• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.223-226
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• 1998

In this paper, we have investigated how morphology and electrical properties in Polyphenylene sulfide(PPS) are changed by uniaxial elongation. XRD pattern shows that interplanar distance and crystallinities are decreased by increasing elongation ratio. Electrical conduction mechanism of PPS is explained as schottky emission from analysis of electrical current. The electrical current is decreased by increasing elongation ratio. The conductivity is changed remarkably above the glass transition temperature around $(82^{\circ}C)$. The band gap of PPS is evaluated as 3.9-4(eV) from the results of photoconductivity. Increarnent of elongation ratio gives us some information about deep trap formation from photocurrent.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.6
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• pp.668-672
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• 2004

Upon Debye's dielectric relaxation theory, we tried simple determination method of trap level in organic EL materials. From dielectric measurements in the 20 Hz - 1 MHz frequency range and in the 150 K - 320K temperature range, the depth of traps in Alq$_3$ filled with remaining electrons was determinated. Comparing to other determination techniques like TSL, or TL, the apparatus all we need is just simple LCR meter, thermometer and cooling method(liquid nitrogen). The mean activation energy is about 0.20 eV. It is in good agreement with previous determinations by other techniques like TSL. This results consolidate the validity of Burrow's transport mechanism model. Further intensified experiment with UV light on the dielectric absorption(Photodipolair effect) was nevertheless disturbed by the photoconductivity component.

• Journal of the Korean Applied Science and Technology
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• v.18 no.1
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• pp.49-54
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• 2001

Ultra-thin films of organic charge transfer complex were prepared on a hydrophilic substrate by Langmuir-Blodgett(LB) technique. In this study, the photoelectric properties of a LB film consisting of (N-docosyl quinolinium)-TCNQ(1:2) complex was investigated. The visible light(${\lambda}$ : 700 nm) of xenon lamp was illuminated on the LB films and light absorptivity and photoconductivity were observed. The photocurrent increased linearly and was saturated at the light intensity of 23 ${\mu}W/cm^{2}$.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.5
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• pp.1-4
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• 1982

Single crystals of InSe were obtained by the Bridgman method. The crystal structure was hombohedral(R3m) with lattice paramete. a=4.02A, c=24.96A. At 300$^{\circ}$K the electrical conductivity was about ~10-2($\Omega$.cm)-1, reslpectively. The electrical conductivity type was n- type. The donor level located at 0.072eV below the conduction band. The Photosensitivity was observed in range from 840nm to 1120nm. The energy gap of InSe single crystal measured from the photoconductivity and the optical transmittance spectrum was 1.20eV, 1.21eV, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.117-123
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• 1998

We investigated the effect of mechanical backside damage in Czochralski grown silicon wafer. The intensity of mechanical damage was evaluated by minority carrier recombination lifetime by laser excitation/microwave reflection photoconductivity decay method, photo-acoustic displacement method, X-ray section topography, and wet oxidation/preferential etching methods. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and the photo-acoustic displacement values increased proportionally, and it was at Grade 1: Grade 2:Grade 3 = 1:19.6:41 that the normalized relative quantization ratio of excess photo-acoustic displacement in damaged wafer was calculated, which are normalized to the excess PAD from sample Grade 1.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.581-586
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• 1998

We investigated the effect of mechanical back side damage in Czochralski grown silicon wafer. The intensity of mechanical damage was evaluated by minority carrier recombination lifetime by laser excitation/microwave reflection photoconductivity decay method, degree of X-ray diffuse scattering, X-ray section topography, and wet oxidation/preferential etching methods. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and the magnitude of diffuse scattering and X-ray excess intensity increased proportionally, and it was at Grade 1:Grade 2:Grade 3=1:7:18.4 that the normalized relative quantization ratio of excess intensity in damaged wafer was calculated, which are normalized to the excess intensity from sample Grade 1.

• Applied Science and Convergence Technology
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• v.26 no.3
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• pp.47-49
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• 2017

Photocurrent enhancement has been investigated in monolayer (1L) $MoS_2$ with PbS quantum dots (QDs). A metal-semiconductor-metal (Au-1L $MoS_2$-Au) junction device is fabricated using a standard photolithography method. Considerably improved photo-electrical properties are obtained by coating PbS QDs on the Au-1L $MoS_2$-Au device. Time dependent photoconductivity and current-voltage characteristics are investigated. For the QDs-coated $MoS_2$ device, it is observed that the photocurrent is considerably enhanced and the decay life time becomes longer. We propose that carriers in QDs are excited and transferred to the $MoS_2$ channel under light illumination, improving the photocurrent of the 1L $MoS_2$ channel. Our experimental findings suggest that two-dimensional layered semiconductor materials combined with QDs could be used as building blocks for highly-sensitive optoelectronic detectors including radiation sensors.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.230-234
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• 2001

We report a simple method for determining photovoltaic constant and conductivities of any photorefractive crytals which have no inversion symmetry by utilizing the electric field dependence of non-phase-matched second harmonic generation. New theoretical expression for the electric field dependence of Maker fringes is derived and space charge field can be determined using this from the observed change of intensity of second harmonic wave. The photovoltaic constant, dark conductivity and photoconductivity are easily deduced from an analysis of the measured relaxation behavior of space-charge field at two different light intensities. We demonstrate this method for $LiNbO_3$ at 514.5 nm.4.5 nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1030-1033
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• 2003

This paper presents the deposition characterization of polycrystalline silicon films by the HWCVD(Hot-wire Chemical Vapor Deposition) method at low substrate($300^{\circ}C$). The filament temperature, pressure and $SiH_4$ concentration were determined to be a critical parameter for the deposition of poly-Si films. Series A was deposited under the conditions of $1380^{\circ}C$(Tf), 100 mTorr and $2{\sim}10%\{SiH_4/(SiH_4+H_2)\}$ for 60 min. Series B was deposited under the conditions of $1400{\sim}1450^{\circ}C$ (Tf), 30 mTorr and $2{\sim}12%$ for 60 min. The physical characteristics were measured by Raman and FTIR spectroscopy, dark and photoconductivity measurements under AM1.5 illumination.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.113-113
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• 1998

C CdTe와 HgCdTe는 광전소자나 태양전지,x 선 및 y 선 감지 소자 그리고 적외선 감지소 자로의 웅용둥으로 인하여 많은 연구가 진행되고 있다. 광전소자를 제작함에 있어서 깊은 준위나 얄은 준위에 있는 몇들은 운반자 수명에 매우 큰 영향을 미치고 있음에도 불구하고 광전도도 측정에 의한 운반자 수명 연구에 대하여는 보고된 것이 별로 없다. 이에 본 논문에서는 CdTe 시료의 광전도도를 측정하여 운반자 수명 및 깊은 준위의 위치를 알아보았다 M MBE방법을 이용하여 CdTe 기판위에 In을 도핑한 CdTe를 성장하였다. 광전도 붕괴(PCD) 측정은 300 K에서부터 400 K까지 온도를 변화시켜주면서 측정을 하였고 광원으로서 G GaP- LED를 사용하였으며 전압 신호를 읽기 위하여 Tektronix 2430A 오실로스코프를 이용하 였다 .. Fig. 1. 에서 보인바와 같이 광전도 붕괴곡선은 접선으로 나타낸 하나의 지수 함수적 붕 괴(a2exp( -t/ r 2))보다는 설선으로 나타낸 두 개의 지수함수적 붕괴(alexp( νr 1)+a2exp( -νr 2)) 가 더욱 잘 실험결과와 일치함을 알 수 있었다. 이러한 것은 과잉 전하에 대한 깊은준위를 가 지고 있는 반도체물질에서 일반적으로 관찰되는 것으로 시료가 n 형이기 때문에 소수 운반자 인 정공의 벚에 의한 것으로 생각된다 .. Fig. 2. 에서는 운반자 수명의 온도에 대한 변화를 나타 낸 것이다. 온도가 증가함에 따라 운반자 수명이 감소하는 경항올 보이고 있으며 이것올 이용 하여 딪익 활성화 에너지를 계산 하여 본 결과 0.35 eV 와 0.43 eV염을 알수 있었다.