• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.447-452
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• 2014

This paper presents the effects of pulse plasma parameters such as duty cycle and pulse frequency on the properties of TiAlN coatings deposited by asymmetric bipolar pulsed DC magnetron sputtering systems. The results show that, with decreasing duty cycle and increasing pulse frequency, the coating morphology changes from a columnar structure to a dense structure with finer grains. Pulsed sputtered TiAlN coatings showed higher hardness, higher residual stress, and smaller grain sizes than did DC prepared TiAlN coatings. Moreover, residual stress and nanoindentation hardness of pulsed sputtered TiAlN coatings increased with increasing pulse frequency. Meanwhile, the surface roughness decreased continuously with increasing pulsed DC frequency up to 50 kHz.

• Journal of the Korean institute of surface engineering
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• v.28 no.2
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• pp.67-76
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• 1995

The microstructure of 95wt.%Pb/5wt.%Sn and 63wt.%Sn/37wt.%Pb solders for flip chip bonding process has been characterized. Solders were deposited by thermal evaporation and reflowed in the conventional furnace or by rapid thermal annealing(RTA) process. As-deposited films show columnar structure. The microstructure of furnace cooled 63Sn/37Pb solder shows typical lamellar form, but that of RTA treated solder has the structure showing an uniform dispersion of Pb-rich phase in Sn matrix. The grain size of 95Pb/5Sn solder reflowed in the furnace is about $5\mu\textrm{m}$, but the grain size of RTA treated solder is too small to be observed. The microstructure in 63Sn/37Pb solder bump shows the segregation of Pb phase in the Sn rich matrix regardless of reflowing method. The 63Sn/37Pb solder bump formed by RTA process shows more uniform microstructure. These result are related to the heat dissipation in the solder bump.

• Journal of the Korean institute of surface engineering
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• v.33 no.2
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• pp.115-125
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• 2000

TiN films were deposited onto Stellite 6B alloy (Co base) by the reactive magnetron sputter ion plating. As the bias increases, TiN film changes from columnar structure to dense structure with great hardness and smooth surface due to densification and resputtering by ion bombardment. The content of oxygen and carbon impurities in the TiN film decreases greatly when the substrate bias is applied. The preferred orientation of the TiN films changes from (200) to (111) with decreasing $N_2$/Ar ratio, and from (200) to (111) and then (220) with increasing the substrate bias. The change of the preferred orientation is discussed in terms of surface energy and strain energy which are related to the impurity contents and the ion bombardment damage. The hardness of the TiN film increases with increasing compressive stress generated in the film by virtue of ion bombardment. It becomes as high as up to 3500kgf/mm$^2$ when an appropriate substrate bias is applied.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.52 no.1
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• pp.14-19
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• 2003

The effect of the Pt electrode and the $Pt-IrO_2$ hybrid electrode on the performance of ferroelectric device was investigated. The modified Pt thin films with non-columnar structure significantly reduced the oxidation of TiN diffusion barrier layer, which rendered it possible to incorporate the simple stacked structure of Pt/TiN/poly-Si plug. When a $Pt-IrO_2$ hybrid electrode is applied, PZT thin film properties are influenced by the thickness and the partial coverage of the electrode layers. The optimized $Pt-IrO_2$ hybrid electrode significantly enhanced the fatigue properties of the PZT thin film with minimal leakage current.

• Journal of Korea Foundry Society
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• v.15 no.4
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• pp.408-415
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• 1995

Polycrystalline Al-Cu ribbons were produced by planar flow casting(PFC). Solidification behavior and microstructual changes of the ribbons have been investigated as a function of ribbon thickness and processing parameters. The solidification front velocity, V varies within the ribbon, decreasing with increasing the distance, S from the wheel-contact surface, as $V=17.6S^{-1}$. In Al-4.5wt%Cu alloy, rapid decrease in solidification velocity toward the free surface causes a change in solidification morphology from planar to cellular, and finally, to dendritic. The length and inclination of columnar grains solidified with planar front were related to the wheel velocity. The transition from particulate degenerate eutectic structure to regular lamellar eutectic structure was observed to be caused by a difference of the relative growth velocites of ${\alpha}-Al$ and ${\theta}$ during solidification in the Al-Cu eutectic alloy.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.248-248
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• 2006

The notable feature of the Cu(II) coordination polymer investigated here is its ability to self-assemble into a double-stranded helical structure with regular grooves along the helical axis, through the combination of metal-chloride dimeric interactions and repulsive interactions, as an organizing force. It is also remarkable that the double-stranded helices self-organize into a 2-D columnar structure in both the bulk state and aqueous solution. These results represent a unique example that weak metal-ligand bridging interactions can provide a useful strategy to construct stable double-stranded helical nanotubes.

• Journal of the Korean Ceramic Society
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• v.50 no.3
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• pp.212-217
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• 2013

Ultra hard TiN coatings were fabricated by DC and ICP (inductively coupled plasma) magnetron sputtering techniques. The effects of ICP power, ranging from 0 to 300 W, on the coating microstructure, crystallographic, and mechanical properties were systematically investigated with FE-SEM, AFM, HR-XRD and nanoindentation. The results show that ICP power has a significant influence on the coating microstructure and mechanical properties of TiN coatings. With an increasing ICP power, the film microstructure evolves from an apparent columnar structure to a highly dense one. Grain sizes of TiN coatings decreased from 12.6 nm to 8.7 nm with an increase of the ICP power. A maximum nanohardness of 67.6 GPa was obtained for the coatings deposited at an ICP power of 300 W. The crystal structure and preferred orientation in the TiN coatings also varied with the ICP power, exerting an effective influence on film nanohardness.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.322.2-322.2
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• 2014

Lighting emitting diodes of n-ZnO/MQW/p-GaN structure are fabricated and investigated. To realize this LED structure, n-ZnO/MQW/p-GaN are grown by MOCVD. At several bias voltages, blue-green light is emitted from the ZnO mesa edge. However, the emission is restricted near the mesa edge. It is seen that the hole current does not spread well. It is because conductivity of p-GaN is extremely small. The break down voltage of the device is small compared to conventional InGaN/GaN LEDs. It is seen that ZnO columnar grain boundaries act as leakage current paths and non-radiative recombination center.

• Journal of the Korean Society for Heat Treatment
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• v.5 no.2
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• pp.95-102
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• 1992

In this study, we tried to describe the quantitative model of TiN film structure which was deposited by PECVD process. The macro-grain growth behavior was studied at the various deposition pressures and times. As a result, It was confirmed that TiN films had the typical Zone 1 structure, and macro-columnar grains were, without reference to the deposition pressure, grown ballistic type by the growth-death competition following the equation, $Y=aX^2$, approximately obtained by regression analysis. Also, the thickness and the crystallization of TiN thin films were increased, the chlorine contents were decreased according to the decreasing of deposition pressure.

• Journal of the Korean institute of surface engineering
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• v.18 no.2
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• pp.53-60
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• 1985

The microstructure of zine electrodeposits was investigated by using zinc sulfate solution in still bath. The cathode current efficiency decreased with increasing current density, and decreasing temperature. The preferred orientation of the zinc electrodeposits changed from (10.3) texture to(10.${\ell}$)-(00.1)(${\ell}$=1, 2, 3) texture through (10.2)-(10.3) preferred orientation with increasing cathode over potential. The surface morphology of zinc electrodeposits changed from the dendritic growth with granular crystallites to the blocks of hexagonal crystallites packed together with increasing current density. The microstructure of cross section of the above deposits are the rough granular structure and columnar structure respectively.