• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.398-398
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• 2011

CIGS/CdS/i-ZnO의 hetero junction으로 구성된 CIGS 태양전지는 적색광 광전류-전압 곡선특성이 백색광 곡선에 비해 크게 왜곡된다. 이는 CdS층의 광흡수에 따른 광전도도의 변화가 pn junction의 에너지밴드구조를 변화시키기 때문으로 알려져 있고, 그 정도는 CdS의 deep level acceptor 트랩의 존재와 같은 CdS 박막의 특성과 밀접한 관련이 있는 것으로 판단된다. 따라서, 백색광과 적색광에 의한 광전류-전압 특성의 차이로부터 CdS 및 CdS/CIGS 계면의 전기, 전자적특성을 평가할 수 있을 것으로 기대된다. 특히, 백색광에 비해 적색광에서는 온도가 내려갈수록 광전류-전압의 왜곡이 훨씬 심해지는 것을 확인하였다. 이러한 왜곡현상은 광세기에 의한 영향은 거의 없고, 백색광과 적색광의 광스펙트럼의 변화에 의해 나타났으며, CdS의 blue photon 흡수 여부와 관련이 있는 것으로 판단된다. CIGS 태양전지는 CdS 증착을 전후로 한 열처리가 광전압을 향상시키는 것으로 알려져 있으므로, 본 연구에서는 그러한 열처리에 의한 CdS/CIGS 계면의 특성 변화를 백색광, 적색광에 의한 저온 광전류-전압 특성 측정을 통하여 분석하였다. 열처리는 CdS를 증착한 후 $100^{\circ}C$ 부터 $250^{\circ}C$ 까지 $50^{\circ}C$ 간격으로 진행하였고, 전류-전압 특성은 100K 부터 300K 까지 10K 간격으로 측정하였다. 백색광, 적색광 저온 광전류-전압 특성의 변화를 열처리에 다른 태양전지 셀효율과 비교 분석하였다.

• 지구물리와물리탐사
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• 제11권3호
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• pp.167-176
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• 2008

태평양 해양 지각판과 인도-호주 대륙 지각판간 섭입작용에 의해 형성된 남태평양 라우분지는 활동성 후열도분지로서 해저열수광상이 부존할 가능성이 매우 높은 지역이다. 한국해양연구원은 라우분지를 대상으로 다중음향측심장비(EM120)을 이용하여 정밀지형조사를 실시하여 열수활동이 활발할 것으로 예측되는 해저 지각 확장축 주변지역 (FRSC)과 해저화산 지역(MTJ)을 선별하였다. 또한, 표층 및 심해견인 자력탐사결과를 토대로 저 자기이상 현상을 나타내는 열수광체 지역을 선정하였다. 표층 및 심해 견인 자력탐사 결과 해령에서 주로 나타나는 Central Anomaly Magnetization High(CAMH)가 FRSC-2 지역에서 관측되었으며, MTJ-1 지역에서는 열수분출작용으로 추정되는 저자화이상이 발견되었다. CTD 시스템을 이용하여 열수 플룸 추적자인 투명도, 수소이온(pH), 미생물생체량(ATP), 메탄$(CH_4)$농도를 실시간으로 측정한 결과 FRSC-2와 MTJ-1 지역은 현재 매우 활발한 화산 활동이 진행되고 있음을 알 수 있었다. 이 지역에서 채취한 열수분출공과 기반암 시료는 이 지역에서 열수활동이 진행되었거나 진행되고 있으며, 실제로 열수 광체가 부존하고 있음을 확인할 수 있었다. 첨단 해저면 영상장비를 사용하지 않고도, 전통적인 해양 지구물리탐사 방법이 해저열수광상의 탐지에 비용 효과적인 탐사방법임을 알 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.454-454
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• 2014

Silicon microwire array is one of the promising platforms as a means for developing highly efficient solar cells thanks to the enhanced light trapping efficiency. Among the various fabrication methods of microstructures, deep reactive ion etching (DRIE) process has been extensively used in fabrication of high aspect ratio microwire arrays. In this presentation, we show precisely controlled Si microwire arrays by tuning the DRIE process conditions. A periodic microdisk arrays were patterned on 4-inch Si wafer (p-type, $1{\sim}10{\Omega}cm$) using photolithography. After developing the pattern, 150-nm-thick Al was deposited and lifted-off to leave Al microdisk arrays on the starting Si wafer. Periodic Al microdisk arrays (diameter of $2{\mu}m$ and periodic distance of $2{\mu}m$) were used as an etch mask. A DRIE process (Tegal 200) is used for anisotropic deep silicon etching at room temperature. During the process, $SF_6$ and $C_4F_8$ gases were used for the etching and surface passivation, respectively. The length and shape of microwire arrays were controlled by etching time and $SF_6/C_4F_8$ ratio. By adjusting $SF_6/C_4F_8$ gas ratio, the shape of Si microwire can be controlled, resulting in the formation of tapered or vertical microwires. After DRIE process, the residual polymer and etching damage on the surface of the microwires were removed using piranha solution ($H_2SO_4:H_2O_2=4:1$) followed by thermal oxidation ($900^{\circ}C$, 40 min). The oxide layer formed through the thermal oxidation was etched by diluted hydrofluoric acid (1 wt% HF). The surface morphology of a Si microwire arrays was characterized by field-emission scanning electron microscopy (FE-SEM, Hitachi S-4800). Optical reflection measurements were performed over 300~1100 nm wavelengths using a UV-Vis/NIR spectrophotometer (Cary 5000, Agilent) in which a 60 mm integrating sphere (Labsphere) is equipped to account for total light (diffuse and specular) reflected from the samples. The total reflection by the microwire arrays sample was reduced from 20 % to 10 % of the incident light over the visible region when the length of the microwire was increased from $10{\mu}m$ to $30{\mu}m$.

• 자원환경지질
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• 제41권1호
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• pp.81-92
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• 2008

Fonualei Rift and Spreading Center(FRSC)와 Mangatolu Triple Junction(MTJ) 칼데라는 활동성 후호분지인 라우(Lau)분지 북동쪽에 위치하고 있다. FRSC에서는 심해 견인 및 표층 자력탐사가 수행되었으며, 심해 견인 자력탐사에서 나타나는 해저 지형과 자력계 고도 사이의 거리 변화 영향을 보정하기 위해 Guspi의 상향연속법을 이용하여 동일한 고도에서 측정한 값으로 변환하였다. Parker and Huestis의 역산 알고리즘을 이용하여 해양지각의 자화를 계산하였고, 이로부터 심해저 열수 분출구 탐사와 해저지각 구조를 파악하고자 하였다. FRSC의 심해 견인 자력탐사 결과 해령에서 주로 나타나는 최대 4.5 A/m의 Central Anomaly Magnetization High(CAMH)가 관측되었으며, 남남서-북북동으로 추정되는 해령의 방향은 라우분지 내 주요 확장축의 방향과 일치하는 경향을 보인다. 또한 FRSC에서는 열수 분출구로 의심되는 - 4.0 A/m의 저자화이상이 발견되었다. MTJ 칼데라$(174^{\circ}00'W\;15^{\circ}20'S)$에서는 표층 자력탐사만이 수행되었고, 남남서-북북동 방향으로 함몰된 화륜과 중앙에서 나타나는 CAMH를 통해 칼데라 중심에 활동성 확장축이 존재하는 것으로 판단된다.

• 대한전자공학회논문지SD
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• 제39권5호
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• pp.1-7
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• 2002

Deep sub-micron bulk CMOS circuits require gate electrode materials such as metal silicide and titanium silicide for gate oxides. Many authors have conducted research to improve the quality of the sub-micron gate oxide. However, few have reported on the electrical quality and reliability of an ultra-thin gate. In this paper, we will recommend a novel shallow trench isolation structure and a two-step TiS $i_2$ formation process to improve the corner metal oxide semiconductor field-effect transistor (MOSFET) for sub-0.1${\mu}{\textrm}{m}$ VLSI devices. Differently from using normal LOCOS technology, deep sub-micron CMOS devices using the novel shallow trench isolation (STI) technology have unique "inverse narrow-channel effects" when the channel width of the device is scaled down. The titanium silicide process has problems because fluorine contamination caused by the gate sidewall etching inhibits the silicide reaction and accelerates agglomeration. To resolve these Problems, we developed a novel two-step deposited silicide process. The key point of this process is the deposition and subsequent removal of titanium before the titanium silicide process. It was found by using focused ion beam transmission electron microscopy that the STI structure improved the narrow channel effect and reduced the junction leakage current and threshold voltage at the edge of the channel. In terms of transistor characteristics, we also obtained a low gate voltage variation and a low trap density, saturation current, some more to be large transconductance at the channel for sub-0.1${\mu}{\textrm}{m}$ VLSI devices.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 하계학술발표회
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• pp.28-29
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• 2000

Optical power splitters and/or couplers are important components for optical signal distribution between channels both in wavelength division multiplexing(WDM) systems and photonic integrated circuits(PICs). Since polarization is usually not known after propagation in an optical fiber, passive WDM components have to be polarization insensitivity, Compared to alternatives such as directional couplers or Y-junction splitters, splitters based on multimode interference(MMI) have found a growing interest in recent yens because of their desirable characteristics, such as compact size, low excess loss, wide bandwidth, polarization independence, and relaxed fabrication tolerances$^{(1)}$ . These devices have been fabricated in polymers, silica, or III-V semiconductor materials. A1 $\times$ 4 MMI power splitter on InP materials that were suitable for application in the 1.55-${\mu}{\textrm}{m}$ region$^{(2)}$ . However, the fabrication process of the structure is too complicated and the photolithography tolerance is very tight. Also, a 1 $\times$ 16 InGaAsP/InP MMI power splitter with an excess loss of 2.2dB and a splitting ratio of 1.5dB was demonstrated by using deep etching$^{(3)}$ . The deep etching of the sidewalls through the entire guide layer of the slab waveguide resulted in a number of drawbacks$^{(4)}$ . (omitted)

• Transactions on Electrical and Electronic Materials
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• 제5권5호
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• pp.169-172
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• 2004

Deep sub-micron device required to get the superior ultra thin gate oxide characteristics. In this research, I will recommend a novel shallow trench isolation structure(STI) for thin gate oxide and a $N_2$O gate oxide 30 $\AA$ by NO ambient process. The local oxidation of silicon(LOCOS) isolation has been replaced by the shallow trench isolation which has less encroachment into the active device area. Also for $N_2$O gate oxide 30 $\AA$, ultra thin gate oxide 30 $\AA$ was formed by using the $N_2$O gate oxide formation method on STI structure and LOCOS structure. For the metal electrode and junction, TiSi$_2$ process was performed by RTP annealing at 850 $^{\circ}C$ for 29 sec. In the viewpoints of the physical characteristics of MOS capacitor, STI structure was confirmed by SEM. STI structure was expected to minimize the oxide loss at the channel edge. Also, STI structure is considered to decrease the threshold voltage, result in a lower Ti/TiN resistance( Ω /cont.) and higher capacitance-gate voltage(C- V) that made the STI structure more effective. In terms of the TDDB(sec) characteristics, the STI structure showed the stable value of 25 % ～ 90 % more than 55 sec. In brief, analysis of the ultra thin gate oxide 30 $\AA$ proved that STI isolation structure and salicidation process presented in this study. I could achieve improved electrical characteristics and reliability for deep submicron devices with 30 $\AA$ $N_2$O gate oxide.

• 대한전자공학회논문지SD
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• 제49권5호
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• pp.16-21
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• 2012

본 논문에서는 CMOS 기반의 BJT 제작에 있어서 일반적인 BJT 구조에 비해 정합특성이 우수한 새로운 BJT 구조를 제안하고, 특성을 비교 분석하였다. 새로운 정합 구조가 기존의 정합 구조에 비해 콜렉터 전류 밀도 $J_C$는 0.361% 감소하였고, 전류이득 ${\beta}$는 0.166% 증가하여 큰 차이가 보이지 않았지만, 소자 면적이 10% 감소했으며, 콜렉터 전류($A_{Ic}$)와 전류이득($A_{\beta}$)의 정합 특성이 각각 45.74%, 38.73% 향상되었다. 이와 같이 정합특성이 개선된 주 이유는 쌍으로 형성된 BJT 소자들의 에미터 간의 거리가 감소한 것이라고 생각되며, deep n-well 저항의 표준편차 값이 다른 저항들에 비해 큰 것으로부터 간접적으로 증명이 된다고 여겨진다.

• Journal of Chest Surgery
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• 제55권3호
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• pp.233-238
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• 2022

Background: This study investigated the distribution of valve incompetence in patients with chronic venous disease (CVD) and its correlation with the clinical category of the clinical, etiological, anatomical, and pathophysiological (CEAP) classification. Methods: In total, 1,386 limbs with clinically suspected CVD were categorized according to the CEAP classification and consecutively underwent duplex ultrasonography between April 2017 and December 2020. Results: There were 362 limbs in male patients and 1,024 limbs in female patients. The limbs were classified as C0s-C1 (608 limbs, 43.8%), C2 (727 limbs, 52.5%), or C3-C6 (51 limbs, 3.7%). The prevalence of saphenous vein incompetence in CEAP C0s-C1 limbs was 43.6%. The saphenofemoral junction (SFJ) was competent in 37% of CEAP C2-C6 limbs. The CEAP C3-C6 category was not correlated with reflux patterns of the saphenous vein system (Cramer's V=0.07), incompetent SFJ (Cramer's V=0.07), deep vein reflux (Cramer's V=0.03), or the distribution of incompetent segments in the great saphenous vein (GSV) (Cramer's V=0.11). Conclusion: Duplex ultrasonography is necessary to formulate a proper treatment plan for limbs categorized as CEAP C0s-C1. The SFJ was competent in more than one-third of CEAP C2-C6 limbs with GSV reflux; as such, flush ligation of the GSV may be unnecessary in these patients. The CEAP C3-C6 category showed no correlations with reflux patterns of the saphenous vein system, SFJ reflux, deep vein reflux, or the distribution of incompetent segments in the GSV.

• Current Photovoltaic Research
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• 제4권1호
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• pp.12-15
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• 2016

Screen printing technique followed by firing has commonly been used as metallization for both laboratory and industrial based solar cells. In the solar cell industry, the firing process is usually conducted in a belt furnace and needs to be optimized for fabricating high efficiency solar cells. The printed-Al layer on the silicon is rapidly heated at over $800^{\circ}C$ which forms a layer of back surface field (BSF) between Si-Al interfaces. The BSF layer forms $p-p^+$ structure on the rear side of cells and lower rear surface recombination velocity (SRV). To have low SRV, deep $p^+$ layer and uniform junction formation are required. In this experiment, firing process was carried out by using conventional tube furnace with $N_2$ gas atmosphere to optimize $V_{oc}$ of laboratory cells. To measure the thickness of BSF layer, selective etching was conducted by using a solution composed of hydrogen fluoride, nitric acid and acetic acid. The $V_{oc}$ and pseudo efficiency were measured by Suns-$V_{oc}$ to compare cell properties with varied firing condition.