• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1999년도 춘계종합학술대회
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• pp.389-393
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• 1999

디바이스 효율에 커다란 영향을 미치고 있는 임팩트이온화현상의 정확한 모델이 디바이스 시뮬레이션에 필수적인 요소가 되고 있다. 최근에는 정확한 GaAs 임팩트이온화 모델을 위해 각 에너지 범위에 파라서 7.8과 5.6의 지수를 갖는 수정된 Keldysh 공식이 사용되고 있다. 그러나 이 모델 또한 임팩트이온화의 방향성을 무시한 등방성 모델로서 저에너지에서 이방성을 보이는 임팩트이온화모델로서는 부적합하다. 임팩트이온화율은 낮은 전자에너지에서는 강한 이방성 성질을 나타내는 반면에, 임팩트이온화현상이 자주 발생하는 높은 에너지 범위에서는 등방성이 된다. 임팩트이온화율을 계산하기 위하여 Fermi 황금법칙과 의사 포텐셜방법에 의하여 계산된 full 에너지 밴드구조를 사용하였다. Form factor 및 실험값을 비교하였으며, 방향에 따른 전도대의 에너지 밴드 구조를 <100>, <110>, <111>의 방향에 대하여 조사하였다. 결과적으로, 임팩트이온화의 문턱에너지가 이방성을 갖음을 알 수 있었다. 또한 상대적으로 낮은 에너지 즉, 문턱에너지 근처에서 임팩트이온화율이 더욱 심하게 변화함을 알 수 있다.

• 한국표면공학회지
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• 제24권3호
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• pp.119-124
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• 1991

Recently, the trend of research in hard coating is concentrate on developing the process of ionization rate under low operating pressure, to get the thin film with high adhesion and dense microstructures. In this study ionization rate enhancement type PVD process using permanent magnet is developed, which enhances the ionization rate by confining the plasma suppressing the wall loss of electron. By the result to investigate the characteristic of glow discharge, the ionization rate of this process is enhanced about twice as high as that of triod BARE process (about 26%), and more dense TiN microstructures are obtained in this process. Cylindrical ion energy analyzer is made and attached in front of a quadrupole mass filter for the analysis of the energy distribution of reactive gas and activated gas ions from the plasma zone. To analyze the operation mechanism of ion energy analyzer, computer simulation is performed by calculation the electric field environment using finite element method. By these analyses of ion energy distribution of outcoming ions from the plasma zone, it is found that magnetic field enhances ion kinetic energy as well as ionization rate. The other results of this study is that the foundation of feed-back system is constructed, which automatically control the partial pressure of reactive gas. In can be possible by recording the data of mass spectrum and ion energy analysis using A-D converter.

• Journal of Radiation Protection and Research
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• 제34권2호
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• pp.77-81
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• 2009

An Area Radiation Monitoring System (ARMS) ionization chamber, which had an 11.8 L active volume, was fabricated and performance-tested at KAERI. Low leakage currents, linearities at low and high dose rates were achieved from performance tests. The correlation coefficients between the ionization currents and the dose rates are 1 at high dose rate and 0.99 at low dose rate. In this study, an integration-type ARMS ionization chamber was tested over a year for an evaluation of its long-term stability at a radioisotope (RI) repository of the Young-gwang nuclear power plant. The standard deviation of dose rate of 1 day data and over a 100-days mean value were 6.2 $\mu$R/h and 2.9 $\mu$R/h, respectively. The fabricated ARMS ionization chamber showed stable performance from the results of the long-term tests. Design and performance characteristics of the fabricated ionization chamber for the ARMS from performance-tests are also addressed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
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• pp.131-135
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• 1989

Hot electron simulation of silicon using Monte Carlo method was carried out to investigate impact ionization characteristics near the drain of MOSFET's at 77 and 300K. We successfully characterized drift velocity and impact ionization at 77 and 300K employing a simplified energy band structure and phonon scattering mechanisms. Woods' soft energy threshold model was introduced to the Monte Carlo simulation of impact ionization, and good agreement with reported experimental results was resulted by employing threshold energy of 1.7 eV. It is suggested that the choice of the critical angle between specular reflection and diffusive scattering of surface roughness scattering may be important in determining the impact ionization charateristics of Monte Carlo simulation near the drain of MOSFET's.

• 전자공학회논문지A
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• 제33A권11호
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• pp.112-119
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• 1996

Impact ionization model in GaAs has been presented by modified keldysh formula with two sets of power exponent of 7.8 and 5.6 in study. Impact ionization rate is derived from fermil's golden rule and ful lenergy band stucture based on empirical pseudopotential method. Impact ionization rates show anisotropic property in low energy region (<3eV), but isotropic in high energy region (3>eV). Full band monte calo simulator is coded for investigating the validity of the GaAs impact ionization model, and validity is checked by comparing impact ionization coefficients with experimental values and ones in anisotropic model. Valley transitions to energy alteration are explained by investigating electron motion in brillouin zone for full band model to electric field variation.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1999년도 추계종합학술대회
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• pp.520-524
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• 1999

임팩트이온화율은 낮은 전자에너지에서는 이방성이지만, 임팩트이온화가 자주 발생하는 높은 에너지 영역에서는 등방성이 된다. 본 연구에서는 300K와 77K에서의 임팩트이온화율을 계산하기 위하여 의사포텐셜 방법으로 구한 full 에너지 밴드 구조와 페르미의 황금법칙 군 사용하였다. 계산된 임팩트이온화율은 수정된 Keldysh공식을 사용하여 표현되었다. GaAs 임팩트이온화 모델의 타당성을 고찰하기 위해 Monte Carlo simulator를 제작하여 300K와 77K에서의 임팩트이온화 계수를 구하여 비교하였다 시뮬레이션 결과, 300K에서 임팩트이온화 과정의 이방성특성이 관찰되었지만, 77K에서는 거의 임팩트이온화 계수가 일정함을 입증하였다. 특히, 77K에서 <110>방향을 따라 적용된 전계에서는 이방성특성이 나타남을 입증하였다.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.815-820
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• 2014

We applied the two-color resonant two-photon ionization and mass-analyzed threshold ionization techniques to record the vibronic and cation spectra of 2,4-difluorophenol. As supported by our theoretical calculations, only the cis form of 2,4-difluorophenol involves in the two-photon photoexcitation and pulsed field ionization processes. The band origin of the $S_1{\leftarrow}S_0$ electronic transition of cis-2,4-difluorophenol appears at 35 647 ${\pm}2cm^{-1}$ and the adiabatic ionization energy is determined to be 70 $030{\pm}5cm^{-1}$, respectively. Most of the observed active vibrations in the electronically excited $S_1$ and cationic ground $D_0$ states mainly involve in-plane ring deformation vibrations. Comparing these data of cis-2,4-difluorophenol with those of phenol, cis-2-fluorophenol, and 4-fluorophenol, we found that there is an additivity rule associated with the energy shift resulting from the additional fluorine substitution.

• Bulletin of the Korean Chemical Society
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• 제25권1호
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• pp.101-105
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• 2004

The laser ablation/ionization time-of-flight mass spectrometry is applied to the isotopic analysis of solid samples using a home-made instrument. The technique is convenient for solid sample analysis due to the onestep process of vaporization and ionization of the samples. The analyzed samples were lead, cadmium, molybdenum, and ytterbium. To optimize the analytical conditions of the technique, several parameters, such as laser energy, laser wavelength, size of the laser beam on the samples surface, and high voltages applied on the ion source electrodes were varied. Low energy of laser light was necessary to obtain the optimal mass resolution of spectra. The 532 nm light generated mass spectra with the higher signal-to-noise ratio compared with the 355 nm light. The best mass resolution obtained in the present study is ~1,500 for the ytterbium.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 추계학술대회 논문집
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• pp.337-340
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• 2008

When high surge voltage invaded into the ground rod contacted with ground water, the ionization phenomena are happened in the water. Although some researchers have surveyed the ionization phenomena in soil, they have just analyzed the variation of the ground resistance. The most important role of the ground rod is to elect human beings from potential rise and to dissipate energy to the earth safely. In this wort we presented the method evaluating the potential reduction and energy dispersion. Also we analyzed theses factors as a function of charging voltages at the water resistivity of $50\;{\Omega}{\cdot}m$ using the Matlab Program. As a result the ground rod potential was reduced to 38 kV by ionization just below breakdown voltage. The energy more than half of the total injected energy was dispersed through the grounding electrode caused due to ionization.

• 한국정보통신학회논문지
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• 제4권3호
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• pp.697-703
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• 2000

임팩트이온화현상은 소자의 크기가 점점 작아지면서, 높은 에너지에 있는 hot carrier 전송 을 해석하기 위해 매우 중요하므로 소자의 시뮬레이션에 정확한 임팩트이온화모델이 필수적이다. 털 연구에서는 의사포텐셜방법을 사용하여 풀밴드모델을 구하고, 임팩트이온화율은 수정된 Keldysh 공식을 이용하여 유도하였다. 본 연구에서는 Gahs 임팩트이은화의 온도의존특성을 조사하기 위하여 Monte Carlo 시뮬레이터를 제작하여 임팩트이온화계수를 구하였다. 결과적으로, 임팩트이온화계수는 300K에서 실험값과 잘 일치하였다. 또한 에너지는 전계가 증가할수록 증가하고, 높은 온도에서는 포논 산란의 emission mode가 높기 때문에 에너지가 감소함을 알 수 있었다. 임팩트이온화의 대수 fitting 함수 식은 온도와 전계에 대해 2차식으로 표현하였다. 대수 fitting 함수의 오차는 대부분 5%이내에 머물렀다. 그러므로 대수식으로 표현된 임팩트 이온화계수는 온도에 의존함을 알았고, 임팩트이온화계수를 구하는데 시간을 절약할 수 있다.