• Korean Journal of Materials Research
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• v.19 no.12
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• pp.637-643
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• 2009

In this study, we analyzed the effect of silicon oxynitride matrix on the optical properties of Au nanoparticles dispersed on composite film and explored the effectiveness of the silicon in fine tuning the refractive index of the composite film for applications in optical waveguide devices. The atomic fraction of nitrogen in $SiO_xN_y$ films was controlled by varying the relative flow ratio of nitrogen gas in reactive sputtering and was evaluated optically using an effective medium theory with Bruggeman geometry consisting of a random mixture between $SiO_2$ and $Si_3N_4$. The Au nanoparticles were embedded in the $SiO_xN_y$ matrix by employing the alternating deposition technique and clearly showed an absorption peak due to the excitation of surface plasmon. With increasing nitrogen atomic fraction in the matrix, the surface plasmon resonance wavelength shifted to a longer wavelength (a red-shift) with an enhanced resonance absorption. These characteristics were interpreted using the Maxwell-Garnett effective medium theory. The formation of a guided mode in a slab waveguide consisting of 3 $\mu$m thick Au:$SiO_xN_y$ nanocomposite film was confirmed at the telecommunication wavelength of 1550 nm by prism coupler method and compared with the case of using $SiO_2$ matrix. The use of $SiO_xN_y$ matrix provides an effective way of controlling the mode confinement while maintaining or even enhancing the surface plasmon resonance properties.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.204-210
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• 2008

$1.5\;{\mu}m$-thick copper films deposited on silicon wafers were successfully bonded at $415^{\circ}C$/25 kN for 40 minutes in a thermo-compression bonding method that did not involve a pre-cleaning or pre-annealing process. The original copper bonding interface disappeared and showed a homogeneous microstructure with few voids at the original bonding interface. Quantitative interfacial adhesion energies were greater than $10.4\;J/m^2$ as measured via a four-point bending test. Post-bonding annealing at a temperature that was less than $300^{\circ}C$ had only a slight effect on the bonding energy, whereas an oxygen environment significantly deteriorated the bonding energy over $400^{\circ}C$. This was most likely due to the fast growth of brittle interfacial oxides. Therefore, the annealing environment and temperature conditions greatly affect the interfacial bonding energy and reliability in Cu-Cu bonded wafer stacks.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.93-99
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• 2011

We investigated how the surface roughness of electrode affects the charge injection at the pentacene/Au interface. After depositing Au film on the Si substrate by sputtering, we annealed the sample to control the Au surface roughness. Pentacene and Au top electrode were subsequently deposited to complete the sample. The nucleation density of pentacene was slightly higher on the rougher Au electrode, but surface morphologies of thick pentacene films were similar on both the as-prepared and the roughened Au electrodes. The current-voltage curves obtained from the Au/pentacene/Au structure measured as a function of temperature indicated that the interface barrier was higher for the rougher Au bottom-electrode. We propose that the higher barrier was caused by the lower work function of rougher electrode surface and the higher trap density at the interface.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.5
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• pp.696-702
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• 2002

The BST $({Bal-xSrxTiO_3})$ (50/50) thin film has been grown by RF magnetron reactive sputtering and its characteristics such as crystallization, surface roughness, and electrical properties have been investigated with varying the film thickness. The crystallization and surface roughness of BST thin film are investigated by using XRD and AFM, respectively. The BST thin film annealed at $800^{\circ}C$ for 2 min has pure perovskite structure and good surface roughness of 16.1$\AA$. As the film thickness increases from 80 nm to 240 nm, the dielectric constant at 10 KHz increases from 199 to 265 and the leakage current density at 250 ㎸/cm decreases from $0.779 {\mu}A/{cm^2} to 0.184 {\mu}A/{cm^2}$. In the case of 240 nm-thick BST thin film, the charge storage density and leakage current density at 5V are 50.5 fC/${{\mu}m^2} and 0.182 {\mu}A/{cm^2}$, respectively. The values indicate that the BST thin film is a very useful dielectric material for the DRAM capacitor.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1988-1989
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• 2007

Polyethylene is widely used as the insulator for power cable. To investigate the conduction mechanism for power cable insulation under ac high field, it is very important to acquire the dissipation current under actual running field. Recently, we have developed the unique system, which make possible to observe the nonlinear dissipation current waveform. In this system, to observe the nonlinear properties with high accuracy, capacitive current component is canceled by using inverse capacitive current signal instead of using the bridge circuit for canceling it. We have already reported that the dissipation currents of $40\;{\mu}m$ thick LDPE film at 10 kV/mm and over 140 Hz, it starts to show nonlinearity and odd number's harmonics were getting large. To investigate the conduction mechanis ms in this region, especially space charge effect, various kinds of estimation, such as time variations of instantaneous resistivity for one cycle, FFT spectra of dissipation current waveforms and so on, has been examined. As the results of these estimations, it was found that the dissipation current will depend on not only the instantaneous value of electric field but also the time differential of applied electric field due to taking a balance between applied field and internal field. Furthermore, two large peaks of dissipation current for each half cycle were observed under certain condition. In this paper, to clarify the reason why it shows two peaks for each half cycle, the film thickness dependences of dissipation current waveforms were observed by using the three different thickness LDPE films.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.118-118
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• 2010

현재 반도체 제조 공정 중 많은 비중을 차지하는 식각 및 증착 공정에는 대부분 플라즈마를 사용하고 있으며, 이러한 반도체 장비내의 공정 부분품들은 수율과 생산성을 향상시키기 위하여 내플라즈마 특성이 우수한 세라믹 또는 세라믹 코팅막으로 구성되어 있다. 더욱이 최근에는 미세공정을 위해 고밀도 플라즈마 공정이 요구되면서, 노출된 세라믹 층이 침식되어 파티클이 떨어져 나오거나 모재와 세라믹 막 사이의 박리현상과 같은 심각한 문제들이 발생되고 있다. 따라서 보다 우수한 내플라즈마 특성을 갖는 세라믹 코팅 기술 개발이 시급한 실정이다. 현재 내플라즈마성 세라믹 코팅막 제조를 위한 코팅기술로서는 주로 용사법이 이용되고 있으나 기공률이 높고 치밀하지 못한 등의 문제점으로 인하여 사용수명이 짧다는 한계에 봉착하였다. 이에 본 연구에서는 상온에서 치밀하고 고속으로 세라믹 후막 형성이 가능한 Aerosol Deposition (AD)법과 AD법의 단점인 edge, corner, hole에서 코팅이 잘 안 되는 점을 보완할 수 있는 Arc Plasma Anodizing (APA)법을 조합하여, 상용화된 Al 모재위에 APA법을 사용하여 $Al_2O_3$ 후막 중간층을 형성한 뒤 그 위에 AD법으로 치밀한 $Al_2O_3$ 후막 성막함으로써 내 플라즈마 향상을 위한 새로운 개념의 제조기술개발을 시도하였다. 이를 위해 우선 Al 모재 위에 APA를 사용하여 중간층인 $Al_2O_3$막을 제조하였으며, 중간층의 두께에 따른 특성을 확인한 결과, $Al_2O_3$중간층의 두께가 두꺼워질수록 표면조도가 증가함을 확인 할 수 있었다. AD법으로 $Al_2O_3$중간층 위에 치밀한 $Al_2O_3$막을 제조하는데 있어 중요인자를 확인하기 위해, AD법으로 중간층 위에 $Al_2O_3$막을 제조한 후 성막특성을 관찰하였다. 그 결과, 중간층의 표면조도가 $0.8-1\;{\mu}m$인 경우에는 수 ${\mu}m$의 두께로 성막 되었으나, 표면조도가 $1\;{\mu}m$ 이상인 $Al_2O_3$중간층 위에서는 성막 되지 않았다. 이를 통해 AD법으로 치밀하고 두꺼운 $Al_2O_3$ 후막을 $Al_2O_3$중간층 위에 성막하기 위해서는 표면조도가 중요인자임을 확인하였다.

• Korean Journal of Materials Research
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• v.16 no.10
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• pp.606-613
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• 2006

This study was purposed to evaluate the influence of anodically oxidized film on titanium (Ti) onto MG-63 osteoblast-like cell attachment and activity. Only scratch lines created by polishing were seen in ASR and ANO-1 groups. About $1.5{\mu}m$-thick homogeneous oxide film which has pores of about $0.5{\mu}m$ diameter were formed in ANO-12. The crystalline structure of the oxide films formed by anodization in phosphoric acid electrolyte was $TiP_2O_7$. The total protein amounts of ANO-1 and ANO-12 groups showed higher values of maximum protein amount than that of AS-R group. At 3 days of incubation, total protein amount showed higher value in ANO-2 when comparing to that of AS-R (p<0.05). Based on the results of ALPase activity test, the degree of MG-63 cell differentiation for initial mineralization matrix formation was similar. For all the test groups after 1 day of incubation, MG-63 cells grew healthily in mono-layer with dendritic extensions. After incubation for 3 days, the specimen surfaces were covered more densely by cells, and numerous micro filaments were extruding to the extracellular matrix.

• Korean Journal of Materials Research
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• v.22 no.7
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• pp.358-361
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• 2012

Co and Ni as catalysts in $SnO_2$ sensors to improve the sensitivity for $CH_4$ gas and $CH_3CH_2CH_3$ gas were coated by a solution reduction method. $SnO_2$ thick films were prepared by a screen-printing method onto $Al_2O_3$ substrates with an electrode. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a chamber. The structural properties of $SnO_2$ with a rutile structure investigated by XRD showed a (110) dominant $SnO_2$ peak. The particle size of the $SnO_2$:Ni powders with Ni at 6 wt% was about 0.1 ${\mu}m$. The $SnO_2$ particles were found to contain many pores according to a SEM analysis. The sensitivity of $SnO_2$-based sensors was measured for 5 ppm of $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air to that in the target gases. The results showed that the best sensitivity of $SnO_2$:Ni and $SnO_2$:Co sensors for $CH_4$ gas and $CH_3CH_2CH_3$ gas at room temperature was observed in $SnO_2$:Ni sensors coated with 6 wt% Ni. The $SnO_2$:Ni gas sensors showed good selectivity to $CH_4$ gas. The response time and recovery time of the $SnO_2$:Ni gas sensors for the $CH_4$ and $CH_3CH_2CH_3$ gases were 20 seconds and 9 seconds, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.615-620
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• 2008

We fabriacted thermal evaporated $10nm-Ni_{1-x}Co_x$(x=0.2, 0.6, and 0.7) films on 70 nm-thick polysilicon substrate with $0.5{\mu}m$ line width. NiCo composite silicide layers were formed by rapid thermal annealing (RTA) at the temperatures of $700^{\circ}C$ and $1000^{\circ}C$. Then, we checked the microstructure evaluation of silicide patterns. A FIB (focused ion beam) was used to micro-mill the interconnect patterns with low energy condition (30kV-10pA-2 sec). We investigated the possibility of selective removal of silicide layers. It was possible to remove low resistance silicide layer selectively with the given FIB condition for our proposed NiCo composite silicides. However, the silicides formed from $Ni_{40}Co_{60}$ and $Ni_{30}Co_{70}$ composition showed void defects in interconnect patterns. Those void defects hinder the selective milling for the NiCo composite silicides.

• Journal of the Korean institute of surface engineering
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• v.47 no.5
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• pp.263-268
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• 2014

Nanocrystalline diamond(NCD) coated SiC balls were applied in a ball-on-disk tribometer. After seeding in an ultrasonic bath containing nanometer diamond powders, $2.2{\mu}m$ thick NCD films were deposited on sintered 3 mm diameter SiC balls at $600^{\circ}C$ in a 2.45 GHz microwave plasma CVD system. Bare $ZrO_2$ and SiC balls were prepared for comparison as test balls. Tribology tests were performed in air with pairs of three different balls and mirror polished steel(SKH51) disk. The wear tracks on balls and disks were examined by optical microscope and alpha step profiler. Under the load of 3 N, the friction coefficients of steel against $ZrO_2$, SiC and NCD-coated balls were between 0.4 and 0.8. After a few thousands sliding laps, the friction coefficient of NCD-coated balls dropped from 0.45 to below 0.1 and maintained thereafter. Under a higher load of 10 N or 20 N with a long sliding distance of 2 km, $ZrO_2$ and SiC balls exhibited the similar friction coefficients as above. The friction coefficient of NCD-coated balls was less than 0.1 from the beginning and increased to above 0.1 steadily or with some fluctuations as sliding distance increased. NCD coating layers were found worn out after long duration and/or high load sliding test, which resulted in the friction coefficient higher than 0.1.