• Current Optics and Photonics
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• v.5 no.1
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• pp.1-7
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• 2021

For higher sensitivity in ultraviolet (UV) and even vacuum ultraviolet (VUV) detection of silicon-based sensors, a sandwich-structured film sensor based on Ag Localized Surface Plasmon Resonance (LSPR) was designed and fabricated. This film sensor was composed of a Ag nanoparticles (NPs) layer, SiO2 buffer and fluorescence layer by physical vapour deposition and thermal annealing. By tuning the annealing temperature and adding the SiO2 layer, the resonance absorption wavelength of Ag NPs matched with the emission wavelength of the fluorescence layer. Due to the strong plasmon resonance coupling and electromagnetic field formed on the surface of Ag NPs, the radiative recombination rate of the luminescent materials and the number of fluorescent molecules in the excited state increased. Therefore, the fluorescent emission intensity of the sandwich-structured film sensor was 1.10-1.58 times at 120-200 nm and 2.17-2.93 times at 240-360 nm that of the single-layer film sensor. A feasible method is provided for improving the detection performance of UV and VUV detectors.

• Korean Journal of Materials Research
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• v.32 no.9
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• pp.396-402
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• 2022

In this study, surface roughness and interfacial defect characteristics were analyzed after forming a high-k oxide film on the surface of a prime wafer and a test wafer, to study the possibility of improving the quality of the test wafer. As a result of checking the roughness, the deviation in the test after raising the oxide film was 0.1 nm, which was twice as large as that of the Prime. As a result of current-voltage analysis, Prime after PMA was 1.07 × 10 A/cm² and Test was 5.61 × 10 A/cm², which was about 5 times lower than Prime. As a result of analyzing the defects inside the oxide film using the capacitance-voltage characteristic, before PMA Prime showed a higher electrical defect of 0.85 × 10¹² cm^-2 in slow state density and 0.41 × 10¹³ cm^-2 in fixed oxide charge. However, after PMA, it was confirmed that Prime had a lower defect of 4.79 × 10¹¹ cm^-2 in slow state density and 1.33 × 10¹² cm^-2 in fixed oxide charge. The above results confirm the difference in surface roughness and defects between the Test and Prime wafer.

• Korean Journal of Materials Research
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• v.34 no.4
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• pp.202-207
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• 2024

In this study, we undertook detailed experiments to increase hydrogen production efficiency by optimizing the thickness of titanium dioxide (TiO₂) thin films. TiO₂ films were deposited on p-type silicon (Si) wafers using atomic layer deposition (ALD) technology. The main goal was to identify the optimal thickness of TiO₂ film that would maximize hydrogen production efficiency while maintaining stable operating conditions. The photoelectrochemical (PEC) properties of the TiO₂ films of different thicknesses were evaluated using open circuit potential (OCP) and linear sweep voltammetry (LSV) analysis. These techniques play a pivotal role in evaluating the electrochemical behavior and photoactivity of semiconductor materials in PEC systems. Our results showed photovoltage tended to improve with increasing thickness of TiO₂ deposition. However, this improvement was observed to plateau and eventually decline when the thickness exceeded 1.5 nm, showing a correlation between charge transfer efficiency and tunneling. On the other hand, LSV analysis showed bare Si had the greatest efficiency, and that the deposition of TiO₂ caused a positive change in the formation of photovoltage, but was not optimal. We show that oxide tunneling-capable TiO₂ film thicknesses of 1~2 nm have the potential to improve the efficiency of PEC hydrogen production systems. This study not only reveals the complex relationship between film thickness and PEC performance, but also enabled greater efficiency and set a benchmark for future research aimed at developing sustainable hydrogen production technologies.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.745-752
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• 2024

A method for gamma/neutron event classification based on frequency-domain analysis for mixed radiation environments is proposed. In contrast to the traditional charge comparison method for pulse-shape discrimination, which requires baseline removal and pulse alignment, our method does not need any preprocessing of the digitized data, apart from removing saturated traces in sporadic pile-up scenarios. It also features the identification of neutron events in the detector's full energy range with a single device, from thermal neutrons to fast neutrons, including low-energy pulses, and still provides a superior figure-of-merit for classification. The proposed frequency-domain analysis consists of computing the fast Fourier transform of a triggered trace and integrating it through a simplified version of the transform magnitude components that distinguish the neutron features from those of the gamma photons. Owing to this simplification, the proposed method may be easily ported to a real-time embedded deployment based on Field-Programmable Gate Arrays or Digital Signal Processors. We target an off-the-shelf detector based on a small CLYC (Cs2LiYCl6:Ce) crystal coupled to a silicon photomultiplier with an integrated bias and preamplifier, aiming at lightweight embedded mixed radiation monitors and dosimeter applications.

• Journal of the Optical Society of Korea
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• v.7 no.4
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• pp.230-233
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• 2003

This study describes the conceptual design of a soft x-ray microscope system based on a laserbased source for biomedical application with high resolution (${\leq}$50nm). The laboratory scale soft x-ray microscope consists of high power laser plasma x-ray source and grazing incidence mirrors with high reflectivity. The laser plasma source used for developing this system employs Q-switched Nd-YAG pulsed laser. The laser beam is focused on a tantalum (Ta) target. The Wolter type I mirror was used as condenser optics for sample illumination and as objective mirror for focusing on a detector. The fabrication of the Wolter type I mirror was direct internal cutting using ultraprecision DTM. A hydrated biological specimen was put between the two silicon wafers, the center of which was $Si_3N_4$ windows of 100㎚ thickness. The main issues in the future development work are to make a stable, reliable and reproducible x-ray microscope system.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2482-2487
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• 2007

Numerical simulations are conducted for the analysis of a thermal mass air flow sensor with periodic heating pulses on silicon-nitride ($Si_3N_4$) thin membrane structure. This study aims to find the locations of temperature sensors on the thin membrane and the heating pulse conditions, that the higher sensitivity can be achieved, for the development of a MEMS fabricated mass air flow sensor which is driven in periodic heating pulse. The simulations, thus, focus on the membrane temperature profile according to variation of the flow velocity, heating duration time and imposed power. The flow velocity of the simulations is ranging from 3 m/s to 35 m/s, heating duration time from 1 ms to 3 ms and imposed power from 50 mW to 90 mW. The corresponding Reynolds numbers vary from 1000 to 10000.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1576-1578
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• 2004

The alumina membrane with nano sized pore was prepared from aluminum by anodic oxidation to apply for storage equipment, gas sensor and stamper. The pore size and cell size of the pores are controlled by anodic oxidation voltage. The alumina thickness was controlled by etching process using 0.2M $H_3PO_4$. The thickness of alumina on Si wafer was very accurately controlled by anodic oxidation time. Nickel with nano-sized grain was electroplated on the Au layer on silicon wafer. The fabricated pores on alumina membrane was the thickness of $7{\sim}10{\mu}m$ with straight nano-sized pore of 307${\sim}$120nm. The alumina by the etching process shows smooth surface. The size of Ni grain was 130nm and 250nm for 10mA/$cm^2$and 20mA/$cm^2$of electroplating currents, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.869-871
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• 2012

In this paper, we make silicon photodiodes for the detection of pulsed radiation that affects electronics devices and study the output characteristics of photodiodes using circuit design. We conducted the simulation for pulse sensing circuit and experimented the photodiode output characteristics using a high luminance light emitting diode. The results can be used for the design of the input sensor that is trigger of additional module for protecting a electoronics circuit from high energy pulse radiation.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.509-512
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• 2004

This paper proposed a new solid State Relay(SSR) structure that can replace the conventional SSR as a power IC. The photodiode arrays, the main part of this structure, were designed and integrated in the same power It chip with the output parts, LDMOSFET and BJT, on a SOI substrate. The fabrication of this input part shared the same output LDMOSFET fabrication processs, except the additional deposition of Silicon nitride($Si_3N_4$) for the photo-detection part. According to LED illumination intensites and photo detecting areas, we could obtain voltage of 0.49V ${\~}$0.52V and current of 5.5uA ${\~}$ 108uA respectively from the fabricated unit photodiode. The maximum value of the voltage and the current we could obtain from the photodiode array were 3.58V and 24.4uA respectively, and the voltage was enough to operate the output LDMOSFET

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.295-295
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• 2016

Recently, TCO films with low carrier concentration, high mobility and high work function are proposed beneficial as front electrode in HIT solar cell due to free-carrier absorption in NIR wavelength region and low Schottky barrier height in the front TCO/a-Si:H(p) interface. We report high transmittance and work function zirconium-doped indium tin oxide (ITO:Zr) films with various plasma (Ar/O2 and Ar) conditions. The role of (Ar/O2) plasma was to enhance the work function of the ITO:Zr films whereas the pure Ar plasma based ITO:Zr showed good electrical properties. The RF magnetron sputtered ITO:Zr films with low resistivity and high transmittance were employed as front electrode in HIT solar cells, yield the best performance of 18.15% with an open-circuit voltage of 710 eV and current density of 34.63 mA/cm2. The high work function ITO:Zr films can be used to modify the front barrier height of HIT solar cell.