• Journal of the Korean Crystal Growth and Crystal Technology
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• 제7권1호
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• pp.143-150
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• 1997

The electrical properties of polysilicon thin films implanted with $B_2H_6$ diluted in $H_2$ as dopant source using ion mass doping technique and the effect of radiation damage on the dopant activation behavior were investigated. Comparing the SIMS profiles of boron in polysilicon films with that obtained from computer simulation using TRIM92 the most probable ion species were $B_2H_x\;^+$(x＝1, 2, 3‥‥) type molecular ions. As a result of the Implantation of energetic massive ions, a continuous amorphized layer was created in polysilicon films where the fraction of amorphized layer varied with doping time. This amorphization comes from the fact that mass separation of implanting species is not employed in this ion mass doping technique. In the dopant activation behavior, reverse annealing phenomenon appeared in the intermediate annealing temperature range for a severely damaged specimen. The experimental result showed that the off-state current of the p-channel polysilicon thin film transistor is dependent on the degree of radiation damage.

• Progress in Superconductivity
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• 제9권1호
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• pp.80-84
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• 2007

Charcoal was used as a carbon source for improving the critical current density of $MgB_2$ and the effect of annealing temperature on the $J_c$ of $MgB_2$ was investigated. The charcoal powder used in this study was $1{\sim}2$ microns in size and was prepared by wet attrition milling. $MgB_2$ bulk samples with a nominal composition of $Mg(B_{0.95}C_{0.05})_2$ were prepared by in situ process of Mg and B powders. The powder mixture was uniaxially compacted into pellets and heat treated at temperatures of $650^{\circ}C\;-\;1000^{\circ}C$ for 30 minutes in flowing Ar gas. It was found that superconducting transition temperature of $Mg(B_{0.95}C_{0.05})_2$ decreased by charcoal additions which indicates the carbon substitution for boron site. $J_c$ of $Mg(B_{0.95}C_{0.05})_2$ was lower than that of the undoped $MgB_2$ at the magnetic fields smaller than 4 Tesla, while it was higher than that of the undoped sample especially at the magnetic field higher than 4 T. High temperature annealing seems to be effective in increasing $J_c$ due to the enhanced carbon diffusion into boron sites.

• Journal of the Korean Solar Energy Society
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• 제30권6호
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• pp.16-21
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• 2010

It is well-known that Boron-doped Cz Si solar cells suffer light-induced degradation due to boron-oxygen defect which is responsible of a reduction in lifetime and hence efficiency. In this paper, we assume that PV solar cell has been connected with variable load to account the real operating condition and it shows different light-induced degradation of Si solar cell. To evaluate the effect of light-induced degradation for solar cell with various load, Single crystalline solar cells are connected with open and short circuits during light exposure. Isc-Voc curve evaluate light induced degradation of solar cells and the reason is explained as a change for serial resistance. From the results, Electrical characteristics of solar cells show better performance under short circuit conditions, after light exposure.

• Membrane Journal
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• 제21권4호
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• pp.345-350
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• 2011

No investigation has yet been accomplished to screen the boron-doped effects on vanadium based metal membranes. The synthesis, hydrogen permeation properties and chemical stability of a novel Pd-coated $V_{99.8}B_{0.2}$ alloy membrane are presented in this report. Hydrogen permeation experiments have been performed to investigate the hydrogen transport properties through the Pd-coated $V_{99.8}B_{0.2}$ alloy membrane in the absolute pressure range 1.0~3.0 bar under pure hydrogen, hydrogen-carbon dioxide gas mixture at $400^{\circ}C$. The maximum hydrogen permeation flux was $48.5mL/min/cm^2$ for a 0.5 mm thick membrane under pure hydrogen. This results offer new direction in the synthesis of novel non-Palladium-based metal membranes for hydrogen separation in water-gas shift reaction.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.251-251
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• 2016

For several decades, industrial processes consume a huge amount of raw water for various objects that consequently results in the generation of large amounts of wastewater. Wastewaters are consisting of complex mixture of different inorganic and organic compounds and some of them can be toxic, hazardous and hard to degrade. These effluents are mainly treated by conventional technologies such are aerobic and anaerobic treatment and chemical coagulation. But, these processes are not suitable for eliminating all hazardous chemical compounds form wastewater and generate a large amount of toxic sludge. Therefore, other processes have been studied and applied together with these techniques to enhance purification results. These include photocatalysis, absorption, advanced oxidation processes, and ozonation, but also have their own drawbacks. In recent years, electrochemical techniques have received attention as wastewater treatment process that could be show higher purification results. Among them, boron doped diamond (BDD) attract attention as electrochemical electrode due to good chemical and electrochemical stability, long lifetime and wide potential window that necessary properties for anode electrode. So, there are many researches about high quality BDD on Nb, Ta, W and Si substrates, but, their application in effluents treatment is not suitable due to high cost of metal and low conductivity of Si. To solve these problems, Ti has been candidate as substrate in consideration of cost and property. But there are adhesion issues that must be overcome to apply Ti as BDD substrate. Al, Cu, Ti and Nb thin films were deposited on Ti substrate to improve adhesion between substrate and BDD thin film. In this paper, BDD films were deposited by hot filament chemical vapor deposition (HF-CVD) method. Prior to deposition, cleaning processes were conducted in acetone, ethanol, and isopropyl alcohol (IPA) using sonification machine for 7 min, respectively. And metal layer with the thickness of 200 nm were deposited by DC magnetron sputtering (DCMS). To analyze microstructure X-ray diffraction (XRD, Bruker gads) and field emission scanning electron microscopy (FE-SEM, Hitachi) were used. It is confirmed that metal layer was effective to adhesion property and improved electrode property. Electrochemical measurements were carried out in a three electrode electrochemical cell containing a 0.5 % H2SO4 in deionized water. As a result, it is confirmed that metal inter layer heavily effect on BDD property by improving adhesion property due to suppressing formation of titanium carbide.

• Journal of the Korean Vacuum Society
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• 제16권2호
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• pp.99-104
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• 2007

Porous silicon exhibiting dual optical properties, both $Febry-P{\acute{e}}rot$ fringe (optical reflectivity) and photoluminescence had been developed and used as chemical sensors. Porous silicon samples were prepared by an electrochemical etch of p-type silicon wafer (boron-doped, <100> orientation, resistivity ; $1-10{\Omega}cm$). Two different types of porous silicon, fresh porous silicon (Si-H terminated) and oxidized porous silicon (Si-OH terminated)by the thermal oxidation, were prepared. Then the samples were exposed to the vapor of various organics, such as methanol, acetone, hexane, and toluene. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organic vapors for sensing VOC's. These surface-modified samples showed unique respond in both reflectivity and photoluminescence with various organic vapors. While polar molecules exhibit greater quenching photoluminescence, molecules having higher vapor pressure show greater red shift for reflectivity.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.289-289
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• 2013

While there are plenty of studies on synthesizing semiconducting germanium nanowires (Ge NWs) by vapor-liquid-solid (VLS) process, it is difficult to inject dopants into them with uniform dopants distribution due to vapor-solid (VS) deposition. In particular, as precursors and dopants such as germane ($GeH_4$), phosphine ($PH_3$) or diborane ($B_2H_6$) incorporate through sidewall of nanowire, it is hard to obtain the structural and electrical uniformity of Ge NWs. Moreover, the drastic tapered structure of Ge NWs is observed when it is synthesized at high temperature over $400^{\circ}C$ because of excessive VS deposition. In 2006, Emanuel Tutuc et al. demonstrated Ge NW pn junction using p-type shell as depleted layer. However, it could not be prevented from undesirable VS deposition and it still kept the tapered structures of Ge NWs as a result. Herein, we adopt $C_2H_2$ gas in order to passivate Ge NWs with carbon sheath, which makes the entire Ge NWs uniform at even higher temperature over $450^{\circ}C$. We can also synthesize non-tapered and uniformly doped Ge NWs, restricting incorporation of excess germanium on the surface. The Ge NWs with carbon sheath are grown via VLS process on a $Si/SiO_2$ substrate coated 2 nm Au film. Thin Au film is thermally evaporated on a $Si/SiO_2$ substrate. The NW is grown flowing $GeH_4$, HCl, $C_2H_2$ and PH3 for n-type, $B_2H_6$ for p-type at a total pressure of 15 Torr and temperatures of $480{\sim}500^{\circ}C$. Scanning electron microscopy (SEM) reveals clear surface of the Ge NWs synthesized at $500^{\circ}C$. Raman spectroscopy peaked at about ~300 $cm^{-1}$ indicates it is comprised of single crystalline germanium in the core of Ge NWs and it is proved to be covered by thin amorphous carbon by two peaks of 1330 $cm^{-1}$ (D-band) and 1590 $cm^{-1}$ (G-band). Furthermore, the electrical performances of Ge NWs doped with boron and phosphorus are measured by field effect transistor (FET) and they shows typical curves of p-type and n-type FET. It is expected to have general potentials for development of logic devices and solar cells using p-type and n-type Ge NWs with carbon sheath.

• Journal of the Korean Vacuum Society
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• 제16권3호
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• pp.221-226
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• 2007

DBR (distributed Bragg reflectors) PSi (porous silicon) composite films displaying dual optical properties, both optical reflectivity and photoluminescence had been developed. DBR PSi samples were prepared by electrochemical etch of heavily doped $p^{++}-type$ silicon wafers (boron doped, polished on the <100> face, resistivity of $0.8-1.2m{\Omega}-cm$, Siltronix, Inc.). Free-standing DBR PSi films were treated with PMMA (polymethyl methacrylate) to produce flexible, stable composite materials in which the PSi matrix is covered with PMMA containing photoluminescent polysiloles. Optical characteristics of DBR PSi/polysilole-impregnated PMMA composite materials exhibit both their photonic reflectivity at 565 nm and photoluminescence at 510 nm, simultaneously. A possible application of this materials will be discussed.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.112.1-112.1
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• 2011

The back contact solar cell (BCSC) has several advantages compared to the conventional solar cell since it can reduce grid shadowing loss and contact resistance between the electrode and the silicon substrate. This paper presents the effect of the surface texturing of the silicon BCSC by varying the texturing depth or the texturing gap in the commercially available simulation software, ATHENA and ATLAS of the company SILVACO. The texturing depth was varied from $5{\mu}m$ to $150{\mu}m$ and the texturing gap was varied from $1{\mu}m$ to $100{\mu}m$ in the simulation. The resulting efficiency of the silicon BCSC was evaluated depending on the texturing condition. The quantum efficiency and the I-V curve of the designed silicon BCSC was also obtained for the analysis since they are closely related with the solar cell efficiency. Other parameters of the simulated silicon BCSC are as follows. The substrate was an n-type silicon, which was doped with phosphorous at $6{\times}10^{15}cm^{-3}$, and its thickness was $180{\mu}m$, a typical thickness of commercial solar cell substrate thickness. The back surface field (BSF) was $1{\times}10^{20}\;cm^{-3}$ and the doping concentration of a boron doped emitter was $8.5{\times}10^{19}\;cm^{-3}$. The pitch of the silicon BCSC was $1250{\mu}m$ and the anti-reflection coating (ARC) SiN thickness was $0.079{\mu}m$. It was assumed that the texturing was anisotropic etching of crystalline silicon, resulting in texturing angle of 54.7 degrees. The best efficiency was 25.6264% when texturing depth was $50{\mu}m$ with zero texturing gap in case of low texturing depth (< $100{\mu}m$).

• Korean Journal of Materials Research
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• 제22권1호
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• pp.42-45
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• 2012

The mechanical behavior and microstructural evolution during high temperature tensile deformation of recrystallized Ni3Al polycrystals doped with boron were investigated as functions of initial grain size, tensile strain rate and temperature. In order to obtain more precise information on the deformation mechanism, tensile specimens were rapidly quenched immediately after deformation at a cooling rate of more than $2000Ks^{-1}$, and were then observed by transmission electron microscopy (TEM). Mechanical tests in the range of 923 K to 1012 K were carried out in a vacuum of less than $3{\times}10^{-4}$ Pa using an Instron-type machine with various but constant cross head speeds corresponding to the initial strain rates from $1.0{\times}10^{-4}$ to $3.1{\times}10^{-5}s^{-1}$. After heating to deformation temperature, the specimen was kept for more than 1.8 ks before testing. The following results were obtained: (1) Flow behavior was affected by initial strain size; with decreasing initial grain size, the level of a stress peak in the true stress-true strain curve decreased, the steady state region was enlarged and elongation increased. (2) On the basis of TEM observation of rapidly quenched specimens, it was confirmed that dynamic recrystallization certainly occurred on deformation of fine-grained ($3.3{\mu}m$) and intermediate-grained ($5.0{\mu}m$) specimens at an initial strain rate of $3.1{\times}10^{-5}s^{-1}$ and at 973 K. (3) There were some dislocation-free grains among the new recrystallized grains. The obtained results suggest that both dynamic recrystallization and grain boundary sliding are operative during high temperature deformation.