XPS Study of Aluminum Oxides Deposited on PET Thin Film

Kim, Young Joo,Choi, Jeong Gil,Kwon, Moo Hyun,Kim, Jung Sik,Yang, Chang Soo,Kim, Geug Tae,Choi, Jang Woo 한국공업화학회 2000 Journal of Industrial and Engineering Chemistry Vol.6 No.3

Aluminum oxide thin films were deposited on PET substrate film using r.f. magnetron sputtering with an aluminum oxides magnetron target and argon plasma. The electronic structures of the resulting aluminum oxides were then examined using XPS. The XPS spectrum for the aluminum oxides showed the presence of a well-resolved A1 2p spectral line at 74.3±0.2 eV (FWHM=∼2.1). The binding energies of A1 2p and O 1s for the samples prepared under the synthetic conditions in the current study were the same, or very similar. The average ratio of O_o/Al for all the aluminum oxides was 2.8, thereby indicating that the deviation from the stoichiometric atomic ratio of 1.5 in A1₂O₃ was accounted for by incomplete oxidation. Given reference energies of 531.0 eV for O is and 72.7 eV for Al 2p, the A1 2p peak tended to shift to higher energies, while the O 1s peak shifted to lower energies. During the synthesis of the aluminum oxide thin films, there were correlations between the preparative conditions and the relative intensities of the Al 2p and O 1s peaks. The peak intensities of A1 2p and O is increased with an increase in both sputtering power and time. These results indicate a linear relationship between the peak intensities of A1 2p and O 1s and the power.

Essence of thermal convection for physical vapor transport of mercurous chloride in regions of high vapor pressures

Kim, Geug-Tae,Lee, Kyong-Hwan,Choi, Jeong-Gil The Korea Association of Crystal Growth 2007 韓國結晶成長學會誌 Vol.17 No.6

For an aspect ratio (transport length-to-width) of 5, Pr=3.34, Le=0.078, Pe=4.16, Cv=1.01, $P_B=50$ Torr, only thermally buoyancy-driven convection ($Gr=4.83{\times}10^5$) is considered in this study in spite of the disparity in the molecular weights of the component A ($Hg_2Cl_2$) and B which would cause thermally and/or solutally buoyancy-driven convection. The crystal growth rate and the maximum velocity vector magnitude are decreased exponentially for $3{\le}Ar{\le}5$, for (1) adiabatic walls and (2) the linear temperature profile, with a fixed source temperature. This is related to the finding that the effects of side walls tend to stabilize convection in the growth reactor. The rate for the linear temperature profiles walls is slightly greater than for the adiabatic walls far varied temperature differences and aspect ratios. With the imposed thermal profile, a fixed source region, both the rate and the maximum velocity vector magnitude increase linearly with increasing the temperature difference for $10{\le}{\Delta}T{\le}50K$.

Theoretical gravity studies on roles of convection in crystal growth of $Hg_2Cl_2$-Xe by physical vapor transport under normal and high gravity environments

Kim, Geug-Tae,Kwon, Moo-Hyun The Korea Association of Crystal Growth 2009 韓國結晶成長學會誌 Vol.19 No.3

Particular interest in the role of convection in vapor crystal growth has arisen since some single crystals under high gravity acceleration of $10g_0$ appear considerably larger than those under normal gravity acceleration ($1g_0$). For both ${\Delta}T=60\;K$ and 90 K, the mass flux increases by a factor of 3 with increasing the gravity acceleration from $1g_0$ up to $10g_0$. On the other hand, for ${\Delta}T=30\;K$, the flux is increased by a factor of 1.36 for the range of $1g_0{\leq}g{\leq}10g_0$. The maximum growth rates for $1g_0$, $4g_0$, $10g_0$ appear approximately in the neighborhood of y = 0.5, and the growth rates shows asymmetrical patterns, which indicate the occurrence of either one single or more than one convective cell. The maximum growth rate for $10g_0$ is nearly greater than that for $1g_0$ by a factor of 2.0 at $P_B=20\;Torr$. For three different gravity levels of $1g_0$, $4g_0$ and $10g_0$, the maximum growth rates are greater than the minimum rates by a factor of nearly 3.0, based on $P_B=20\;Torr$. The mass flux increases with increasing the gravity acceleration, for $1g_0{\leq}g_y{\leq}10g_0$, and decreases with increasing the partial pressure of component B, xenon (Xe), $P_B$. The $|U|_{max}$ is directly proportional to the gravity acceleration for $20\;Torr{\leq}P_B{\leq}300\;Torr$. As the partial pressure of $P_B$ (Torr) decreases from 300 Torr to 20 Torr, the slopes of the $|U|_{max}s$ versus the gravity accelerations increase from 0.1 sec to 0.17 sec. The mass flux of $Hg_2Cl_2$ is exponentially decayed with increasing the partial pressure of component B, $P_B$ (Torr) from 20 Torr up to 300 Torr.

Effects of thermal boundary conditions and microgravity environments on physical vapor transport of $Hg_2Cl_2-Xe$ system

Kim, Geug-Tae,Kwon, Moo-Hyun,Lee, Kyong-Hwan The Korea Association of Crystal Growth 2009 韓國結晶成長學會誌 Vol.19 No.4

For the effects of the nonlinear temperature profiles and reduced-gravity conditions we conduct a two-dimensional numerical modeling and simulations on the physical vapor transport processes of $Hg_2Cl_2-Xe$ system in the horizontal orientation position. Our results reveal that: (1) A decrease in aspect ratio from 5 to 2 leads to an increasingly nonuniform interfacial distribution and enhances the growth rate by one-order magnitude for normal gravity and linear wall temperature conditions. (2) Increasing the molecular weight of component B, Xenon results in a reduction in the effect of solutal convection. (3) The effect of aspect ratio affects the interfacial growth rates significantly under normal gravity condition rather than under reduced gravitational environments. (4) The transition from the convection-dominated regime to the diffusion-dominated regime ranges arises near at 0.1g$_0$ for operation conditions under consideration in this study.

Effect of Galhwahyejung-tang (GHT) on Alcohol-induced Oxidative Stress in Rats

Kim, Dong-Gyu,Kim, Tae-Hwan,Park, Sang-Eun,Kim, Hyung-Geug,Son, Chang-Gue,Hong, Sang-Hoon The Society of Korean Medicine 2010 대한한의학회지 Vol.31 No.6

Objectives: This study was aimed to investigate the effects of Galhwahyejung-tang (GHT) on alcohol-induced oxidative stress in rat model. Methods: Twenty SD rats were orally administrated with 40% ethanol (mL/kg) combined with GHT (50, 100, 200mg/kg) or distilled water for 2 weeks. Biochemistry in blood, malondialdehyde (MDA), total reactive oxygen species (ROS), and total antioxidant capacity (TAC) in serum, liver, brain, and kidney were determined. Results: GHT treatment significantly ameliorated the alcohol-induced alteration of hepatic enzyme; especially AST and ALT. GHT treatment also ameliorated the increase of MDA in liver, ROS level in serum and brain. GHT treatment reduced the depletion of antioxidant capacity in serum and brain. Conclusion: These results that GHT has antioxidant properties explaining the relevance of clinical application and its partial mechanisms of GHT.

Influence of thermo-physical properties on solutal convection by physical vapor transport of Hg₂Cl₂-N₂ system: Part I - solutal convection

Kim, Geug-Tae,Kim, Young-Joo The Korea Association of Crystal Growth 2010 韓國結晶成長學會誌 Vol.20 No.3

For typical governing dimensionless parameters of Ar = 5, Pr = 1.16, Le = 0.14, Pe = 3.57, Cv = 1.02, $Gr_s=2.65{\times}10^6$, the effects of thermo physical properties such as a molecular weight, a binary diffusivity coefficient, a partial pressure of component B on solutally buoyancy-driven convection (solutal Grashof number $Gr_s=2.65{\times}10^6$) are theoretically investigated for further understanding and insight into an essence of solutal convection occurring in the vapor phase during the physical vapor transport of a $Hg_2Cl_2-N_2$ system. The solutally buoyancy-driven convection is significantly affected by any significant disparity in the molecular weight of the crystal components and the impurity gas of nitrogen. The solutal convection in a vertical orientation is found to be more suppressed than a tenth reduction of gravitational accelerations in a horizontal orientation. For crystal growth parameters under consideration, the greater uniformity in the growth rate is obtained for either solutal convection mode in a vertical orientation or thermal convection mode in horizontal geometry. The growth rate is also found to be first order exponentially decayed for $10{\leq}P_B{\leq}200$ Torr.

Studies on Nusselt and Sherwood number for diffusion-advective convection during physical vapor transport of Hg₂Br₂

Kim, Geug Tae,Kwon, Moo Hyun The Korea Association of Crystal Growth 2021 韓國結晶成長學會誌 Vol.31 No.3

This paper is dedicated to numerical simulation for diffusion-advective convection in a square cavity during physical vapor transport of Hg₂Br₂. Flow characteristics of the temperature difference between the source and crystal regions, 50℃ (300℃ → 250℃), partial pressures of component argon of 20 Torr and 100 Torr are investigated and presented as velocity vectors and streamlines, isotherms and iso-mass concentrations contours. Moreover, alterations of average Nusselt and average Sherwood numbers with (a) the source and crystal regions, (b) the pressures of component argon of 20 Torr and 100 Torr are analyzed and addressed in details. Both average Nusselt and average Sherwood numbers are seen to decrease with the increasing values of the partial pressures of component argon. Also, it is found that for the two different partial pressures of component argon, average Nusselt numbers at the source region are greater than at the crystal region, and inversely, average Sherwood numbers at the crystal region are greater than the source region by a factor of 3.

Growth and characterization of lead bromide: application to mercurous bromide

Kim, Geug-Tae The Korea Association of Crystal Growth 2004 한국결정성장학회지 Vol.14 No.2

Mercurous Bromide ($Hg_2Br_2$) crystals hold promise for many acousto-optic and opto-electronic applications. This material is prepared in closed ampoules by the physical vapor transport (PVT) growth method. We investigate the effects of solutal convection on the crystal growth rate in a horizontal configuration for diffusive-convection conditions and purely diffusion conditions achievable in a low gravity environment. Our results show that the growth rate is decreased by a factor of one-fourth with a ten reduction of gravitational acceleration near y = 2.0 cm. For 0.1 $g_O$ the growth rate pattern exhibits relatively flat which is intimately related to diffusion-dominated processes. The growth rate nonuniformity is regardless of aspect ratio across the interfacial positions from 0 to 1.5. Also, the effect of a factor of the ten reduction in the gravitational acceleration is same to both Ar = 5 and 2. The enlargement in the molecular weight of B from 50 to 500 by a factor 4 causes a decrease in the maximum growth rate by the same factor, indicative of the effect of solutal gradients.

Predictions of zinc selenide single crystal growth rate for the micro gravity experiments

Kim, Geug-Tae The Korea Association of Crystal Growth 2004 한국결정성장학회지 Vol.14 No.5

One predicts the crystal growth rate of ZnSe with a low vapor pressure system in a horizontal configuration based on one dimensional advection-diffusion and two-dimensional diffusion-convection model. The present results show that for the ratios of partial pressures, s = 0.2 and 2.9, the growth rate increases with the temperature differences between the source and crystal. As the ratio of partial pressure approaches the stoichiometric value, s = 2 from s = 1.5 (zinc-deficient case: s < 2) and 2.9 (zinc-rich case: s > 2), the rate increases sharply. For the ranges from 1.5 to 1.999 (zinc-deficient case: s < 2) and from s = 9 to 2.9 (zinc-rich case: s > 2), the rate are slightly varied. From the viewpoint of the order of magnitude, the one-dimensional model for low vapor pressure system falls within the 2D predictions, which indicates the flow fields would be advective-diffusive. For the effects of gravitational accelerations on the rate, the gravitational constants are varied from 1 g to $10^{-6}$ g for $\Delta$T = 50 K and s = 1.5, the rates remain nearly constant, i.e., 211 mg/hr, which indicates Stefan flow is dominant over convection.

Convective heat and mass transfer affected by aspect ratios for physical vapor transport crystal growth in two dimensional rectangular enclosures

Kim, Geug Tae,Kwon, Moo Hyun The Korea Association of Crystal Growth 2018 한국결정성장학회지 Vol.28 No.2

Natural convection of a two dimensional laminar steady-state incompressible fluid flow in a rectangular enclosure has been investigated numerically for low aspect ratios with the physical vapor transport crystal growth. Results show that for aspect ratio (Ar = L/H) range of $0.1{\leq}Ar{\leq}1.5$, with the increase in Grashof number by one order of magnitude, the total mass flux is much augmented, and is exponentially decayed with the aspect ratio. Velocity and temperature profiles are presented at the mid-width of the rectangular enclosure. It is found that the effect of Grashof number on mass transfer is less significant when the enclosure is shallow (Ar = 0.1) and the influence of aspect ratio is stranger when the enclosure is tall and the Grashof number is high. Therefore, the convective phenomena are greatly affected by the variation of aspect ratios.