• 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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• 제31A권8호
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• pp.34-45
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• 1994

We studied threshold voltages and I-V characteristics. considering short channel effect of the fully depleted thin film n-channel SOI MOSFET. We presented a charge sharing model when the back surface of short channel shows accumulation depletion and inversion state respectively. A degree of charge sharing can be compared according to each of back-surface conditions. Mobility is not assumed as constant and besides bulk mobility both the mobility defined by acoustic phonon scattering and the mobility by surface roughness scattering are taken into consideration. I-V characteristics is then implemented by the mobility including vertical and parallel electric field. kThe validity of the model is proved with the 2-dimensional device simulation (MEDICI) and experimental results. The threshold voltage and charge sharing region controlled by source or drain reduced with increasing back gate voltage. The mobility is dependent upon scattering effect and electric field. so it has a strong influence on I-V characteristics.

• 전기전자학회논문지
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• 제22권2호
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• pp.446-454
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• 2018

In this work, we summarize the calculation processes of obtaining a scattering factor using with the equilibrium average projection scheme (EAPS), with moderately weak coupling (MWC) interaction, and obtain the line-shape formula of an electron-deformation phonon interacting system interested in the confinement of electrons by squarwell confinement potentials in quantum two dimensional system.. Through the numerical analysis, we analysis the magnetic dependence of absorption power, P(B) in several temperature and frequency difference dependence of absorption power $P({\Delta}{\omega})$, in several external field, where ${\Delta}{\omega}={\omega}-{\omega}_0$ and ${\omega}({\omega}_0)$ is the angular frequency (the cyclotron resonance frequency). The result of equilibrium average projection scheme (EAPS) in SER-MWC explains the properties of quantum transition quite well.

• 한국진공학회지
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• 제12권S1호
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• pp.36-39
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• 2003

Field-domain dynamics and current self-oscillations are theoretically studied in quantum-well (QW) negative-effective-mass (NEM) $p^{+}pp^{+}$ diodes when the electric field is applied along the direction of the well. The origin of current self-oscillations is the formation and traveling of electric-field domains in the p-base. We have accurately considered the scattering contributions from carrier-impurity, carrier-acoustic phonon, and carrier-optic phonon. It's indicated that, both the applied bias and the doping concentration largely influence the current patterns and self-oscillating frequencies, which lie in the THz range for the NEM $p^{+}pp^{+}$ diode with a submicrometer p-base. The complicated field-domain dynamics is presented with the applied bias as the controlling parameter.

• Nuclear Engineering and Technology
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• 제50권5호
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• pp.731-737
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• 2018

In this research paper, the thermal transport in thorium dioxide is investigated by using nonequilibrium molecular dynamics. The thermal conductivity of bulk thorium dioxide was measured to be 20.8 W/m-K, confirming reported values, and the phonon mean free path was estimated to be between 7 and 8.5 nm at 300 K. It was observed that the thermal conductivity of thorium dioxide shows a strong dependency on temperature; the highest thermal conductivity was estimated to be 77.3 W/m-K at 100 K, and the lowest thermal conductivity was estimated to be 4.3 W/m-K at 1200 K. In addition, by simulating thorium dioxide structures with different lengths at different temperatures, it was identified that short wavelength phonons dominate thermal transport in thorium dioxide at high temperatures, resulting in decreased intrinsic phonon mean free paths and minimal effect of boundary scattering while long wavelength phonons dominate the thermal transport in thorium dioxide at low temperatures.

• Current Applied Physics
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• 제18권11호
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• pp.1338-1344
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• 2018

Band parameters and superconductivity of yttrium hypocarbide ($Y_2C$) have been investigated. The computations are performed using first-principles pseudopotential method within a generalized gradient approximation. The equilibrium lattice parameters have been determined and compared with experiment. Moreover, the material of interest is found to be stiffer for strains along the a-axis than those along the c-axis. A band-structure analysis of $Y_2C$ implied that the latter has a metallic character. The examination of Eliashberg Spectral Function indicates that Y-related phonon modes as well as C-related phonon modes are considerably involved in the progress of scattering of electrons. By integrating this function, the value of the average electron-phonon coupling parameter (${\lambda}$) is found to be 0.362 suggesting thus that $Y_2C$ is a weak coupling Bardeen-Copper-Schrieffer superconductor. The use of a reasonable value for the effective Coulomb repulsion parameter (${\mu}^*=0.10$) yielded a superconducting critical temperature $T_c$ of 0.59 K which is comparable with a previous theoretical value of 0.33 K. Upon compression (at pressure of 10 GPa) ${\lambda}$ and $T_c$ are increased to be 0.366 and 0.89 K, respectively, showing thus the pressure effect on the superconductivity in $Y_2C$. The spin-polarization calculations showed that the difference in the total energy between the magnetic and non-magnetic $Y_2C$ is weak.

• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2556-2566
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• 2023

A first-principle approach within the framework of density functional theory was employed to study the effect of vacancy defects and fission products (FPs) doping on the mechanical, electronic, and thermodynamic properties of uranium monocarbide (UC). Firstly, the calculated vacancy formation energies confirm that the C vacancy is more stable than the U vacancy. The solution energies indicate that FPs prefer to occupying in U site rather than in C site. Zr, Mo, Th, and Pu atoms tend to directly replace U atom and dissolve into the UC lattice. Besides, the results of the mechanical properties show that U vacancy reduces the compressive and deformation resistance of UC while C vacancy has little effect. The doping of all FPs except He has a repairing effect on the mechanical properties of U_1-xC. In addition, significant modifications are observed in the phonon dispersion curves and partial phonon density of states (PhDOS) of UC_1-x, Zr_xU_1-xC, Mo_xU_1-xC, and Rh_xU_1-xC, including narrow frequency gaps and overlapping phonon modes, which increase the phonon scattering and lead to deterioration of thermal expansion coefficient (α_V) and heat capacity (C_p) of UC predicted by the quasi harmonic approximation (QHA) method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.51-54
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• 1996

This paper reports the studies of the inversion layer mobility in p-channel Si MOSFET's under hot-carrier degradated condition. The validity of relationship of hot carrier degradations between the surface effective mobility and field effect mobility and are examined. The effective mobility(${\mu}$$\_$eff/) is derived from the channel conductances, while the field-effect mobility(${\mu}$$\_$FE/) is obtained from the transconductance. The characteristics of mobility curves can be divided into the 3 parts of curves. It was reported that the mobility degradation is due to phonon scattering, coulombic scattering and surface roughness. We are measured the mobility slope in curves with DC-stress [V$\_$g/=-3.1v]. It was found that the mobility(${\mu}$$\_$eff/ and ${\mu}$$\_$FE/) of p-MOSFET's was increased by increasing stress time and decreasing channel length. Because of the increasing stress time and increasing V$\_$g/ is changed oxide reliability and increased vertical field.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2009년도 Korea Superconductivity Society Meeting 2009
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• pp.4-4
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• 2009

• 한국세라믹학회지
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• 제40권6호
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• pp.560-565
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• 2003

방전 플라즈마 소결법(SPS: Spark Plasma Sintering)을 이용하여 800~100$0^{\circ}C$의 낮은 소결 온도에서 완전 치밀화를 이루는 M-doped ZnO를 (M=Al, Ni) 제조하여 그 소결 특성과 미세구조를 분석하였다. 전자현미경 분석 결과, NiO의 첨가는 ZnO 결정격자와의 고용체 형성을 촉진시키고 결정립 성장을 유발하였고, A1$_2$O$_3$는 순수한 ZnO 소결 시 나타나는 입계에서의 증발현상을 제어하고, 이차상 형성을 통하여 결정립 성장을 억제함을 확인할 수 있었다 NiO와 $Al_2$O$_3$를 동시에 첨가한 시편이 가장 우수한 미세구조가 형성됨을 확인하였고, SEM-EBSP (Electron Back-scattered Diffraction Pattern) 분석 결과 또한 우수한 결정립계 분포를 가지고 있음을 확인하였다. 이러한, 소결체의 우수한 미세구조적 특징은 carrier 농도 증가에 따른 전기 전도도와 증가 및 phonon scattering 효과에 의한 열전도도의 감소 효과를 유발하여 ZnO의 열전 특성을 향상시키리라 사료된다.