• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.505-508
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• 2006

Self-heating induced device degradation and its width/length (W/L) dimension dependence were studied in p-type polycrystalline silicon (poly-Si) thin film transistors (TFTs). Negative channel conductance was observed under high power region of output curve, which was mainly caused by hole trapping into gate oxide and also by trap state generation by self-heating effect. Self-heating effect became aggravated as W/L ratio was increased, which was understood by the differences in heat dissipation capability. By reducing applied power density normalized to TFT area, self-heating induced degradation could be reduced.

• Journal of Photoscience
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• 제4권1호
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• pp.11-16
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• 1997

We measured, using femtosecond pump-probe experiment, the time evolution of transient absorption in aqueous CdS colloids. The signal rises within the time resolution (= 0.5 ps) of the experiment and decays with two exponential time constants, 4.8 ps and 132 ps. The ultrafast rise of the transient absorption is considered to be for shallowly trapped conduction band electrons after photoexcitation. The amplitude ratio of the two decaying components varies with the pump intensity and the decay times increase in the presence of hole scavengers. Even though a biexponential function fits the decay well, we object hat two independent first order processes (geminate and nongeminate recombinations) are responsible for the decay. A function with an integrated rate equation for second order nongeminate recombination plus a long background fits the decay well. The long background is considered to be for deeply trapped charges at the CdS particle.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.113-116
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• 1996

The drain current of the MOSFET in the off state(i.e., Id when Vgs=0V) is undesired but nevertheless important leakage current device parameter in many digital CMOS IC applications (including DRAMs, SRAMs, dynamic logic circuits, and portable systems). The standby power consumed by devices in the off state have added to the total power consumed by the IC, increasing heat dissipation problems in the chip. In this paper, hot-carrier-induced degra- dation and gate-induced-drain-leakage curr- ent under worse case in P-MOSFET\`s have been studied. First of all, the degradation of gate-induced- drain-leakage current due to electron/hole trapping and surface electric field in off state MOSFET\`s which has appeared as an additional constraint in scaling down p-MOSFET\`s. The GIDL current in p-MOSFET\`s was decreased by hot-electron stressing, because the trapped charge were decreased surface-electric-field. But the GIDL current in n-MOS77T\`s under worse case was increased.

• Applied Science and Convergence Technology
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• 제23권5호
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• pp.254-260
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• 2014

Organic solar cells have attracted extensive attention as a promising approach for cost-effective photovoltaic devices. However, organic solar cell has disadvantage of low power conversion efficiency in comparison with other type of solar cell, due to the recombination ratio of hole and electron is too large in the active layer. Thus we have change the surface structure of PEDOT:PSS layers to improve the current density by colloidal lithography method using various-size of polystyrene sphere. The two types of coating method were applied to fabricate the different pattern shape and height, such as spin coating and drop casting. Using the organic solvent, we easily eliminate the PS sphere and could make the varied pattern shapes by controlling the wet etching time. Also we have measured the electrical properties of patterned PEDOT:PSS film to check whether it is suitable for organic photovoltaics.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권5호
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• pp.519-525
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• 2015

Positive bias stress-induced instability in amorphous indium-gallium-zinc-oxide (a-IGZO) bottom-gate thin-film transistors (TFTs) was investigated under high $V_{GS}$/low $V_{DS}$ and low $V_{GS}$/high $V_{DS}$ stress conditions through incorporating a forward/reverse $V_{GS}$ sweep and a low/high $V_{DS}$ read-out conditions. Our results showed that the electron trapping into the gate insulator dominantly occurs when high $V_{GS}$/low $V_{DS}$ stress is applied. On the other hand, when low $V_{GS}$/high $V_{DS}$ stress is applied, it was found that holes are uniformly trapped into the etch stopper and electrons are locally trapped into the gate insulator simultaneously. During a recovery after the high $V_{GS}$/low $V_{DS}$ stress, the trapped electrons were detrapped from the gate insulator. In the case of recovery after the low $V_{GS}$/high $V_{DS}$ stress, it was observed that the electrons in the gate insulator diffuse to a direction toward the source electrode and the holes were detrapped to out of the etch stopper. Also, we found that the potential profile in the a-IGZO bottom-gate TFT becomes complicatedly modulated during the positive $V_{GS}/V_{DS}$ stress and the recovery causing various threshold voltages and subthreshold swings under various read-out conditions, and this modulation needs to be fully considered in the design of oxide TFT-based active matrix organic light emitting diode display backplane.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.254.2-254.2
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• 2014

The Transmission Fourier Transform Infrared spectroscopy (FTIR) of SiOx charge storage layer with the richest silicon content showed an assignment at peaks around 2000~2300 cm-1. It indicated that the existence of many silicon phases and defect sources in the matrix of the SiOx films. The total hysteresis width is the sum of the flat band voltage shift (${\Delta}VFB$) due to electron and hole charging. At the range voltage sweep of ${\pm}15V$, the ${\Delta}VFB$ values increase of 0.57 V, 1.71 V, and 13.56 V with 1/2, 2/1, and 6/1 samples, respectively. When we increase the gas ratio of SiH4/N2O, a lot of defects appeared in charge storage layer, more electrons and holes are charged and the memory window also increases. The best retention are obtained at sample with the ratio SiH4/N2O=6/1 with 82.31% (3.49V) after 103s and 70.75% after 10 years. The high charge storage in 6/1 device could arise from the large amount of silicon phases and defect sources in the storage material with SiOx material. Therefore, in the programming/erasing (P/E) process, the Si-rich SiOx charge-trapping layer with SiH4/N2O gas flow ratio=6/1 easily grasps electrons and holds them, and hence, increases the P/E speed and the memory window. This is very useful for a trapping layer, especially in the low-voltage operation of non-volatile memory devices.

• Korean Chemical Engineering Research
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• 제47권4호
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• pp.418-423
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• 2009

유기발광다이오드(OLED)에서 정공 주입층(hole injection layer, HIL)으로 사용되는 poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)에 관능성기가 치환된 MWCNT(multi-wall carbon nanotube)를 도입하여 PEDOT:PSS-MWCNT 나노 복합재 박막을 제조하였다. PEDOT:PSS-MWCNT 박막 층은 ITO 유리 위에 스핀 코팅되어 제조하였으며 FT-IR과 UV-Vis 및 SEM을 이용하여 박막의 투과도 및 개질된 MWCNT 함량에 따른 박막의 모폴로지 특성을 관찰하였다. 또한, ITO/PEDOT:PSS-MWCNT/NPD/$Alq_3$/Al 다층 소자를 제조하여 J-V 및 L-V 특성을 고찰하였다. 산 처리에 의해 관능성기가 도입된 MWCNT는 PEDOT:PSS 용액 내에서 분산성이 확인되었으며, 제조된 박막은 우수한 투과도 특성을 보였다. 다층 소자 특성에서 PEDOT:PSS 층에 개질된 MWCNT 도입으로 MWCNT의 함량이 증가함에 따라 다층 소자의 전류 밀도가 증가됨을 확인하였고, 반면에 소자의 휘도는 급격히 감소하는 특성을 보였다. 이것은 MWCNT에 의하여 전하 이동은 수월하게 하였으나 MWCNT가 가지는 정공을 가두는 성질에 의해 정공 이동도가 저하되었기 때문인 것으로 판단된다.

• 비파괴검사학회지
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• 제21권4호
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• pp.398-405
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• 2001

리벳이음은 응력집중 등에 의한 피로균열 발생 가능성이 높은 구조특성을 가지므로 구조물의 안전성 확보를 위하여 비파괴 평가 방법에 의하여 리벳홀 주위 균열에 대한 평가가 요구되고 있다. 유도 초음파의 일종인 Lamb파는 판형상의 구조물의 비파괴 평가에 적합하며, 신경회로망은 비파괴 평가 기술에서 결합의 크기 및 종류 인식에 관하여 가장 효율적인 기법으로 많은 연구자들에 의해 적용되어 왔다. 본 연구에서는 항공기의 스킨재료로 적용되는 A12024-T3판재에 대하여 유도초음파의 일종인 판파를 적용하여 리벳홀 주위 균열 신호를 검출하였으며, 또한 리벳홀 주위 균열의 크기 평가를 위하여 백프로퍼게이션 알고리즘을 적용한 신경회로망을 적용하였다. 이때, 초음파 트랜스듀서와 시험편 사이의 불균일 접촉에 의한 오차를 줄이기 위하여 초음파 파형에서 시간 및 주파수 성분의 특성을 추출하여 신경회로망에 적용하였다. 그리고 이들 판파신호에서 추출한 시간 및 주파수 성분의 특성은 균열 크기 결정에 유용하게 적용될 수 있음을 증명하였다.

• Bulletin of the Korean Chemical Society
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• 제23권9호
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• pp.1229-1258
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• 2002

This paper reports the photochemical reduction of benzil 1 to benzoin 2 and the reduction of 2 to hydrobenzoin 4 in deoxygenated solvents in the presence of triethylamine (TEA) and/or TiO2. Without TEA or TiO2, the photolysis of 1 resulted in very low yield of 2. The presence of TEA or TiO2 increased the rate of disappearance of 1 and the yield of 2, which were further increased considerably by the presence of water. The photoreduction of 1 to 2 proceeds through an electron transfer to 1 from TEA or hole-scavenged excited TiO2 followed by protonation. In the reaction medium of 88 : 7 : 2 : 3 CH3CN/CH3OH/H2O/TEA with 2.5 $㎎/m{\ell}$ of TiO2, the yield of 2 was as high as 85 % at 50 % conversion of 1. The photolysis of 2 in homogeneous media resulted in photo-cleavage to benzoyl and hydroxybenzyl radicals, which are mostly converted to benzaldehyde. The reduction product 4 is formed in low yield through the dimerization of hydroxybenzyl radicals. The addition of TEA increased the conversion rate of 2 and the yield of 4 significantly. This was attributed to the scavenging effect of TEA for benzoyl radical to produce N,N-diethylbenzamide and the photoreduction of benzaldehyde in the presence of TEA. The ratio of $(\pm)$ and meso isomers of 4 obtained from the photochemical reaction is about 1.1. This ratio is the same as that from the photochemical reduction of benzaldehyde in the presence of TEA. In the TiO2-sensitized photochemical reduction of 2, meso-4 was obtained in moderate yield. The reduction of 2 to 4 proceeds through two consecutive electron/proton transfer processes on the surface of the photocatalyst without involvement of ${\alpha}-cleavage$. The radical 11 initially formed from 2 by one electron/proton process can also combine with hydroxy methyl radical, which is generated after hole trapping of excited TiO2 by methanol, to produce 1,2-diphenylpropenone after dehydration reaction.

• 센서학회지
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• 제18권1호
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• pp.48-53
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• 2009

$Eu^{2+}$-doped ${SrAl_2}{O_4}$ and $Eu^{2+}$, $Dy^{3+}$ co-doped ${SrAl_2}{O_4}$ phosphors have been synthesized by conventional solid state method. Photocurrent properties of $Eu^{2+}$ doped ${SrAl_2}{O_4}$ and $Eu^{2+}$, $Dy^{3+}$ co-doped ${SrAl_2}{O_4}$ phosphors, in order to elucidate $Dy^{3+}$ co-doping effect, during and after ceasing ultraviolet-ray (UV) irradiation have been investigated. The photocurrent of $Eu^{2+}$, $Dy^{3+}$ co-doped ${SrAl_2}{O_4}$ phosphors during UV irradiation was 4-times lower than that of $Eu^{2+}$-doped ${SrAl_2}{O_4}$ during UV irradiation, and 7-times higher than that of $Eu^{2+}$-doped ${SrAl_2}{O_4}$ after ceasing UV irradiation. The photocurrent results indicated that holes of charge carriers captured in hole trapping center during the UV irradiation and liberated after-glow process, and made clear that $Dy^{3+}$ of co-dopant acted as a hole trap. The photocurrent of ${SrAl_2}{O_4}$ showed a good proportional relationship to UV intensity in the range of $1{\sim}5mW/cm^2$, and $Eu^{2+}$-doped ${SrAl_2}{O_4}$ was confirmed to be a possible UV sensor.