• Current Photovoltaic Research
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• v.3 no.3
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• pp.85-90
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• 2015

Two-step processes for preparing $Cu(In,Ga)Se_2$ absorber layers consist of precursor layer formation and subsequent annealing in a Se-containing atmosphere. Among the various deposition methods for precursor layer, the nonvacuum (wet) processes have been spotlighted as alternatives to vacuum-based methods due to their potential to realize low-cost, scalable PV devices. However, due to its porous nature, the precursor layer deposited on Mo substrate by nonvacuum methods often suffers from thick $MoSe_2$ formation during selenization under a high Se vapor pressure. On the contrary, selenization under a low Se pressure to avoid $MoSe_2$ formation typically leads to low crystal quality of absorber films. Although TiN has been reported as a diffusion barrier against Se, the additional sputtering to deposit TiN layer may induce the complexity of fabrication process and nullify the advantages of nonvacuum deposition of absorber film. In this work, Mo oxide layers via thermal oxidation of Mo substrate have been explored as an alternative diffusion barrier. The morphology and phase evolution was examined as a function of oxidation temperature. The resulting Mo/Mo oxides double layers were employed as a back contact electrode for $CuInSe_2$ solar cells and were found to effectively suppress the formation of $MoSe_2$ layer.

• Analytical Science and Technology
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• v.8 no.3
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• pp.341-350
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• 1995

$Nd_{14}Fe_{80}B_6$ ribbon alloy was manufactured with using melt-spinning method and analyzed the magnetic properties according to the manufacturing conditions. The microstructure and magnetic properties of melt-spun ribbons are sensitively dependent on the quench rate and annealing conditions. As-quenched $Nd_{14}Fe_{80}B_6$ ribbons with optimum magnetic properties are obtained at wheel speed($v_s$) of about 20m/sec and over quenched ribbons show optimum magnetic properties at $v_s$=22m/see when annealed for 30 minutes at $600^{\circ}C$ under vacuum. The crystallization temperature($T_k$) of $Nd_2Fe_{14}B$ phase is about $595^{\circ}C$ in the DTA analysis.

• Journal of the Korean Ceramic Society
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• v.33 no.2
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• pp.149-154
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• 1996

ZnO and Al-doped ZnO thin films were prepared by sol-gel dip-coating method and electrical and optical properties of films were investigated. Using the zinc acetate dihydrate and acetylaceton(AcAc) as a chelating agent stable ZnO sol was synthesized with HCl catalyst. Adding aluminium chloride to the ZnO sol Al-doped ZnO sol could be also synthesized. As Al contents increase the crystallinity of ZnO thin film was retarded by increased compressive stress in the film resulted from the difference of ionic radius between Zn2+ and Al3+ The thickness of ZnO and Al-doped ZnO thin film was in the range of 2100~2350$\AA$. The resistivity of ZnO thin films was measured by Van der Pauw method. ZnO and Al-doped ZnO thin films with annealing temperature and Al content had the resistivity of 0.78~1.65$\Omega$cm and ZnO and Al-doped ZnO thin film post-annealed at 40$0^{\circ}C$ in vacuum(5$\times$10-5 torr) showed the resistivity of 2.28$\times$10-2$\Omega$cm. And the trans-mittance of ZnO and Al-doped ZnO thin film is in the range of 91-97% in visible range.

• Korean Journal of Materials Research
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• v.20 no.8
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• pp.401-407
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• 2010

We studied the influence of different types of metal electrodes on the performance of solution-processed zinc tin oxide (ZTO) thin-film transistors. The ZTO thin-film was obtained by spin-coating the sol-gel solution made from zinc acetate and tin acetate dissolved in 2-methoxyethanol. Various metals, Al, Au, Ag and Cu, were used to make contacts with the solution-deposited ZTO layers by selective deposition through a metal shadow mask. Contact resistance between the metal electrode and the semiconductor was obtained by a transmission line method (TLM). The device based on an Al electrode exhibited superior performance as compared to those based on other metals. Kelvin probe force microscopy (KPFM) allowed us to measure the work function of the oxide semiconductor to understand the variation of the device performance as a function of the types metal electrode. The solution-processed ZTO contained nanopores that resulted from the burnout of the organic species during the annealing. This different surface structure associated with the solution-processed ZTO gave a rise to a different work function value as compared to the vacuum-deposited counterpart. More oxygen could be adsorbed on the nanoporous solution-processed ZTO with large accessible surface areas, which increased its work function. This observation explained why the solution-processed ZTO makes an ohmic contact with the Al electrode.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.956-960
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• 1998

The interfacial reaction between the CoINb bilayer and the $SiO_2$ substrate in the temperature range of $330^{\circ}C$-$800^{\circ}C$ in a vacuum has been investigated by X-ray photoelectron spectroscopy, glancing angle XRD, Auger Electron Spectroscopy and Atomic force microscopy. The Co and Nb were actively interdiffused at $600^{\circ}C$, and the layer inversion completed at $700^{\circ}C$. NbO was formed by interfacial reaction between the Nb interlayer and the $SiO_2$ substrate, while $Nb_20_5$ was formed on the surface by reaction of Nb with oxygen in the ambients. Free Si atoms obtained by the reaction between Nb and $SiO_2$ formed silicides like CoSi and $Nb_5Si_3$ by reacting with Co and Nb remnants. The sheet resistance of the Co/Nb bilayer increased substantially after annealing at $800^{\circ}C$. which is due to the agglomeration of the Co layer to reduce its surface energy.

• Journal of Powder Materials
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• v.12 no.5 s.52
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• pp.357-361
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• 2005

Fe-doped skutterudite $CoSb_3$ with a nominal composition of $Fe_{x}Co_{4-x}Sb_{12}(0\;{\le}\;x\;{\le}\;2.5)$ has been synthesized by mechanical alloying (MA) of elemental powders, followed by hot pressing. Phase transformations during mechanical alloying and hot pressing were systematically investigated using XRD. Single phase skutterudite was successfully produced by vacuum hot pressing using as-milled powders without subsequent annealing. However, second phase in the form of marcasite structure $FeSb_2$ was found to exist in case of $x\;{\ge}\;2$, suggesting the solubility limit of Fe with Co in this system. Thermoelectric properties as functions of temperature and Fe contents were evaluated for the hot pressed specimens. Fe substitution up to x=1.5 with Co in $Fe_{x}Co_{4-x}Sb_{12}$ appeared to increase thermoelectric figure of merit (ZT) and the maximum ZT was found to be 0.78 at 525K in this study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.1
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• pp.37-42
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• 2000

Copper thin films have been prepared by a metal organic chemical vapor deposition (MOCVD) technology on polyimide and TiN substrates. The Cu-MOCVD technology has advantages of the high deposition rate and the good step coverage compared with the conventional physical vapor deposition (PVD) technology in several industrial applications. The Cu films have been deposited with varying the experimental conditions of substrate temperatures and copper source vapor pressures. The films were annealed in a vacuum condition after the deposition, and the annealing effect on the electrical properties of the films was measured. The crystallinity and the microstructures of the films were observed by scanning electron microscopy (SEM), and the electrical resistivity was measured by 4-point probe. In the case of the Cu deposition on TiN substrate, the best electrical property of the films was measured for the samples prepared at 18$0^{\circ}C$. Very high deposition rate of the Cu film up to 250 nm/min was obtained on the polyimide substrate when the mixture of liquid and vapour precursor was used.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.111-111
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• 2007

Further scaling the semiconductor devices down to low dozens of nanometer needs the extremely shallow depth in junction and the intentional counter-doping in the silicon gate. Conventional ion beam ion implantation has some disadvantages and limitations for the future applications. In order to solve them, therefore, plasma source ion implantation technique has been considered as a promising new method for the high throughputs at low energy and the fabrication of the ultra-shallow junctions. In this paper, we study about the effects of DC bias and base pressure as a process parameter. The diluted mixture gas (5% $PH_3/H_2$) was used as a precursor source and chamber is used for vacuum pressure conditions. After ion doping into the Si wafer(100), the samples were annealed via rapid thermal annealing, of which annealed temperature ranges above the $950^{\circ}C$. The junction depth, calculated at dose level of $1{\times}10^{18}/cm^3$, was measured by secondary ion mass spectroscopy(SIMS) and sheet resistance by contact and non-contact mode. Surface morphology of samples was analyzed by scanning electron microscopy. As a result, we could accomplish the process conditions better than in advance.

• Korean Journal of Materials Research
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• v.19 no.1
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• pp.33-36
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• 2009

Inorganic-organic composite thin-film-transistors (TFTs) of ZnO nanowire/Poly(3-hexylthiophene) (P3HT) were investigated by changing the nanowire densities inside the composites. Crystalline ZnO nanowires were synthesized via an aqueous solution method at a low temperature, and the nanowire densities inside the composites were controlled by changing the ultrasonifiaction time. The channel layers were prepared with composites by spin-coating at 2000 rpm, which was followed by annealing in a vacuum at $100^{\circ}C$ for 10 hours. Au/inorganic-organic composite layer/$SiO_2$ structures were fabricated and the mobility, $I_{on}/I_{off}$ ratio, and threshold voltage were then measured to analyze the electrical characteristics of the channel layer. Compared with a P3HT TFT, the electrical properties of TFT were found to be improved after increasing the nanowire density inside the composites. The mobility of the P3HT TFT was approximately $10^{-4}cm^2/V{\cdot}s$. However, the mobility of the ZnO nanowire/P3HT composite TFT was increased by two orders compared to that of the P3HT TFT. In terms of the $I_{on}/I_{off}$ ratio, the composite device showed a two-fold increase compared to that of the P3HT TFT.

• Korean Journal of Metals and Materials
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• v.48 no.4
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• pp.357-362
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• 2010

Ferromagnetic Mn-Al nanoparticles were prepared using a plasma arc discharge method. The influence of the process parameters on the vaporization rate, composition, particle size, and magnetic properties of the as-produced nanoparticles was investigated. The Mn content was found to be higher in the nanoparticles than in the corresponding mother materials, although the difference diminished with the reaction time. As the $H_2$ content in the reaction gas increased, both the vaporization rate and the particle size increased. With 30 at.% Mn, the average particle diameter was 35.2 nm under a pure Ar gas condition, whereas it was 95.4 nm at a Ar:$H_2$ ratio of 60:40. With the addition of a small amount of carbon, ${\varepsilon}$-phase nanoparticles were successfully synthesized. After a heat treatment in a vacuum for 30 min at $500^{\circ}C$, the nonmagnetic ${\varepsilon}$-phase was transformed into the ferromagnetic ${\tau}$-phase, and a very high coercivity of nearly 5.6 kOe was achieved.