Computations on the Thermal Characteristics of SF and CO₂ Switching Arcs on a Microscopic Scale.

Pure sulfur hexafluoride is a colorless, odorless, non-toxic, inflammable, chemically inert and thermally stable gas and has proven its worth as an excellent interruption and dielectric medium. SF has been successfully used for interruption and insulation purposes as interrupters and circuit-breakers in gas-insulated substations. Due to its long lifetime and high global warming potential, this gas was put on the list of fluorinated greenhouse gases in the Kyoto Protocol aimed at controlling the emission of man-made greenhouse gases.

Selective Growth and Contact Gap-Fill of Low Resistivity Si via Microwave Plasma-Enhanced CVD.

Low resistivity polycrystalline Si could be selectively grown in the deep (~200 nm) and narrow patterns (~20 nm) of 20 nm pitch design rule DRAM (Dynamic Random Access Memory) by microwave plasma-enhanced chemical vapor deposition (MW-CVD). We were able to achieve the high phosphorus (CVD gap-fill in a large electrical contact area which does is affected by line pitch size) doping concentration (>2.5 × 10 cm) and, thus, a low resistivity by adjusting source gas (SiH, H, PH) decomposition through MW-CVD with a showerhead controlling the decomposition of source gases by using two different gas injection paths.

Thermomagnetic Convection of Ferrofluid in an Enclosure Channel with an Internal Magnetic Field.

Ferrofluid is a colloidal liquid in which magnetic nanoparticles such as FeO are dispersed in a nonconductive solution, and the average diameter of the nanoparticles is 10 nm. When a magnetic field is applied, the ferrofluid generates magnetization, which changes the physical properties of the fluid itself. In this study, characteristics of the thermomagnetic convection of ferrofluid (FeO) by the permanent magnet in the enclosure channel were studied.

Quasi-Three-Dimensional Computations of the Microscopic Thermal and Dielectric Characteristics of an SF Rotating Switching Arc.

Pure sulfur hexafluoride (SF) is chemically inert, non-flammable, non-toxic and thermally stable, and it has excellent dielectric strength and arc-quenching and control properties. The switching-off process of SF arc discharges occurs at the region between the contacts during the opening sequence to interrupt the flow of excessive current in a faulty network. The arc is tolerated in a controlled manner until a natural current zero when the arc discharge is rapidly quenched to restrict the thermal and dielectric reignition to the interruption.

Thermal-Flow Characteristics of Ferrofluids in a Rotating Eccentric Cylinder under External Magnetic Force.

Heat dissipation has become an important issue due to the miniaturization of various electronic devices. Various methods such as spray and nozzle coolers, heat sinks and so on are used for heat dissipation. However, the emergence of ferrofluids drastically improves the operating characteristics of electromagnetic systems and devices.

Two-Dimensional Computations on the Thermal Behaviors Between Arc Plasmas and Their Electrodes for the Switching Chamber Design.

A SF6 self-blast switching chamber belongs to a new generation of high-voltage switching devices, which take advantage of the auto-expansion principle and arc rotation to improve the switching performance on thermal and dielectric interruptions. The thermal behaviors between the arc plasma and the electrodes in the device are very complex to understand only through experimental studies. Since the late nineteen-eighties, significant progress has been made in computational methods describing the physical processes occurring in thermal plasmas.

Interaction Model Between an Electrical Arc and a Material for Arc Discharge Synthesis of Metal Nanoparticles.

Metal nanoparticles are used in applications ranging from bio-diagnostics to catalysis due to the expectation to improve attributes or the performance of specific products or processes. The electric arc can be used to produce metal nanoparticles by evaporating the anode and forming the anode vapor. In order to synthesize the nanoparticles of the desired properties, the influence of various input parameters on the growth kinetics has to be fully understood.

Structural Characteristics of a Conical-Frustum-Patterned Stretchable Heater in an External-Force Environment.

Stretchable heaters are mechanically and biomedically advantageous because they are more flexible than the conventional microheaters. To determine the way that a heater can be used appropriately in a wide range of application fields, studies on the mechanical and thermal characteristics regarding various film configurations are underway. In this study, the mechanical characteristics of conical-frustum-patterned stretchable heaters with various configurations with upper-radius (R1), bottom-radius (R2), and height (h) aspect ratios were numerically investigated when tensile forces and bending moments were applied to the film of heater.

Cesium lead iodide solar cells controlled by annealing temperature.

An inorganic lead halide perovskite film, CsPbI, used as an absorber in perovskite solar cells (PSCs) was optimized by controlling the annealing temperature and the layer thickness. The CsPbI layer was synthesized by one-step coating of CsI mixed with PbI and a HI additive in N,N-dimethylformamide. The annealing temperature of the CsPbI film was varied from 80 to 120 °C for different durations and the thickness was controlled by changing the spin-coating rpm.

Mogul-Patterned Elastomeric Substrate for Stretchable Electronics.

A mogul-patterned stretchable substrate with multidirectional stretchability and minimal fracture of layers under high stretching is fabricated by double photolithography and soft lithography. Au layers and a reduced graphene oxide chemiresistor on a mogul-patterned poly(dimethylsiloxane) substrate are stable and durable under various stretching conditions. The newly designed mogul-patterned stretchable substrate shows great promise for stretchable electronics.

Thermal Characteristics of Amorphous Indium-Gallium-Zinc-Oxide and Graphite in Display Panel Based Thin Film Transistors.

One of the important design factors in the smart electronic industry is proper heat treatment of the display panel. In order to improve the heat transfer performance of display panels, we analyzed a three-dimensional model of multi-stack layers of the thin film transistors (TFTs). In particular, we numerically investigated the thermal barrier effects of active layers having different material properties of a-IGZO (isotropy) and graphite (anisotropy).

Thermomagnetic Convective Flow Characteristics of Oil-Based Magnetic Nanofluids in Rectangular Enclosure.

The characteristics of thermomagnetic convective flow in a rectangular enclosure heated from below and filled with oil-based nanofluid (EFH-1, Ferrotec.), so called ferrofluid, were numerically investigated. The enclosure contained obstacles with rectangular or triangular configurations mounted on the top and bottom walls.

Temperature Prediction in a Free-Burning Arc and Electrodes for Nanostructured Materials and Systems.

Temperature in a free-burning arc used for synthesis of nanoparticles and nanostructured materials is generally around 20,000 K just below the cathode, falling to about 15,000 K just above the anode, and decreasing rapidly in the radial direction. Therefore, the electrode erosion is indispensable for these atmospheric plasma systems, as well as for switching devices, due to the high heat flux transferred from high temperature arcs to electrodes, but experimental and theoretical works have not identified the characteristic phenomena because of the complex physical processes. To the previous study, we have focused on the arc self-induced fluid flow in a free-burning arc using the computational fluid dynamics (CFD) technique.

Magnetophoresis Effects on the Flow Characteristics of Oil-Based Ferrofluids in Rectangular Enclosures.

This study numerically investigated the flow characteristics in a rectangular enclosure filled with oil-based ferrofluid (EFH-1, Ferrotec.) under the influence of external magnetic fields. The rectangular enclosure contained obstacles with different shapes, such as a rectangle and a triangle mounted on the top and bottom wall surfaces.

Effects of Mass Flow Rate on the Thermal-Flow Characteristics of Microwave CO2 Plasma.

In this study, the thermal-flow characteristics of atmospheric pressure microwave CO2 plasma were numerically investigated by simulation. The electric and gas flow fields in the reaction chamber with a microwave axial injection torch operated at 2.45 GHz were simulated.

Numerical Study on the Particle Trajectory Tracking in a Micro-UV Bio-Fluorescence Sensor.

A micro-UV bio-fluorescence sensor was developed to detect primary biological aerosols including bacteria, bacterial spores, fungal spores, pollens, viruses, algae, etc. In order to effectively detect the bio-particles in a micro-UV bio-fluorescence sensor, numerical calculations were performed to adjust for appropriate flow conditions of the sensor by regulating the sample aerosols and sheath flow. In particular, a CFD-based model of hydrodynamic processes was developed by computing the trajectory of particles using commercially available ANSYS CFX-14 software and the Lagrangian tracking model.

Effect of Al2O3 insulator thickness on the structural integrity of amorphous indium-gallium-zinc-oxide based thin film transistors.

The current transparent oxide semiconductors (TOSs) technology provides flexibility and high performance. In this study, multi-stack nano-layers of TOSs were designed for three-dimensional analysis of amorphous indium-gallium-zinc-oxide (a-IGZO) based thin film transistors (TFTs). In particular, the effects of torsional and compressive stresses on the nano-sized active layers such as the a-IGZO layer were investigated.

Micropatterning of TiO2 thin films by MOCVD and study of their growth tendency.

In this work, we studied the growth tendency of TiO2 thin films deposited on a narrow-stripe area (<10 μm). TiO2 thin films were selectively deposited on OTS patterned Si(100) substrates by MOCVD. The experimental data showed that the film growth tendency was divided into two behaviors above and below a line patterning width of 4 μm.

Effect of nozzle tip configuration on the micro-droplet formation.

Micro-droplet formation is an emerging area of research due to its wide-ranging applications in micro-fluidic based devices. For high resolution patterning and coating processes in various industrial fields, the formation of micro-droplets should be controlled according to the rheological properties of the working fluids. However, the physical properties of the some of working fluids are limited to meet the industrial applications.

Numerical study on the mixing performance of a ring-type electroosmotic micromixer with different obstacle configurations.

A new type of electrokinetic micromixer with a ring-type channel is introduced for fast mixing. The proposed mixer takes two fluids from different inlets and combines them in a ring-type mixing chamber. The fluids enter two different inlets (inner radius: 25 microm and outer radius: 50 microm), respectively.

Numerical analysis of the zeta potential regarding the characteristics of a ring-type electro-osmotic mixer.

The micromixer that is applied for the electro-osmotic effect in this study, which is a passive type, takes two fluids from different inlets and combines them into a single channel. The fluids then enter the mixing chamber with different inner and outer radii. Four microelectrodes are positioned on the outer wall of the mixing chamber.