• 한국토양비료학회지
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• 제49권5호
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• pp.548-554
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• 2016

Optimal range of soil physical quality to enhance crop productivity or to improve environmental health is still in dispute for the upland soil. We hypothesized that the optimal range might be established by comparing soil physical parameters and their interactions inhibiting crop growth. The parameter identifying optimal range covered favorable conditions of aeration, permeability and root extension. To establish soil physical standard two experiments were conducted as follows; 1) investigating interactions of bulk density and aeration porosity in the laboratory test and 2) determining effects of soil compaction and deep & conventional tillage on physical properties and crop growth in the field test. The crops were Perilla frutescens, Zea mays L., Solanum tuberosum L. and Secale cereael. The saturated hydraulic conductivity, bulk density from the root depth, root growth and stem length were obtained. Higher bulk density showed lower aeration porosity and hydraulic conductivity, and finer texture had lower threshold bulk density at 10% aeration bulk density. Reduced crop growth by subsoil compaction was higher in silt clay loam compared to other textures. Loam soil had better physical improvement in deep rotary tillage plot. Combined with results of the present studies, the soil physical quality was possibly assessed by bulk density index. Threshold subsoil bulk density as the upper value were $1.55Mg\;m^{-3}$ in sandy loam, $1.50Mg\;m^{-3}$ in loam and $1.45Mg\;m^{-3}$ in silty clay loam for optimal soil physical quality in upland.

• Transactions on Electrical and Electronic Materials
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• 제18권1호
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• pp.51-54
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• 2017

TFTs (thin film transistors) were fabricated using a-SIZO (amorphous silicon-indium-zinc-oxide) channel by RF (radio frequency) magnetron sputtering at room temperature. We report the influence of various channel thickness on the electrical performances of a-SIZO TFTs and their stability, using TS (temperature stress) and NBTS (negative bias temperature stress). Channel thickness was controlled by changing the deposition time. As the channel thickness increased, the threshold voltage ($V_{TH}$) of a-SIZO changed to the negative direction, from 1.3 to -2.4 V. This is mainly due to the increase of carrier concentration. During TS and NBTS, the threshold voltage shift (${\Delta}V_{TH}$) increased steadily, with increasing channel thickness. These results can be explained by the total trap density ($N_T$) increase due to the increase of bulk trap density ($N_{Bulk}$) in a-SIZO channel layer.

• 진공이야기
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• 제3권1호
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• pp.16-21
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• 2016

FinFETs are able to be scaled down to 22 nm and beyond while suppressing effectively short channel effect, and have superior performance compared to 2-dimensional (2-D) MOSFETs. Bulk FinFETs are built on bulk Si wafers which have less defect density and lower cost than SOI(Silicon-On-Insulator) wafers. In contrast to SOI FinFETs, bulk FinFETs have no floating body effect and better heat transfer rate to the substrate while keeping nearly the same scalability. The bulk FinFET has been developed at 14 nm technology node, and applied in mass production of AP and CPU since 2015. In the development of the bulk FinFETs at 10 nm and beyond, self-heating effects (SHE) is becoming important. Accurate control of device geometry and threshold voltage between devices is also important. The random telegraph noise (RTN) would be problematic in scaled FinFET which has narrow fin width and small fin height.

• 한국재료학회지
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• 제33권7호
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• pp.273-278
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• 2023

In this study, based on the saturation magnetic flux density experimental values (B_s) of 622 Fe-based bulk metallic glasses (BMGs), regression models were applied to predict B_s using artificial neural networks (ANN), and prediction performance was evaluated. Model performance evaluation was investigated by using the F1 score together with the coefficient of determination (R² score), which is mainly used in regression models. The coefficient of determination can be used as a performance indicator, since it shows the predicted results of the saturation magnetic flux density of full material datasets in a balanced way. However, the BMG alloy contains iron and requires a high saturation magnetic flux density to have excellent applicability as a soft magnetic material, and in this study F1 score was used as a performance indicator to better predict B_s above the threshold value of B_s (1.4 T). After obtaining two ANN models optimized for the R² and F1 score conditions, respectively, their prediction performance was compared for the test data. As a case study to evaluate the prediction performance, new Fe-based BMG datasets that were not included in the training and test datasets were predicted using the two ANN models. The results showed that the model with an excellent F1 score achieved a more accurate prediction for a material with a high saturation magnetic flux density.

• 한국세라믹학회지
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• 제33권5호
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• pp.547-555
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• 1996

Porous alumina ceramics were fabricated by pseudo-boehmite phydosol-gel process within/without commercial $\alpha$-alumina particles average 1 and 40 micron respectively. The pore characteristics of fired specimens were studied by the measurement of bulk density total porosity thyermal analysis pore volume pore distribution BET area XRD and SEM. with increasing of firing temperature pore volume and BET surface area were decreased and the average pore size was increased to approximately 146$\AA$ upto 80$0^{\circ}C$ by de-watering of [OH] and formation of $\alpha$-alumina. The fired relative density of the alumina-dispersed specimen with average 1 micron particle was increased with the amounts of dispersed particle by bimodal packing theory which is compared to the ones of specimen including of average 40 micron particle. It was confirmed that the percola-tion threshold in porous ceramics with coarser particle (40 micron) has formed between the transformed-alumina from hydrogel and dispersed-alumina of above 50 vol% particle and the total porosity was increased at the threshold point above.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권3호
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• pp.158-166
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• 2001

Based on uniform hot carrier injection (optically assisted electron injection) across the $Si-SiO_2$ interface into the gate insulator of n-channel IGFETs, the threshold voltage shifts associated with electron injection of $1.25{\times}l0^{16}{\;}e/\textrm{cm}^2 between 0.5 and 7 MV/cm were found to decrease from positive to negative values, indicating both a decrease in trap cross section ($E_{ox}{\geq}1.5 MV/cm$) and the generation of FPC $E_{ox}{\geq}5{\;}MV/cm$). It was also found that FNC and large cross section NETs were generated for $E_{ox}{\geq}5{\;}MV/cm$. Continuous, uniform low-field (1MV/cm) electron injection up to $l0^{19}{\;}e/\textrm{cm}^2 is accompanied by a monatomic increase in threshold voltage. It was found that the data could be modeled more effectively by assuming that most of the threshold voltage shift could be ascribed to generated bulk defects which are generated and filled, or more likely, generated in a charged state. The injection method and conditions used in terms of injection fluence, injection density, and temperature, can have a dramatic impact on what is measured, and may have important implications on accelerated lifetime measurements.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1679-1684
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• 2011

Interfacial reactions kinetics often differ from kinetics of bulk reactions. Here, we describe how the density change of an immobilized reactant influences the kinetics of interfacial reactions. Self-assembled monolayers (SAMs) of alkanethiolates on gold were used as a model interface and the Diels-Alder reaction between immobilized quinones and soluble cyclopentadiene was used as a model reaction. The kinetic behavior was studied using varying concentrations of quinones. An unusual threshold density of quinones (${\Gamma}_c$ = 5.2-7.2%), at which the pseudo-first order rate constant started to vary as the reaction progressed, was observed. This unexpected kinetic behavior was attributed to the phase-separation phenomena of multi-component SAMs. Additional experiments using more phase-separated two-component SAMs supported this explanation by revealing a significant decrease in ${\Gamma}_c$ values. When the background hydroxyl group was replaced with carboxylic or phosphoric acid groups, ${\Gamma}_c$ was observed at below 1%. Also, more phase-separated thermodynamically controlled SAMs produced a lower critical density (3% < ${\Gamma}_c$ < 4.9%) than that of the less phaseseparated kinetically controlled SAMs (6.5% < ${\Gamma}_c$ < 8.9%).

• 전자통신동향분석
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• 제5권1호
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• pp.55-70
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• 1990

SIMOX SOI is known to be one of the most useful technologies for fabrications of new generation ULSI devices. This paper describes the current status of SIMOX SOI technology for ULSI applications. The SIMOX wafer is vertically composed of buried oxide layer and silicon epitaxial layer on top of the silicon substrate. The buried oxide layer is used for the vertical isolation of devices The oxide layer is formed by high energy ion implantation of high dose oxygen into the silicon wafer, followed by high temperature annealing. SIMOX-based CMOS fabrication is transparent to the conventional IC processing steps without well formation. Furthermore, thin film CMOX/SIMOX can overcome the technological limitations which encountered in submicron bulk-based CMOS devices, i.e., soft-error rate, subthreshold slope, threshold voltage roll-off, and hot electron degradation can be improved. SIMOX-based bipolar devices are expected to have high density which comparable to the CMOX circuits. Radiation hardness properties of SIMOX SOI extend its application fields to space and military devices, since military ICs should be operational in radiation-hardened and harsh environments. The cost of SIMOX wafer preparation is high at present, but it is expected to reduce as volume increases. Recent studies about SIMOX SOI technology have demonstrated that the performance of the SIMOX-based submicron devices is superior to the circuits using the bulk silicon.

• 한국전기전자재료학회논문지
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• 제13권9호
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• pp.729-734
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• 2000

Recently, Very Large Scale Integrated (VLSI) circuit & deep-submicron bulk Complementary Metal Oxide Semiconductor(CMOS) devices require gate electrode materials such as metal-silicide, Titanium-silicide for gate oxides. Many previous authors have researched the improvement sub-micron gate oxide quality. However, few have reported on the electrical quality and reliability on the ultra thin gate oxide. In this paper, at first, I recommand a novel shallow trench isolation structure to suppress the corner metal-oxide semiconductor field-effect transistor(MOSFET) inherent to shallow trench isolation for sub 0.1${\mu}{\textrm}{m}$ gate oxide. Different from using normal LOCOS technology deep-submicron CMOS devices using novel Shallow Trench Isolation(STI) technology have a unique"inverse narrow-channel effects"-when the channel width of the devices is scaled down, their threshold voltage is shrunk instead of increased as for the contribution of the channel edge current to the total channel current as the channel width is reduced. Secondly, Titanium silicide process clarified that fluorine contamination caused by the gate sidewall etching inhibits the silicidation reaction and accelerates agglomeration. To overcome these problems, a novel Two-step Deposited silicide(TDS) process has been developed. The key point of this process is the deposition and subsequent removal of titanium before silicidation. Based on the research, It is found that novel STI structure by the SEM, in addition to thermally stable silicide process was achieved. We also obtained the decrease threshold voltage value of the channel edge. resulting in the better improvement of the narrow channel effect. low sheet resistance and stress, and high threshold voltage. Besides, sheet resistance and stress value, rms(root mean square) by AFM were observed. On the electrical characteristics, low leakage current and trap density at the Si/SiO$_2$were confirmed by the high threshold voltage sub 0.1${\mu}{\textrm}{m}$ gate oxide.

• 대한산업공학회지
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• 제21권3호
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• pp.345-356
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• 1995

The aim of this paper is to analyze the batch service queueing model M/M(a, b ; ${\mu}_k/1$) under general bulk service rule with mean service rate ${\mu}_k$ for a batch of k units, where $a{\leq}k{\leq}b$. This queueing model consists of the two-dimensional state space so that it is characterized by two-dimensional state Markov process. The steady-state solution and performane measure of this process are derived by using Matrix Geometric method. Meanwhile, a new approach is suggested to calculate the two-dimensional traffic density R which is used to obtain the steady-state solution. In addition, to determine the optimal service initiation threshold a, a decision model of this queueing system is developed evaluating cost of service per batch and cost of waiting per customer. In a job order production system, the decision-making procedure presented in this paper can be applicable to determining when production should be started.