• Journal of Sensor Science and Technology
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• 제32권6호
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• pp.425-431
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• 2023

An asymmetric metal-semiconductor-metal Al_0.24Ga_0.76N ultraviolet (UV) sensor was fabricated, and the effects of local Joule heating were investigated. After dielectric breakdown, the current density under a reverse bias of 2.0 V was 1.1×10^-9 A/cm², significantly lower than 1.2×10^-8 A/cm² before dielectric breakdown; moreover, the Schottky behavior of the Ti/Al/Ni/Au electrode changed to ohmic behavior under forward bias. The UV-to-visible rejection ratio (UVRR) under a reverse bias of 7.0 V before dielectric breakdown was 87; however, this UVRR significantly increased to 578, in addition to providing highly reliable responsivity. Transmission electron microscopy revealed interdiffusion between adjacent layers, with nitrogen vacancies possibly formed owing to local Joule heating at the AlGaN/Ti/Al/Ni/Au interfaces. X-ray photoelectron microscopy results revealed decreases in the peak intensities of the O 1s binding energies associated with the Ga-O bond and OH-, which act as electron-trapping states on the AlGaN surface. The reduction in dark current owing to the proposed local heating method is expected to increase the sensing performance of UV optoelectronic integrated devices, such as active-pixel UV image sensors.

• Journal of the Korean Ceramic Society
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• 제55권1호
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• pp.55-60
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• 2018

In this study, quantum dots composed of $Mn^{2+}$ doped ZnS core and ZnS shell were synthesized using MPA precursor at room temperature. The ZnS: Mn/ZnS quantum dots were prepared by varying the content of MPA in the synthesis of ZnS shells. XRD, Photo-Luminescence (PL), XPS and TEM were used to characterize the properties of the ZnS: Mn/ZnS quantum dots. As a result of PL measurement using UV excitation light at 365 nm, the PL intensity was found to greatly increase when MPA was added at 15 ml, compared to the case with no MPA; the PL peaks shifted from 603 nm to 598 nm. A UV sensor was fabricated by using a sputtering process to form a Pt pattern and placing a QD on the Pt pattern. To verify the characteristics of the sensor, we measured the electrical properties via irradiation with UV, Red, Green, and Blue light. As a result, there were no reactions for the R, G, and B light, but an energy of 3.39 eV was produced with UV light irradiation. For the sensor using ZnS: Mn/ZnS quantum dots, the maximum current (A) value decreased from $4.00{\times}10^{-11}$ A to $2.62{\times}10^{-12}$ A with increasing of the MPA content. As the MPA content increases, the PL intensity improves but the electrical current value dropped because of the electron confinement effect of the core-shell.

• Proceedings of the KIEE Conference
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• 대한전기학회 2008년도 추계학술대회 논문집 전기설비전문위원
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• pp.76-77
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• 2008

The purposes of this paper ensure for the economical efficiency, accuracy, and good applications in domestic site set up the power installations. For the efficient conduct of these purposes, there are measured the partial discharge(PD) used by current probe and compared with detected signal of UV sensor. As the results, PD generated about 35% of breakdown voltage in polymer insulator. UV signal due to high voltage in polymer insulator is detected from about 1.7mV at 30kV to about 3mV at 70kV. Signal detected by ultra-sonic is increased at about 75% of breakdown voltage abruptly. It appears that error range is increased in boundary. UV sensor is needed must use from the practical and economical points of view.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.638-638
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• 2013

ZnO는 넓은 밴드갭(3.37 eV)를 가지기 때문에 UV detector로 유용하게 쓰일 수 있다. 본 연구에서는 Graphene 위에 ZnO nanorod를 hydrothermal 방법을 사용하여 성장한 후 Graphene 위에 전극을 형성한 후 UV 센서를 제작하였다. Si의 기판위에 SiO2의 막을 증착을 하고 그 위에 Graphene을 전도시킨다. Graphene위에 ZnO nanorod의 성장을 위해서 ZnO seed layer를 sputtering 방법으로 얇게 증착을 시킨다. ZnO nanorod의 성장은 hydrothermal의 방법으로 Zinc nitrate hexahydrate와 암모니아를 수용액에 넣은 후 $80^{\circ}C$에서 성장하였다. Graphene 위에 ZnO가 없는 부분에 전극을 형성하여 UV의 세기에 따른 IV 전기적 특성의 변화를 관측한다.

• Journal of the Korean institute of surface engineering
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• 제47권6호
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• pp.297-302
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• 2014

ZnS nanowires were synthesized in order to investigate $NO_2$ gas sensing properties. They were grown on the sapphire substrate using ZnS powders. SEM (scanning electron microscopy) showed the diameter and length of the ZnS nanowires were approximately in the range of 50 - 100 nm and a few $10s\;{\mu}m$, respectively. They were also found to be composed of Wurtzite- structured single crystals from TEM (transmission electron microscopy) analysis. $NO_2$ gas sensing performance of the ZnS nanowire was measured with electrical resistance changes caused by $NO_2$ gas with a concentration of 1-5ppm. The sensor was UV treated with an intensity of $1.2mW/cm^2$ to facilitate charge carrier transfer. The responses of the ZnS nanowires to the $NO_2$ gas at room temperature, treated with UV of two different wavelengths of 365 nm and 254 nm, are measured to be 124.53 - 206.87 % and 233.97 - 554.83%, respectively. In the current work, the effect of UV treatment on the gas sensing performance of the ZnS nanowires was studied. And the underlying mechanism for the electrical resistance changes of the ZnS nanowires by $NO_2$ gas was also discussed.

• Transactions on Semiconductor Engineering
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• 제1권1호
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• pp.9-13
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• 2023

An AlGaN/GaN heterojunction-based hydrogen sensor with SnO₂ nanoparticles/Pd catalyst layer was fabricated for room-temperature hydrogen detection. The fabricated sensor exhibited unstable drift in standby current when it was operated at room temperature. The instability in the sensing signal was dramatically improved when the sensor was operated under UV illumination.

• Proceedings of the KSR Conference
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2043-2048
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• 2011

According to the statistical report from National Emergency Management Agency (NEMA) in Korea, the accident rate of closed switchboards in power systems occupies over 40%. In this paper, an integrated sensor module for monitoring the condition of closed switchboards is described. The sensor module monitors electro-magnetic (EM) wave, ultra-violet (UV) ray, heat and smoke generated by electrical discharges or insulation breakdown. The effective detection ranges were decided from experiment results; 100 kHz~10 MHz for EM wave, 220 nm~395 nm for UV ray and 0~$150^{\circ}C$ for heat, respectively. The prototype sensor module includes all functions above-mentioned in one device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집
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• pp.31-35
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• 2004

We propose driving method of Ultraviolet sensor for fire alarms using pulse width modulation that used to fire detector with sensor of private-use detectable light energy as ultraviolet in energy of electromagnetic-wave type radiate from flame, when combustible burn with contain carbon,. Ultraviolet sensor is UV Tron using gas multiplication effect to current discharge and photoelectric effect of metal. To have high sensibility and to gain proper output voltage, it has high responsive performance. This research designed driving circuit with UV sensors and proposed method of false alarm reduced to resemble fire. the result propers the prevention and extinction of fire technique degree, certificated operation of detector.

• Journal of Photoscience
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• 제6권1호
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• pp.5-6
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• 1999

Solar ultraviolet-B (UV-B) irradiances incident on a horizantal surface at Taegu of Korea during 1995-1998 were calculated with 5 min averges of measuremets taken every 30 seconds by a broadband UV-B sensor. The maximum and minimum of monthly averages of daily UV-B dose were 15.89 KJ m-2 day-1 in April and 3.91KJm-2 day-1 on May 22, 1998 and 1.230W m-2 at 12 : 45, July 13, 1998, respectively. Increasing trend in annual maximum of instantaneous UV-B radiation was averaged to 12.0% per year during 1995-1998 of observation period.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제30권8호
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• pp.508-513
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• 2017

Ultraviolet (UV) photodetectors are used in various industries and fields of research, including optical communication, flame sensing, missile plume detection, astronomical studies, biological sensors, and environmental research. However, general UV detectors that employ Schottky junction diodes and p-n junctions have high fabrication cost and low quantum efficiency. In this study, we investigated the characteristics of materials used to manufacture UV photodetectors in a low-cost solution process that requires easy fabrication of flexible substrates. We fabricated p-type NiO and n-type ZnO substrates with wide band gap by the sol-gel method and compared the characteristics of substrates prepared under different spin-coating and heat-treatment conditions.