• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.73-79
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• 2022

In this study, a reaction study between Ga, which has recently been spotlighted as a low-temperature bonding material, and Cu, a representative electrode material, was conducted to investigate information necessary for low-temperature soldering applications. Interfacial reaction and intermetallic compound (IMC) growth were observed and analyzed by reacting Ga and Cu/Au substrates in the temperature range of 80-200℃. The main IMC growing at the reaction interface was CuGa₂ phase, and AuGa₂ IMC with small particle sizes was formed on the upper part and Cu₉Ga₄ IMC with a thin band shape on the lower part of the CuGa₂ layer. CuGa₂ particles showed a scallop shape, and the particle size increased without significant shape change as the reaction time increased, similar to the case of Cu₆Sn₅ growth. As a result of analyzing the CuGa₂ growth mechanism, the time exponent was calculated to be ~3.0 in the temperature range of 120-200℃, and the activation energy was measured to be 17.7 kJ/mol.

• New & Renewable Energy
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• v.18 no.1
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• pp.29-34
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• 2022

The most prevalent cause of solar cell efficiency loss is reduced recombination at the metal electrode and silicon junction. To boost efficiency, a a SiO_X/poly-Si passivating interface is being developed. Poly-Si for passivating contact is formed by various deposition methods (sputtering, PECVD, LPCVD, HWCVD) where the ploy-Si characterization depends on the deposition method. The sputtering process forms a dense Si film at a low deposition rate of 2.6 nm/min and develops a low passivation characteristic of 690 mV. The PECVD process offers a deposition rate of 28 nm/min with satisfactory passivation characteristics. The LPCVD process is the slowest with a deposition rate of 1.4 nm/min, and can prevent blistering if deposited at high temperatures. The HWCVD process has the fastest deposition rate at 150 nm/min with excellent passivation characteristics. However, the uniformity of the deposited film decreases as the area increases. Also, the best passivation characteristics are obtained at high doping. Thus, it is necessary to optimize the doping process depending on the deposition method.

• Advances in nano research
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• v.15 no.1
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• pp.1-13
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• 2023

Ti₃C₂T_x MXene, a 2D material, is known to exhibit unique characteristics that are strongly dependent on surface termination groups. Here, we developed a novel annealing approach with Ca as a reducing agent to simultaneously remove F and O groups from the surface of multilayered MXene powder. Unlike H₂ annealing that removes F effectively but has difficulty in removing O, annealing with Ca effectively removed both O and F. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy revealed that the proposed approach effectively removed F and O from the MXene powder. The results of O/N analyses showed that the O concentration decreased by 57.5% (from 2.66 to 1.13 wt%). In addition, XPS fitting showed that the volume fraction of metal oxides (TiO₂ and Al₂O₃) decreased, while surface termination groups (-O and -OH) were enhanced, which could increase the hydrophilic and adsorption properties of the MXene. These findings suggest that when F and O are removed from the MXene powder, the interlayer spacing of its lattice structure increases. The proposed treatment also resulted in an increase in the specific surface area (from 5.17 to 10.98 m²/g), with an increase in oxidation resistance temperature in air from ~436 to ~667 ℃. The benefits of this novel technology were verified by demonstrating the significantly improved cyclic charge-discharge characteristics of a lithium-ion battery with a Ca-treated MXene electrode.

• Journal of Electrochemical Science and Technology
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• v.15 no.1
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• pp.198-206
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• 2024

Given the high theoretical capacity (1,675 mAh g^-1) and the inherent affordability and ubiquity of elemental sulfur, it stands out as a prominent cathode material for advanced lithium metal batteries. Traditionally, sulfur was sequestered within conductive porous carbons, rooted in the understanding that their inherent conductivity could offset sulfur's non-conductive nature. This study, however, pivots toward a transformative approach by utilizing diatom shell (DS, diatomite)-a naturally abundant and economically viable siliceous mineral-as a sulfur host. This approach enabled the development of a sulfurlayered diatomite/S composite (DS/S) for cathodic applications. Even in the face of the insulating nature of both diatomite and sulfur, the DS/S composite displayed vigorous participation in the electrochemical conversion process. Furthermore, this composite substantially curbed the loss of soluble polysulfides and minimized structural wear during cycling. As a testament to its efficacy, our Li-S battery, integrating this composite, exhibited an excellent cycling performance: a specific capacity of 732 mAh g^-1 after 100 cycles and a robust 77% capacity retention. These findings challenge the erstwhile conviction of requiring a conductive host for sulfur. Owing to diatomite's hierarchical porous architecture, eco-friendliness, and accessibility, the DS/S electrode boasts optimal sulfur utilization, elevated specific capacity, enhanced rate capabilities at intensified C rates, and steadfast cycling stability that underscore its vast commercial promise.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.4
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• pp.120-129
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• 2003

The anodic alumina is synthesized using 0.3M oxalic acid and the barrier layers of the anodic alumina are removed using the 20wt% $H_2SO_4$ solution. The structure of the anodic alumina is analyzed by XRD and SEM. It is observed by SEM that the size of anodic alumina pore is about 60nm. And the uniformity of the anodic alumina surface under the 20wt% $H_2SO_4$ solution is poorer than the unifomity of the the normal anodic alumina surface. The anodic alumina and the carbon are used cathode and anode in$Cd(NO_3)_2{\cdot}4H_2O$, $Co(NO_3)_2{\cdot}6H_2O$ and $PbSO_4$ solutions. In this study, the constant D.C. electrical current is flowed in each solution for 24hours. It is found that the voltages so far as 4.6, 3.4 and 5.1V at $Cd(NO_3)_2{\cdot}4H_2O$, $Co(NO_3)_2{\cdot}6H_2O$ and $PbSO_4$ solutions increase with increasing the flowing current time and after the voltage does not change which values are 4.2, 2.7 and 2.4V, respectively. The amount of metal ions in solutions decrease with increasing the flowing current time until the flowing current time is 18hours and the metals are formed at the surface of anodic alumina. After the metal ions are removed using the anodic alumina, and $Cd^{2+}$, $Co^{2+}$ and $Pb^{2+}$ ions are removed again using flow cell with retriculate vitreous carbon(RVC) working electrode. The concentration of $Cd^{2+}$, and $Co^{2+}$ions decrease until the flowing time of the solutions is 20minutes and the concentration of $Pb^{2+}$ ion decreases until that time is 30minutes. In this case, the removal effects of $Cd^{2+}$, $Co^{2+}$ and $Pb^{2+}$ ions are 34.78, 28.79 and 86.38%, respectively. And it is possible that both $Cd^{2+}$ and $Co^{2+}$ions are adsorbed in pore of RVC at the same time and the removal effects of $Cd^{2+}$ and $Co^{2+}$ions are 32.30 and 31.37%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.599-604
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• 1998

We have investigated Pt and $RuO_2$ as a bottom electrode for ferroelectric capacitor applications. The bottom electrodes were prepared by using an RF magnetron sputtering method. Some of the investigated parameters were a substrate temperature, gas flow rate, RF power for the film growth, and post annealing effect. The substrate temperature strongly influenced the surface morphology and resistivity of the bottom electrodes as well as the film crystallographic structure. XRD results on Pt films showed a mixed phase of (111) and (200) peak for the substrate temperature ranged from RT to $200^{\circ}C$, and a preferred (111) orientation for $300^{\circ}C$. From the XRD and AFM results, we recommend the substrate temperature of $300^{\circ}C$ and RF power 80W for the Pt bottom electrode growth. With the variation of an oxygen partial pressure from 0 to 50%, we learned that only Ru metal was grown with 0~5% of $O_2$ gas, mixed phase of Ru and $RuO_2$ for $O_ 2$ partial pressure between 10~40%, and a pure $RuO_2$ phase with $O_2$ partial pressure of 50%. This result indicates that a double layer of $RuO_2/Ru$ can be grown in a process with the modulation of gas flow rate. Double layer structure is expected to reduce the fatigue problem while keeping a low electrical resistivity. As post anneal temperature was increased from RT to $700^{\circ}C$, the resistivity of Pt and $RuO_2$ was decreased linearly. This paper presents the optimized process conditions of the bottom electrodes for memory device applications.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.80-86
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• 2016

High Ni content layered oxide materials for the positive electrode in lithium-ion batteries have high specific capacity. However, their poor electrochemical and thermal stability at elevated temperature restrict the practical use. A small amount of $Al_2O_3$ was added to the mixture of transition metal hydroxide and lithium hydroxide. The $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ was simultaneously doped and coated with $Al_2O_3$ during heat-treatment. Electrochemical characteristics of modified $LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$ were evaluated by the galvanostatic cycling and the LSTA(linear sweep thermmametry) at the constant voltage conditions. The nano-sized $Al_2O_3$ added materials show better cycle performance at elevated temperature than that of micro-sized $Al_2O_3$. As the added amount of nano-$Al_2O_3$ increased, the thermal stability of electrode also enhanced, but the use of 2.5 mol% Al showed the best high temperature performance.

• Journal of the Korean Electrochemical Society
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• v.10 no.2
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• pp.132-140
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• 2007

The phase-shift method and correlation constants for studying a linear relationship between the behavior ($-{\varphi}\;vs.\;E$) of the phase shift ($0^{\circ}{\leq}-{\varphi}{\leq}90^{\circ}$) for the optimum intermediate frequency and that (${\theta}\;vs.\;E$) of the fractional surface coverage ($1{\geq}\theta{\geq}0$) have been proposed and verified to determine the Langmuir, Frumkin, and Temkin adsorption isotherms (${\theta}\;vs.\;E$) at noble metal/aqueous electrolyte interfaces. At an Ir/0.1 M KOH aqueous electrolyte interface, the Langmuir and Temkin adsorption isotherms (${\theta}\;vs.\;E$), equilibrium constants ($K=3.3{\times}10^{-4}\;mol^{-1}$ for the Langmuir and $K=3.3{\times}10^{-3}{\exp}(-4.6{\theta})\;mol^{-1}$ for the Temkin adsorption isotherm), interaction parameter (g = 4.6 for the Temkin adsorption isotherm), and standard free energies (${\Delta}G_{ads}^0=19.9kJ\;mol^{-1}\;for\;K=3.3{\times}10^{-4}\;mol^{-1}$ and $16.5<{\Delta}G_{\theta}^0<23.3\;kJ\;mol^{-1}\;for\;K=3.3{\times}10^{-3}{\exp}(-4.6{\theta})\;mol^{-1}\;and\;0.2<\theta<0.8$) of H for the cathodic $H_2$ evolution reaction are determined using the phase-shift method and correlation constants. The inhomogeneous and lateral interaction effects on the adsorption of H are negligible. At the intermediate values of ${\theta},\;i.e,\;0.2<{\theta}<0.8$, the Temkin adsorption isotherm (${\theta}\;vs.\;E$) correlating with the Langmuir or the Frumkin adsorption isotherm (${\theta}\;vs.\;E$), and vice versa, is readily determined using the correlation constants. The phase-shift method and correlation constants are accurate and reliable techniques to determine the adsorption isotherms (${\theta}\;vs.\;E$) and related electrode kinetic and thermodynamic parameters(K, g, ${\Delta}G_{ads}^0, {\Delta}G_{\theta}^0$).

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.4
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• pp.202-208
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• 2001

In Recent results suggested that doping $Ta_2O_5$ with a small amount of $TiO_2$ using standard ceramic processing techniques can increase the dielectric constant of $Ta_2O_5$ significantly. In this paper, this concept is studied using RTCVD (Rapid Thermal Chemical Vapor Deposition). Ti-doped $Ta_2O_5$ films are deposited using $TaC_{12}H_{30}O_5N$, $C_8H_{24}N_4Ti$, and $O_2$ on both Si and $NH_3$-nitrided Si substrates. An $NH_3$-based interface layer at the Si surface is used to prevent interfacial oxidation during the CVD process and post deposition annealing is performed in $H_2/O_2$ ambient to improve film quality and reduce leakage current. A sputtered TiN layer is used as a diffusion barrier between the Al gate electrode and the $TaTi_xO_y$ dielectric. XPS analyses confirm the formation of a ($Ta_2O_5)_{1-x}(TiO_2)_x$ composite oxide. A high quality $TaTi_xO_y$ gate stack with EOT (Equivalent Oxide Thickness) of $7{\AA}$ and leakage current $Jg=O.5A/textrm{cm}^2$ @ Vg=-1.0V has been achieved. We have also succeeded in forming a $TaTi_x/O_y$ composite oxide by rapid thermal oxidation of the as-deposited CVD TaTi films. The electrical properties and Jg-EOT characteristics of these composite oxides are remarkably similar to that of RTCVD $Ta_2O_5, suggesting that the dielectric constant of $Ta_2O_5$ is not affected by the addition of $TiO_2$.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.188.2-188.2
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• 2015

The presence of the conduction interface in epitaxial $LaAlO_3/SrTiO_3$ thin films has opened up challenging applications which can be expanded to next-generation nano-electronics. The metallic conduction path is associated with two adjacent insulating materials. Such device structure is applicable to frequency-dependent impedance spectroscopy. Impedance spectroscopy allows for simultaneous measurement of resistivity and dielectric constants, systematic identification of the underlying electrical origins, and the estimation of the electrical homogeneity in the corresponding electrical origins. Such unique capability is combined with the intentional control on the interface composition composed of $SrTiO_3$ and $CaTiO_3$, which can be denoted by $SrxCa1-_xTiO_3$. The underlying $Sr_xCa1-_xTiO_3$ interface was deposited using pulsed-laser deposition, followed by the epitaxial $LaAlO_3$ thin films. The platinum electrodes were constructed using metal shadow masks, in order to accommodate 2-point electrode configuration. Impedance spectroscopy was performed as the function of the relative ratio of Sr to Ca. The respective impedance spectra were analyzed in terms of the equivalent circuit models. Furthermore, the impedance spectra were monitored as a function of temperature. The ac-based characterization in the 2-dimensional conduction path supplements the dc-based electrical analysis. The artificial manipulation of the interface composition will be discussed towards the electrical application of 2-dimensional materials to the semiconductor devices in replacement for the current Si-based devices.