• Journal of the Korean Society for Heat Treatment
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• v.30 no.6
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• pp.258-263
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• 2017

The effect of cooling rate on the damping capacity of pure Mg was studied. Two Mg samples with different cooling rates were prepared by heat treatment at 873 K for 24 h, followed by water quenching and by furnace cooling to room temperature, respectively. The average grain sizes of the Mg samples were almost identical regardless of the cooling rate, but more twins were observed in the sample with faster cooling rate. The calculated vacancy fraction was higher in the fast cooling sample than the slow cooling one. It is noted that the fast cooling sample exhibited lower damping capacity both in the strain-amplitude independent and strain-amplitude dependent regions. Higher values of vacancy concentration and number density of twins in the fast cooling sample are considered to be responsible for the deteriorated damping capacity in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

• Advances in nano research
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• v.15 no.1
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• pp.59-65
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• 2023

In this present article, the mechanical behavior of single-walled black phosphorene nanotubes (SW-αPNTs) is simulated using molecular dynamics (MD). The proposed model is subjected to the axial loading and the effects of morphological parameters, such as the mono-vacancy defect and strain rate on the tensile behavior of the zigzag and armchair SW-αPNTs are studied as a pioneering work. In order to assess the accuracy of the MD simulations, the stress-strain response of the current MD model is successfully verified with the efficient quantum mechanical approach of the density functional theory (DFT). Along with reproducing the DFT results, the accurate MD simulations successfully anticipate a significant variation in the stress-strain curve of the zigzag SW-αPNTs, namely the knick point. Predicting such mechanical behavior of SW-αPNTs may be an important design factor for lithium-ion batteries, supercapacitors, and energy storage devices. The simulations show that the ultimate stress is increased by increasing the diameter of the pristine SW-αPNTs. The trend is identical for the ultimate strain and stress-strain slope as the diameter of the pristine zigzag SW-αPNTs enlarges. The obtained results denote that by increasing the strain rate, the ultimate stress/ultimate strain are respectively increased/declined. The stress-strain slope keeps increasing as the strain rate grows. It is worth noting that the existence of mono-atomic vacancy defects in the (12,0) zigzag and (0,10) armchair SW-αPNT structures leads to a drop in the tensile strength by amounts of 11.1% and 12.5%, respectively. Also, the ultimate strain is considerably altered by mono-atomic vacancy defects.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.84-88
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• 1999

The behavior of oxygen precipitation was investigated in radial direction using Si wafers with different vacancy-related defects generation area. The behavior of oxygen precipitation in radial direction is strongly dependent on the size of vacancy rich area which is related with crystal growth condition. Oxygen precipitation rate is more enhanced in vacancy rich area than that of interstitial rich area. And anomalous oxygen precipitation is generated in the marginal bands of vacancy and interstial area. In V/I boundary, however, oxygen precipitation is suppressed to nearly perfect.

• Journal of the Semiconductor & Display Technology
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• v.15 no.1
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• pp.70-75
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• 2016

GZO films prepared on ITO glasses were annealed at various temperatures in a vacuum condition to research the relationship between oxygen vacancies and optical properties. GZO films after annealing in a vacuum showed the various optical-chemical properties depending on the annealing temperatures and oxygen gas flow rate during the deposition. The oxygen vacancy of GZO film prepared by oxygen gas flows of 22 sccm increased with increasing the annealing temperatures, because of the extraction of oxygen by the annealing. But the intensity of photoluminance of GZO with 22 sccm decreased in accordance with the annealing temperature, because of the reduction of ionized charge carriers. The oxygen vacancy by the extraction of oxygen enhanced a depletion, so the widen depletion had the strong Schottky barrier and the PL intensity due to the low carrier density decreased.

• Bulletin of the Korean Chemical Society
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• v.5 no.1
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• pp.41-44
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• 1984

The oxidation of carbon monoxide has been investigated on Ni-doped ${\alpha}-Fe_2O_3$ catalyst at 300 to $450^{\circ}$. The oxidation rates have been correlated with 1.5-order kinetics; first with respect to CO and 1/2 with respect to $O_2$. Carbon monoxide is adsorbed on lattice oxygen of Ni-doped ${\alpha}-Fe_2O_3$, while oxygen appears to be adsorbed on oxygen vacancy formed by Ni-doping. The conductivities show that adsorption of CO on O-lattice produces conduction electron and adsorption of $O_2$ on O-vacancy withdraws the conduction electron from vacancy. The adsorption process of CO on O-lattice is rate-determining step and dominant defect of Ni-doped ${\alpha}-Fe_2O_3$ is suggested from the agreement between kinetic and conductivity data.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.6
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• pp.17-26
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• 1984

A computer program (DIFSIM: Diffusion SIMulator) was written to calculate the impurity profile, specifically boron and phosphorus, due to three different diffusion processes-predeposition, drive-in in inert ambient, and drive-in in oxidizing ambient. The vacancy mechanism including Fair and Tsai's theory for phosphDrus diffusion was widely incorporated for modeling various diffusion processes. The concentrationtependent oxidation rate was also explained using the vacancy model, while the oxidation - enhanced diffusion was mo dolled using catkins replacement mochanlsm . The simulation results using DIFSIM showed a fairly good agreement with the experimental data by adjusting some of the empirical parameters in the program. The results obtained using DIFSIM were compared with the results from SUPREM II.

• Applied Science and Convergence Technology
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• v.25 no.6
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• pp.145-148
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• 2016

This paper, Al-doped ZnO(AZO) thin films for application as transparent conducting oxide films were deposited on the Corning glass substrate by using RF magnetron sputtering system. The effects of various Argon gas flow rates on optical and electrical characteristics of AZO films were investigate sputtering method. The Carrier Concentration is enhanced as Ar gas rate increases, and also the oxygen vacancy concentration. The figure of merit obtained in this study means that AZO films which deposited Ar gas rate of 75 sccm have the highest Carrier concentration and Hall mobility, which have the highest photoelectrical performance that it could be used as transparent electrodes.

• Journal of Labour Economics
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• v.42 no.4
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• pp.59-88
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• 2019

This study estimates causal effects of the governor vacancy on the regional economy, exploiting the case of exogenous governor vacancy in Korea. We find that the governor vacancy has a negative impact on the regional economy by lowering the employment rate and reducing the amount of credit card expenditures. Negative effects are more pronounced among vulnerable groups of the labor market such as women and aged 20~29 and 50~59. In addition, negative effects vary by characteristics of the governor. Negative effects of the governor vacancy on the regional economy show empirical evidence suggesting that leaders do matter.

• Journal of the Korean Electrochemical Society
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• v.22 no.1
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• pp.13-21
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• 2019

Prussian blue analogues(PBAs) are comprised of cyano-bridged transition metal ions. The wide and unique open-framework structures of the PBAs enable reversible intercalation and deintercalation of various ions such as $Na^+$, $K^+$, $Mg^{2+}$, $Zn^{2+}$, etc. In addition, since PBAs are synthesized through coprecipitation reaction in aqueous solution at room temperature, they are produced economically and environmentally friendly. However, the formation of crystals proceeds rapidly, and defects such as vacancy and crystal water tend to be present in the crystals, thereby affecting key battery performance. Therefore, significant efforts to inhibit defects in PBAs have been made. In the case of vacancy, the reaction rate was controlled at the synthesis stage to reduce the formation of vacancy, and the crystal water was removed by heat treatment under vacuum. In addition, by adding transition metals that do not react within the structure of PBA, the structural instability during the electrochemical reaction was largely alleviated.

• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.12-16
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• 2022

We have investigated the effect of the substrate temperature and hydrogen flow rate on the characteristics of IGZO thin films for the TCO (transparent conducting oxide). For this purpose, IGZO thin films were deposited by RF magnetron sputtering at room temperature and 300℃ with various H₂ flow rate. Experiments were carried out while varying the hydrogen gas flow rate from 0sccm to 1.0sccm in order to see how the hydrogen gas affects the IGZO thin films. IGZO thin films deposited at room temperature and 300℃ showed amorphous. The lowest resistivity value was 0.379×10^-5 Ωcm when the IGZO film was deposited at 300℃ and set up at 1.0sccm. As the oxygen vacancy rate increased, the resistivity intended to decrease. In conclusion, Oxygen vacancy affects the IGZO thin film's electrical characteristic.