• JSTS:Journal of Semiconductor Technology and Science
• /
• 제11권3호
• /
• pp.153-161
• /
• 2011

In this work, we report the physics-based SPICE model of amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) and demonstrate the SPICE simulation of amorphous InGaZnO (a-IGZO) TFT inverter by using Verilog-A. As key physical parameter, subgap density-of-states (DOS) is extracted and used for calculating the electric potential, carrier density, and mobility along the depth direction of active thin-film. It is confirmed that the proposed DOS-based SPICE model can successfully reproduce the voltage transfer characteristic of a-IGZO inverter as well as the measured I-V characteristics of a-IGZO TFTs within the average error of 6% at $V_{DD}$=20 V.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
• /
• pp.43-46
• /
• 2000

In this paper, the stress and transient currents associated with the on and off time of applied voltage were used to measure the density and distribution of high voltage stress induced traps in thin silicon oxide films. The transient currents were due to the discharging of traps generated by high stress voltage in the silicon oxides. The trap distributions were relatively uniform near both cathode and anode interface. The trap densities were dependent on the stress polarity. The stress generated trap distributions were relatively uniform the order of $10^{11}\sim10^{21}$[states/eV/$cm^2$] after a stress. The trap densities at the oxide silicon interface after high stress voltages were in the $10^{10}\sim10^{13}$[states/eV/$cm^2$]. It appear that the stress and transient current that flowed when the stress voltage were applied to the oxide was caused by carriers tunneling through the silicon oxide by the high voltage stress generated traps.

• 한국전기전자재료학회논문지
• /
• 제13권8호
• /
• pp.643-650
• /
• 2000

Density-of-states effective mass(m*$_{d}$) and conductivity mass(m*$_{c}$)for Ge and Ge$_{0.8}$/Sn$_{0.2}$ are obtained by using 8$\times$8 k.p and strain Hamiltonians. It is shown that m*$_{d}$ and m*$_{c}$ for electrons in Ge/Ge$_{0.8}$/Sn$_{0.2}$(001) and Ge$_{0.8}$/Sn$_{0.2}$/Ge(001) are much smaller than those for electrons in relaxed Ge mainly due to the increase of interaction caused by the strain between the conduction band and valence bands at the $\Gamma$ point. The lift of degeneracy in Ge/Ge$_{0.8}$/Sn$_{0.2}$(001) and Ge/Ge$_{0.8}$/Sn$_{0.2}$(001) makes m*$_{d}$ and m*$_{c}$ for holes smaller than those in relaxed Ge and results in the decrease of the interband scattering as well as interband scattering. The decrease of the interband scattering is more obvious in Ge/Ge$_{0.8}$/Sn$_{0.2}$(001) because of its large splitting energy between the heavy hole and light hole band. Therefore, Ge/Ge$_{0.8}$/Sn$_{0.2}$(001) is expected to be good candidate for the development of ultra high-speed CMOS device.CMOS device.eed CMOS device.CMOS device.

• 농업과학연구
• /
• 제44권4호
• /
• pp.504-512
• /
• 2017

Forest roads are essential for forest resource management. This study investigated and compared forest road and road policy data in Korea and the United States to improve future forest road policies in Korea. As compared to the United States (9.5 m/ha), Korea has much lower forest road density (3.19 m/ha) and has been actively constructing new forest roads. The Korea Forest Service leads forest road policy in Korea by providing subsidies for new road construction in non-national forests. The budget for forest roads accounted for 9.1% of the total Korea Forest Service budget in 2010 - 2015 and 73.5% of it was used for new road construction. Korean forest road policies have been distinctively changed over the past decades; e.g., an increase in forest road mileage in the 1990s, an increase in forest road standards in the 2000s, and an increase in the mileage of higher standard roads in the 2010s. In comparison to Korea, the United States has focused on road maintenance and road decommissioning since 2001. The budget for forest roads accounted for 2.9% of the total USDA Forest Service budget in 2011 - 2016 and 82.2% of it was used for operations and maintenance. Our study results suggest that forest road policies in Korea should start focusing on road maintenance and decommissioning, if needed.

• Bulletin of the Korean Chemical Society
• /
• 제14권2호
• /
• pp.238-243
• /
• 1993

A self-consistent-field Green's matrix method for the calculation of electronic properties of chemisorbed system is devised and applied to the methanol on copper(110) surface. The method is based on CNDO Hartree-Fock approximation. Contour integration in the complex energy plane is used for an efficient calculation of the charge-density bond-order matrix. The information on each fragment prior to chemisorption is efficiently used and a small number of iterations are needed to reach the self-consistency. The changes of density of states and other quantities of methanol due to chemisorption are consistent with reported experimental results.

• Bulletin of the Korean Chemical Society
• /
• 제19권5호
• /
• pp.553-557
• /
• 1998

Density functional theory calculations are reported for the carbon clusters bonded with two oxygen atoms $OC_No$ (n=2-6). The structures, vibrational frequencies and dipole moments are computed by BLYP theory with the 6-311G* basis set. Good agreement is obtained between the computed and experimentally observed properties. The ground states of these molecules are shown to be linear. Cyclic structures with higher energy are also predicted.

• Environmental Engineering Research
• /
• 제16권1호
• /
• pp.29-34
• /
• 2011

The electric charge on a membrane was investigated by analyzing the experimental rejection of various monovalent and divalent ionic solutes. The characteristics of the separation of ionic solutes using various nanofiltration membranes were obtained from an experimental nanofiltration set-up, with a surface area of $40cm^2$ under the operational pressures between 0.25-0.3 MPa. The state of the membrane electric charge was observed using separation coefficients, i.e., the permeation ratio of monovalent to divalent ions. To confirm the state of the membrane charge observed via the separation coefficient, a calculation using the extended Nernst-Planck equation, coupled with the Donnan equilibrium, assuming different electric charge states of the membrane, was compared with the experimental rejection of ionic solutes. The examination of the characteristics of separation using three types of nanofiltration membranes showed that one of the membranes carried a negative/positive double charge density inside, while other two membranes carried either a positive or negative charge density.

• Kyungpook Mathematical Journal
• /
• 제59권1호
• /
• pp.47-63
• /
• 2019

For $y{\in}{\mathbb{R}}$, a sequence $x=(x_n){\in}{\ell}^{\infty}$, and a non-negative regular matrix A, Bartoszewicz et. al., in 2015, defined the notion of the A-density ${\delta}_A(y)$ of the indices of those $x_n$ that are close to y. Their main result states that if the set of limit points of ($x_n$) is countable and density ${\delta}_A(y)$ exists for any $y{\in}\mathbb{R}$ where A is a non-negative regular matrix, then ${\lim}_{n{\rightarrow}{\infty}}(Ax)_n={\sum}_{y{\in}{\mathbb{R}}}{\delta}_A(y){\cdot}y$. In this note we first show that the result can be extended to a more general class of matrices and then consider a conjecture which naturally arises from our investigations.

• 한국초전도ㆍ저온공학회논문지
• /
• 제21권3호
• /
• pp.6-12
• /
• 2019

Extended Drude model has been used to obtain information of correlations from measured optical spectra of strongly correlated electron systems. The optical self-energy can be defined by the extended Drude model formalism. One can extract the optical self-energy and the electron-boson spectral density function from measured reflectance spectra using a well-developed usual process, which is consistent with several steps including the extended Drude model and generalized Allen's formulas. Here we used a reverse process of the usual process to investigate the extended Drude analysis when an additional low-energy interband transition is included. We considered two typical electron-boson spectral density model functions for two different (normal and d-wave superconducting) material states. Our results show that the low-energy interband transition might give significant effects on the electron-boson spectral density function obtained using the usual process. However, we expect that the low-energy interband transition can be removed from measured spectra in a proper way if the transition is well-defined or well-known.

• 한국광학회지
• /
• 제11권6호
• /
• pp.441-446
• /
• 2000

Balanced Homodyne Detection 방법으로 국소 진동자의 위상을 조절해 주면서, 각 위상에 대하여 광전류를 측정하여 전류세기의 분포함수를 구하여 이 값을 라돈 역변환을 포함한 Filtered Back Projection하여 빛의 양자역학적 상태를 규정하는 위그너 함수를 구하고 이로부터 간접적으로 밀도행렬을 구한다. 또 위상에 관계없이 구해진 분포함수에서 Pattern함수를 이용하여 밀도행렬을 구할 수 있다. 본 연구에서는 위의 모든 과정을 전산시늉을 통하여 여러 양자역학적 상태 입력 광에 대하여 예측되는 위그너 함수와 밀도 행렬을 구하였다.