• 한국진공학회지
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• 제13권1호
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• pp.14-21
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• 2004

오늘날 전력소자의 작동에 고주파를 사용하기 때문에 에너지 손실을 줄이기 위해 전력소자의 스위칭 속도를 증가시키는 것은 필수적이다. 본 연구에서는 $p^+- n^-$ 접합 다이오드의 스위칭 속도를 증가시킬 목적으로 minority carrier의 수명을 감소시킬 수 있는 전자조사를 실시하였다. 다이오드의 전기적 성질에 대한 전자조사의 효과를 나타냈다. 스위칭 속도는 효과적으로 증가하였다. 또한 증가될 것으로 예상되는 접합 누설 전류와 전자조사 후 정전압강하는 최적 조건의 에너지와 dose량으로 조사된 $p^+- n^-$접합 다이오드에서는 무시할 수 있는 정도로 나타났다. DLTS와 C-V 분석은 실리콘 기판에서 전자조사로 감소된 결함은 0.284eV와 0.483eV의 에너지 준위를 갖는 donor-like 결함인 것을 보여준다. 본 연구에서의 실험 결과를 고려해 보면, 전자조사는 $p^+- n^-$ 접합 다이오드 전력 소자의 스위칭 속도를 증가시켜 에너지 손실을 감소시킬 수 있는 가장 유용한 기술이라고 결론지을 수 있다.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.390-397
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• 2022

The use of microwaves as the energy source for synthesis and sintering of ceramics offers substantial advantages compared to conventional gas-fired and electric resistance furnaces. Benefits include much shorter processing times and reaching the sintering temperature more quickly, resulting in superior final product quality. Most oxide ceramics poorly interact with microwave irradiation at low temperatures; thus, a more complex setup including a susceptor is needed, which makes the whole process very complicated. This investigation pursued a new approach, which enabled us to use microwave irradiation directly in poorly coupled oxides. In many solid-state electrochemical devices, the support is either metal or can be reduced to metal. Metal powders in the support can act as an internal susceptor and heat the entire cell. Then sufficient interaction of microwave irradiation and ceramic material can occur as the sample temperature increases. This microwave heating and exothermic reaction of oxidation of the support can sinter the ceramic very efficiently without any external susceptor. In this study, yttria stabilized zirconia (YSZ) and a Ni-YSZ cermet support were used as an example. The cermet was used as the support, and a YSZ electrolyte was coated and sintered directly using microwave irradiation without the use of any susceptor. The results were compared to a similar cell prepared using a conventional electric furnace. The leakage test and full cell power measurement results revealed a fully leak-free electrolyte. Scanning electron microscopy and density measurements show that microwave sintered samples have lower open porosity in the electrode support than conventional heat treatment. This technique offers an efficient way to directly use microwave irradiation to sinter thin film ceramics without a susceptor.

• Nuclear Medicine and Molecular Imaging
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• 제40권2호
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• pp.106-112
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• 2006

Tissue hyperplasia is one of the most frequently encountered complications when self-expanding metallic stents are placed in benign non-vascular luminal organ strictures, thus causing restenosis of the lumen. The investigators postulated that ionizing irradiation could be applied to prevent restenosis caused by tissue hyperplasia in non-vascular luminal organs as it reduced coronary or peripheral arterial narrowing successfully. The authors combined $\beta$-irradiation using $^{188}Re-MAG_3$ solution with balloon dilation for animal and clinical studies because this new treatment approach had the advantages such as low penetration depth of $\beta$-ray, self-centering irradiation, and mechanical effect of balloon dilation over using $\gamma$-irradiation with afterloading devices in this article, the concept and mechanism of radioisotope balloon dilation, and animal and clinical studies using radioisotope balloon dilation are reviewed.

• Applied Science and Convergence Technology
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• 제27권2호
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• pp.42-45
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• 2018

Photovoltaic and optoelectronic devices based on hybrid metal halide perovskites ($MAPbX_3$; $MA=CH_3NH_3{^+}$, $X=Cl^-$, $Br^-$, or $I^-$) are rapidly improving in power conversion efficiency. Also, during recent years, perovskite single crystals have emerged as promising materials for high-efficiency photovoltaic and optoelectronic devices because of their low defect density. Here we show that the light soaking effect of mixed halide perovskite ($MAPbBr_{3-x}I_x$) single crystals can be explained using photoluminescence, time-resolved photoluminescence, and Raman scattering measurements. Unlike Br-based single crystal, Br/I mixed single crystal show a strong light soaking effect under laser irradiation condition that was related to the existence of multiple phases.

• ETRI Journal
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• 제27권4호
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• pp.449-452
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• 2005

The electrical characteristics of solid state devices such as the bipolar junction transistor (BJT), metal-oxide semiconductor field-effect transistor (MOSFET), and other active devices are altered by impinging photon radiation and temperature in the space environment. In this paper, the threshold voltage, the breakdown voltage, and the on-resistance for two kinds of MOSFETs (200 V and 100 V of $V_{DSS}$) are tested for ${\gamma}-irradiation$ and compared with the electrical specifications under the pre- and post-irradiation low dose rates of 4.97 and 9.55 rad/s as well as at a maximum total dose of 30 krad. In our experiment, the ${\gamma}-radiation$ facility using a low dose, available at Korea Atomic Energy Research Institute (KAERI), has been applied on two commercially available International Rectifier (IR) products, IRFP250 and IRF540.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2000년도 제1회 신소재 심포지엄(차세대 광소재 심포지엄)
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• pp.77-85
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• 2000

Photosensitive amorphous materials are attractive for the formation of several optical elements by a specific laser beam irradiation. For example the optical fiber gratings prepared by UV laser irradiation are one of the key elements for the recent worldwide progress of wavelength division mutiplexing optical fiber network. This paper reviews the representative studies on the photosensitive materials and the origin of photosensitivity in amorphous oxide materials.

• Journal of Magnetics
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• 제21권2호
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• pp.159-163
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• 2016

Antiferromagnet (AFM)/ferromagnet (FM) bilayer structures are widely used in the magnetic devices of sensor and memory applications, as AFM materials can induce unidirectional anisotropy of the FM material via exchange coupling. The strength of the exchange coupling is known to be sensitive to quality of the interface of the AFM/FM bilayers. In this study, we utilize proton irradiation to modify the interface structures and investigate its effect on the magnetic properties of AFM/FM structures, including the exchange bias and magnetic thermoelectric effect. The magnetic properties of IrMn/CoFeB structures with various IrMn thicknesses are characterized after they are exposed to a proton beam of 3 MeV and $1{\sim}5{\times}10^{14}ions/cm^2$. We observe that the magnetic moment is gradually reduced as the amount of the dose is increased. On the other hand, the exchange bias field and thermoelectric voltage are not significantly affected by proton irradiation. This indicates that proton irradiation has more of an influence on the bulk property of the FM CoFeB layer and less of an effect on the IrMn/CoFeB interface.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2860-2866
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• 2020

Oxide dispersion-strengthened materials W-1wt%Pr₂O₃ and W-1wt%La₂O₃ were synthesized by wet chemical method and spark plasma sintering. The field emission scanning electron microscopy (FE-SEM) analysis, XRD and Vickers microhardness measurements were conducted to characterize the samples. The irradiations were carried out with a 5 keV helium ion beam to fluences up to 5.0 × 10²¹ ions/m² under 600 ℃ using the low-energy ion irradiation system. Transmission electron microscopy (TEM) study was performed to investigate the microstructural evolution in W-1wt%Pr₂O₃ and W-1wt%La₂O₃. At 1.0 × 10²⁰ He⁺/m², the average loops size of the W-1wt%Pr₂O₃ was 4.3 nm, much lower than W-1wt% La₂O₃ of 8.5 nm. However, helium bubbles were not observed throughout in both doped W materials. The effects of pre-irradiation with 1.0 × 10²¹ He⁺/m² on trapping of injected deuterium in doped W was studied by thermal desorption spectrometry (TDS) technique using quadrupole mass spectrometer. Compared with the samples without He⁺ pre-irradiation, deuterium (D) retention of doped W materials increased after He⁺ irradiation, whose retention was unsaturated at the damage level of 1.0 × 10²²D₂⁺/m². The present results implied that irradiation effect of He⁺ ions must be taken into account to evaluate the deuterium retention in fusion material applications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.16-17
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• 2005

Local lifetime control by ion implantation has become an useful tool for production of modern power devices. In this work, punch-through diodes were irradiated with protons for the high speed power diode fabrication. Proton irradiation was executed at the various energy and dose conditions. Characterization of the device was performed by I-V, C-V and Trr measurement. We obtained enhanced reverse recovery time characteristics which was about 45% of original device and about 73% of electron irradiated device. The measurement results showed that proton irradiation was able to effectively reduce minority carrier lifetime.

• 한국전기전자재료학회논문지
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• 제19권3호
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• pp.216-221
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• 2006

Lifetime control technique by proton implantation has become an useful tool for production of modern power devices. In this work, punch-through type diodes were irradiated with protons for the high speed power diode fabrication. Proton irradiation which was capable of controlling carrier's lifetime locally was carried out at the various energy and dose conditions. Characterization of the device was performed by current-voltage, capacitance-voltage and reverse recovery time measurement. We obtained enhanced reverse recovery time characteristics which was about $45\;\%$ of original device reverse recovery time and about $73\;\%$ of electron irradiated device reverse recovery time. The measurement results showed that proton irradiation technique was able to effectively reduce minority carrier lifetime without degrading the other characteristics.