• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.224-224
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• 2010

Pt와 ITO 상부전극의 top-electode/NiO/Pt 구조에서 resistance switching현상을 연구하였다. 하부전극물질이 resistance switching현상에 미치는 영향은 이미 연구되었다. Ohmic 이나 low Schottky contact은 NiO 박막의 resistance switching 현상은 높은 전기장의 인가에 의해 것이 나타나는 것은 알 수 있었다. Ohmic contact에서는 유도전기장에 의한 resistance switching 현상들을 관찰할 수 있다. low Schottky barrier를 가지는 ITO/NiO/Pt 구조에서 resistances switching현상은 관찰되지 않고 Pt/ITO구조로 Ohmic 접촉은 유도전기장에 의한 resistance switching 현상이 나타나지 않음을 알 수 있었다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2265-2269
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• 2011

1 kV high-voltage GaN Schottky diode is realized using GaN-on-Si template by oxidizing Ni-Schottky contact. The Auger electron spectroscopy (AES) analysis revealed the formation of $NiO_x$ at the top of Schottky contact. The Schottky contact was changed to from Ni/Au to Ni/Ni-Au alloy/Au/$NiO_x$ by oxidation. Ni diffusion into AlGaN improves the Schottky interface and the trap-assisted tunneling current. In addition, the reverse leakage current and the isolation-leakage current are efficiently suppressed by oxidation. The isolation-leakage current was reduced about 3 orders of magnitudes. The reverse leakage current was also decreased from 2.44 A/$cm^2$ to 8.90 mA/$cm^2$ under -100 V-biased condition. The formed group-III oxides ($AlO_x$ and $GaO_x$) during the oxidation is thought to suppress the surface leakage current by passivating surface dangling bonds, N-vacancies and process damages.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.813-816
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• 2002

We investigate the junction between CdZnTe and a variety of metals with the aim of determining whether the choice of metal can improve the performance of X-ray image detectors, in particular minimizing the dark current. The samples consist of $5{\mu}m$ thick CdZnTe with top electrodes formed from In, Al, and Au. For each metal, current transients following application of valtages from -10V to 10V are measured for up to 1 hour. We find that dark currents depending on the metal used. The current is controlled by hole injection at the metal-CdZnTe junction and there is consistent trend with the metal's work function possibly and it seems that metal to CdZnTe layer junction is ohmic contact.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.67.1-67.1
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• 2012

Graphene has attracted much attention for future nanoelectronics due to its superior electrical properties. Owing to its extremely high carrier mobility and controllable carrier density, graphene is a promising material for practical applications, particularly as a channel layer of high-speed FET. Furthermore, the planar form of graphene is compatible with the conventional top-down CMOS fabrication processes and large-scale synthesis by chemical vapor deposition (CVD) process is also feasible. Despite these promising characteristics of graphene, much work must still be done in order to successfully develop graphene FET. One of the key issues is the process technique for gate dielectric formation because the channel mobility of graphene FET is drastically affected by the gate dielectric interface quality. Formation of high quality gate dielectric on graphene is still a challenging. Dirac voltage, the charge neutral point of the device, also strongly depends on gate dielectrics. Another performance killer in graphene FET is source/drain contact resistance, as the contact resistant between metal and graphene S/D is usually one order of magnitude higher than that between metal and silicon S/D. In this presentation, the key issues on graphene-based FET, including organic-inorganic hybrid gate dielectric formation, controlling of Dirac voltage, reduction of source/drain contact resistance, device structure optimization, graphene gate electrode for improvement of gate dielectric reliability, and CVD graphene transfer process issues are addressed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.343-343
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• 2008

Newly designed structure of a thin ultrasonic rotary motor was proposed. Thin brass plate was used as a cross shaped vibrator and eight ceramic plates were attached on the upper and bottom sides of the brass plate as in Figure 1. The thin type ultrasonic motor has the structure adherent piezoelectric ceramic on the top and bottom surface of the thin elastic body. The direction of polarization is decided so as to occur the elliptical displacement in regular sequence at touch point A, B, C and D of stator contacted with rotor. By applying two electric fields which have 90 degree phase difference on the ceramics, each contact points make rotational displacements as in figure 2. Finite element analysis program ATILA was used to find the optimal size of the stator. As a result of the simulation, elliptical displacements of the tips were obtained at off-resonance frequencies. The maximum displacements of the contact tips were obtained at the length of 16[mm], width of 6[mm] and thickness of 0.4[mm]. Changes of the resonance frequencies were inversely proportional to the length of ceramic and proportional to the width of ceramic. Elliptical motions of the contact tips. of the stator were consistently obtained at off resonance frequencies. From a prototype motor, speed of 600[rpm] was obtained at 20[Vrms].

• Corrosion Science and Technology
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• v.21 no.3
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• pp.200-208
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• 2022

Aluminum alloy is used by adding various elements according to the needs of the industry. Aluminum alloys such as 5052 and 6061 are known to possess excellent corrosion resistance by adding Mg. Despite their excellent physical properties, corrosion can occur. To solve this problem, an anodization technique generally can improve corrosion resistance by forming an oxide structure with maximized hydrophobic properties through coatings. In this study, the anodizing technique was used to improve the hydrophobicity of aluminum 5052 and 6061 by creating porous nanostructures on top of the surface. An oxide film was formed by applying anodizing voltages of 20, 40, 60, 80, and 100 V to aluminum alloys followed by immersion in 0.1 M phosphoric acid for 30 minutes to expand oxide pores. Contact angle and corrosion characteristics were different according to the structure after anodization. For the 5052 aluminum, the corrosion potential was improved from -363 mV to -154 mV as the contact angle increased from 116° to 136°. For the 6061 aluminum, the corrosion potential improved from -399 mV to -124 mV when the contact angle increased from 116° to 134°.

• Journal of radiological science and technology
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• v.45 no.3
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• pp.205-211
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• 2022

This study aimed to provide basic data for 3D printing in the medical health field by developing upper wear fixation device (UWFD), an auxiliary device for shortening chest AP examination time on emergency room beds and non-contact with patients. The standard of hooks was modeled according to the bed frame using the Autodesk Fusion 360. It was printed with Form2 (Formlabs, Somerville, MA, USA), as SLA (stereo lithography apparatus) method, and was washed and hardened using Form Wash and Form Cure. The completed UWFD conducted an online survey on 4 items of stability, convenience, availability, preference and general characteristics. The total stability average was 3.93±0.80, the total convenience average was 3.93±0.68, the total availability average was 4.01±0.89, and the total preference average was 3.80±1.08. This study was significant in suggesting improvements in the general X-ray examination process in the emergency room by designing and making aids to easily fixing the patient's top to the frame of the emergency bed while meeting promptness and non-contact with the patient.

• Advances in nano research
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• v.13 no.4
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• pp.369-378
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• 2022

Dynamic study of concrete plates under impact load is presented in this article. The main objective of this work is presenting a mathematical model for the concrete plates under the impact load. The concrete plate is reinforced by carbon nanoparticles which the effective material proprieties are obtained by mixture's rule. Impacts are assumed to occur normally over the top layer of the plate and the interaction between the impactor and the structure is simulated using a new equivalent three-degree-of-freedom (TDOF) spring-mass-damper (SMD) model. The structure is assumed viscoelastic based on Kelvin-Voigt model. Based on the classical plate theory (CPT), energy method and Hamilton's principle, the motion equations are derived. Applying DQM, the dynamic deflection and contact force of the structure are calculated numerically so that the effects of mass, velocity and height of the impactor, volume percent of nanoparticles, structural damping and geometrical parameters of structure are shown on the dynamic deflection and contact force. Results show that considering structural damping leads to lower dynamic deflection and contact force. In addition, increasing the volume percent of nanoparticles yields to decreases in the deflection.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.651-653
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• 2008

In this paper, we report electrical properties of OTFTs by using ink-jet printing with polyvinylphenol (PVP) for gate insulator and bis(triisopropylsilylenthynyl) pentacene (TIPS pentacene) for semiconductor. OTFTs produced the excellent performance with the mobility of $1.27\;cm^2/V.s$ for top contact structure(TCS) and inverter consisting of two OTFTs exhibited the gain of 6.75.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.271-272
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• 2007

Displacement current $(I_{dis})$ and drain-to-source current $(I_{DS})$ are evaluated using the simultaneous measurements of source $(I_S)$ and drain $(I_D)$ currents during the application of a constant drain voltage and a triangular-wave gate voltage $(V_{GS})$ to top-contact pentacene thin-film transistors.