal of the Korean institute of surface engineering
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• v.47 no.1
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• pp.7-12
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• 2014

The characteristics of oxidation for the Zry-4 was measured in the $800^{\circ}C$ and high steam pressure (50 bar, 75 bar, 100 bar) conditions, using an apparatus for high pressure steam oxidation. The effect of accelerated oxidation by high-pressure steam was increased more than 60% in hydrogen-charged cladding than normal cladding. This difference between hydrogen charged claddings and normal claddings tends to be larger as the higher pressure. The accelerated oxidation effect of hydrogen charging cladding is regarded as the hydrogen on the metal layer affects the formation of the protective oxide layer. The creation of the sound monoclinic phase in Zry-4 oxidation influences reinforcement of corrosion-resistance of the oxide layer. The oxidation is estimated to be accelerated due to the creation of equiaxial type oxide film with lower corrosion resistance than that of columnar type oxide film. When tetragonal oxide film transformed into the monoclinic oxide film, surface energy of the new monoclinic phase reduced by hydrogen in the metal layer.

• Korean Journal of Materials Research
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• v.25 no.4
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• pp.171-176
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• 2015

We present the detection characteristics of nitrogen monoxide(NO) gas using p-type copper oxide(CuO) thin film gas sensors. The CuO thin films were fabricated on glass substrates by a sol-gel spin coating method using copper acetate hydrate and diethanolamine as precursors. Structural characterizations revealed that we prepared the pure CuO thin films having a monoclinic crystalline structure without any obvious formation of secondary phase. It was found from the NO gas sensing measurements that the p-type CuO thin film gas sensors exhibited a maximum sensitivity to NO gas in dry air at an operating temperature as low as $100^{\circ}C$. Additionally, these CuO thin film gas sensors were found to show reversible and reliable electrical response to NO gas in a range of operating temperatures from $60^{\circ}C$ to $200^{\circ}C$. It is supposed from these results that the p-type oxide semiconductor CuO thin film could have significant potential for use in future gas sensors and other oxide electronics applications using oxide p-n heterojunction structures.

• Journal of the Korean institute of surface engineering
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• v.52 no.5
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• pp.258-264
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• 2019

Assembling heterostructures by combining dissimilar oxide semiconductors is a promising approach to enhance charge separation and transfer in photoelectrochemical (PEC) water splitting. In this work, the CuO nanorods array/$Cu_2O$ thin film bilayered heterostructure was successfully fabricated by a facile method that involved a direct electrodeposition of the $Cu_2O$ thin film onto the vertically oriented CuO nanorods array to serve as the photoelectrode for the PEC water oxidation. The resulting copper-oxide-based heterostructure photoelectrode exhibited an enhanced PEC performance compared to common copper-oxide-based photoelectrodes, indicating good charge separation and transfer efficiency due to the band structure realignment at the interface. The photocurrent density and the optimal photocurrent conversion efficiency obtained on the CuO nanorods/$Cu_2O$ thin film heterostructure were $0.59mA/cm^2$ and 1.10% at 1.06 V vs. RHE, respectively. These results provide a promising route to fabricating earth-abundant copper-oxide-based photoelectrode for visible-light-driven hydrogen generation using a facile, low-cost, and scalable approach of combining electrodeposition and hydrothermal synthesis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.170-174
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• 2023

Nickel oxide is a nonstoichiometric transparent conductive oxide with p-type conductivity, a wide-band energy gap of 3.4~4.0 eV, and excellent chemical stability, making it a very important candidate as a material for bipolar devices. P-type conductivity in Transparent Conductive Oxides (TCO) is controlled by the oxygen vacancy concentration. During the TCO film deposition process, additional oxygen diffusing into the NiO structure causes the formation of Ni 3p ions and Ni vacancies. This eventually affects the hole concentration of the p-type oxide thin film. In this work, the surface morphology and the electrical characteristics were confirmed in accordance with the annealing atmosphere of the nickel oxide thin film.

• Corrosion Science and Technology
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• v.22 no.6
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• pp.399-407
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• 2023

This study investigated the formation of oxide films on 6061 aluminum (Al) alloy and their impacts on corrosion resistance efficiency by regulating anodization voltage. Despite advantageous properties inherent to Al alloys, their susceptibility to corrosion remains a significant limitation. Thus, enhancing corrosion resistance through developing protective oxide films on alloy surfaces is paramount. The first anodization was performed for 6 h with an applied voltage of 30, 50, or 70 V on the 6061 Al alloy. The second anodization was performed for 0.5 h by applying 40 V after removing the existing oxide film. Resulting oxide film's shape and roughness were analyzed using field emission-scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Wettability and corrosion resistance were compared before and after a self-assembled monolayer (SAM) using an FDTS (1H, 1H, 2H, 2H-Perfluorodecyltrichlorosilane) solution. As the first anodization voltage increased, the final oxide film's thickness and pore diameter also increased, resulting in higher surface roughness. Consequently, all samples exhibited superhydrophilic behavior before coating. However, contact angle after coating increased as the first anodization voltage increased. Notably, the sample anodized at 70 V with superhydrophobic characteristics after coating demonstrated the highest corrosion resistance performance.

• Corrosion Science and Technology
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• v.20 no.5
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• pp.256-265
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• 2021

Titanium is applied in various industries due to its valuable properties and abundant reserves. Generally, if a highly uniform oxide structure and a high-density oxide film is formed on the surface through anodization treatment, the utility value such as color appearance and corrosion inhibition efficiency is further increased. The objective of this study was to determine improvement of water-repellent property by controlling titanium oxide parameters such as pore size and inter-pore distance to improve corrosion resistance. Oxide film structures of different shapes were prepared by controlling the anodization processing time and voltage. These oxide structures were then analyzed using a Field Emission Scanning Electron Microscope (FE-SEM). Afterwards, a Self-Assembled Monolayer (SAM) coating was performed for the oxide structure. The contact angle was measured to determine the relationship between the shape of the oxide film and the water-repellency. The smaller the solid fraction of the surface, the higher the water-repellent effect. The surface with excellent hydrophobic properties showed improved corrosion resistance. Such water-repellent surface has various applications. It is not only useful for corrosion prevention, but also useful for self-cleaning. In addition, a hydrophobic titanium may open up a new world of biomaterials to remove bacteria from the surface.