• 연구논문집
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• s.34
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• pp.121-129
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• 2004

The influence of powder size and ball-milling time on the magnetic properties of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline alloy powder was investigated. Flake-shaped powders were produced by pulverizing the ribbons annealed at $550^\circC$ for 1 hour. The powders were classified and consolidated into core shapes at a pressure of 18ton/$cm^2$. The initial permeability at 100kHz of the inductor core produced using $53-75\mum$ powders showed the highest value although its consolidated density showed the lowest one. The reason for the result is due to the cracking of the particles larger than $75\mum$ during the consolidation process. The ball-milling of powders for 2-4 hours improved the consolidation density and the initial permeability of the cores. The intrinsic coercivity of the powder decreased as well, resulting from the stress relief of the powder by a short-time milling.

• Journal of Magnetics
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• v.21 no.2
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• pp.192-196
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• 2016

The Fe-Si-B-Nb-Cu alloys containing Ca and Al were rapidly solidified to thin ribbons by melt-spinning. The ribbons were ball-milled to make powders, and then mixed with 1 wt.% water glass and 1.5 wt.% lubricant. The mixed powders were burn-off, and then compacted to form toroidal-shaped cores, which were heat treated to crystallize the nano-grain structure and to remove residual stress of material. The characteristics of the powder cores were analyzed using a differential scanning calorimetry (DSC) and a B-H meter. The microstructures were observed using transmission electron microscope (TEM). The optimized soft magnetic properties (${\mu}_i$ and $P_{cv}$) of the powder cores were obtained from the Ca and Al containing alloys after annealing at $530^{\circ}C$ for 1 h. The core loss of Fe-Si-B-Nb-Cu-based powder cores was reduced by the addition of Ca element, and the initial permeability increased due to the addition of Al element.

• Journal of the Korean institute of surface engineering
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• v.50 no.5
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• pp.315-321
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• 2017

Antireflective pyramid arrays can be readily obtained via anisotropic etching in alkaline solution (KOH, NaOH), which is widely used in crystalline-Si (c-Si) solar cells. The periodic inverted pyramid arrays show even lower light reflectivity because of their superior light-trapping characteristics. Since this inverted pyramidal structures are mostly achieved using very complex techniques such as photolithograpy and laser processes requiring extra costs, here, we demonstrate the Cu-nanoparticle assisted chemical etching processes to make the inverted pyramidal arrays without the need of photolithography. We have mainly controlled the concentration of $Cu(NO_3)_2$, HF, $H_2O_2$ and temperature as well as time factors that affecting the reaction. Optimal inverted pyramid structure was obtained through reaction parameters control. The reflectance of inverted pyramid arrays showed < 10% over 400 to 1100 nm wavelength range while showing 15~20% in random pyramid arrays.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.4
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• pp.1-7
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• 1999

We developed Fabrication process of embedded passive components in MCM-D substrate. The proposed MCM-D substrate is based on Cu/photosensitive BCB multilayer. The substrate used is Si wafer and Ti/cu metallization is used to form the interconnect layer. Interconnect layers are formed with 1000$\AA$ Ti/3000$\AA$ Cu by sputtering method and 3$\mu\textrm{m}$ Cu by electrical plating method. In order to form the vias in photosensitive BCB layer, the process of BCB and plasma etch using $C_2F_6$ gas were evaluated. The MCM-D substrate is composed of 5 dielectric layers and 4 interconnect layers. Embedded resistors are made with NiCr and implemented on the $2^{nd}$ dielectric layer. The sheet resistance of NiCr is controlled to be about 21 $\Omega$/sq at the thickness of 600$\AA$. The multi-turn sprial inductors are designed in coplanar fashion on the $4^{th}$ interconnect layer with an underpass from the center to outside using the lower $3^{rd}$ interconnect layer. Capacitors are designed and realized between $1^{st}$ interconnect layer and $2^{nd}$ interconnect layer. An important issue in capacitor is the accurate determination of the dielectric thickness. We use the 900$\AA$ thickness of PECVD silicon nitride film as dielectric. Capacitance per unit area is about 88nF/$\textrm {cm}^2$at the thickness of 900$\AA$. The advantage of this integration process is the compatibility with the conventional semiconductor process due to low temperature PECVD silicon nitride process and thermal evaporation NiCr process.

• Korean Journal of Materials Research
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• v.23 no.6
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• pp.304-308
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• 2013

The effect of a sputter deposition sequence of Cu, Zn, and Sn metal layers on the properties of $Cu_2ZnSnS_4$ (CZTS) was systematically studied for solar cell applications. The set of Cu/Sn/Zn/Cu multi metal films was deposited on a Mo/$SiO_2$/Si wafer using dc sputtering. CZTS films were prepared through a sulfurization process of the Cu/Sn/Zn/Cu metal layers at $500^{\circ}C$ in a $H_2S$ gas environment. $H_2S$ (0.1%) gas of 200 standard cubic centimeters per minute was supplied in the cold-wall sulfurization reactor. The metal film prepared by one-cycle deposition of Cu(360 nm)/Sn(400 nm)/Zn(400 nm)/Cu(440 nm) had a relatively rough surface due to a well-developed columnar structure growth. A dense and smooth metal surface was achieved for two- or three-cycle deposition of Cu/Sn/Zn/Cu, in which each metal layer thickness was decreased to 200 nm. Moreover, the three-cycle deposition sample showed the best CZTS kesterite structures after 5 hr sulfurization treatment. The two- and three-cycle Cu/Sn/Zn/Cu samples showed high-efficient photoluminescence (PL) spectra after a 3 hr sulfurization treatment, wheres the one-cycle sample yielded poor PL efficiency. The PL spectra of the three-cycle sample showed a broad peak in the range of 700-1000 nm, peaked at 870 nm (1.425 eV). This result is in good agreement with the reported bandgap energy of CZTS.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.75-78
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• 1996

The deposition condition Gf TiN films as electrode was studied by sheet resistance, TiN depositon Thickness X-ray diffraction. TiN was made by reactively DC magnetron sputtering with varying $N_2$/Ar mixture gas and substrate temperature. After finding The deposition condition of TiN films, The samples with the structure of Cu/Ta$_2$O$_{5}$, TiN/Ta$_2$O$_{5}$Si, Cu/TiN/Ta$_2$O$_{5}$ Si were prepared and were measured I-V, C-V. As a results, it was found that when TiN was deposited in an $N_2$a results, it was found that when TiN was deposited in an $N_2$atmosphere its Sheet resistance is lower n than n V$_2$Ar mixtureixture

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.278-279
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• 2006

The increasing demand for automotive industries to reduce the weight of the vehicles has led to a growing usage of Al alloy powder metallurgy (P/M) parts. In order to control the sintered microstructure and mechanical properties of the aluminium alloy powder metallurgical (P/M) parts, it is essential to establish a fundamental understanding of the microstructural development during the sintering process. This paper presents a detailed study of the effect of temperature and initial starting materials on the evolution of microstructure during the sintering of Al-Cu-Mg-Si blends for PM.

• Journal of Technologic Dentistry
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• v.31 no.4
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• pp.31-36
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• 2009

This study evaluated the grindability of series of Ti-Cu alloys in order to develop a Ti alloy with better grindability than commercially pure titanium(CP Ti). Experimental Ti-Xwt%Cu alloys(X=2, 5, 10) were made in an argon-arc melting furnace. Slabs of experimental alloys were ground using a SiC abrasive wheel on an electric handpiece at circumferential speed(15000, 30000rpm) by applying a force(250, 300gr). Grindability was evaluated by measuring the amount of metal volume removed after grinding for 2 minutes. Data were compared to those for CP Ti and Ti-6wt%Al-4wt%V alloy. From results, It was observed that the grindability of Ti-Cu alloys increased with an increase in the Cu concentration compared to CP Ti, particularly the 10wt%Cu alloy exhibited the highest grindability at all speeds. By alloying with Cu, the Ti exhibited better grindability at high speed. The continuous precipitation of $Ti_2Cu$ among the ${\alpha}$-matrix grains made this material less ductile and facilitated more effective grinding because small segments more readily formed. The Ti-10wt%Cu alloy has a great potential for use as a dental machining alloy.

• Journal of the Korean Vacuum Society
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• v.4 no.S1
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• pp.113-117
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• 1995

MOCVD of Cu films were carried out on gold-TiN(1000$\AA$)/Ti/Si wafers from hexafluoroacetylacetonate-Cu(l) vinyltrimethylsilane, Cu(l)(hafac)(vtms), in a small cold-wall type reactor. Effects of the substrate and bubbler temperatures on the film growth rate were studied, and a film with $\rho$=1.8$\pm$0.1$\mu$$\Omega$.cm could be deposited 150nm/min at Ts=200 and Tb=$30^{\circ}C$, respectively. The initial stage of the film formation was also investigated by in-situ laser reflectivity monitoring combined with SEM observations, based on which variations in the film properties depending on the growth conditions were discussed in terms of the nucleation rate and grain size.

• Journal of Powder Materials
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• v.15 no.2
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• pp.142-147
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• 2008

The hypereutectic Al-20 wt%Si powders including some amount of Cu, Fe, Mg, Mn were prepared by a gas atomization process. In order to get highly densified Al-Si bulk specimens, the as-atomized and sieved powders were extruded at $500^{\circ}C$, Microstructure and tensile properties of the extruded Al-Si alloys were investigated in this study. Relative density of the extruded samples was over 98%. Ultimate tensile strength (UTS) in stress-strain curves of the extruded powders increased after T6 heat treatments. Elongation of the samples was also increased from 1.4% to 3.2%. The fracture surfaces of the tested pieces showed a fine microstructure and the average grain size was about $1{\mu}m$.