• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.967-972
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• 2004

The role of transfer films formed during sliding of polymer composites against steel counterfaces was studied in terms of the tribological behaviors of composites. Four kinds of composites were included in this study: (1) unfilled PPS, (2) PPS+2%CuO, (3) PPS+2%CuO+5% carbon fiber (CF), and (4) PPS+2%CuO+15%Kevlar. The filler material CuO was in nanoscale particulate form and the reinforcing material was in the form of short fibers. The composites were prepared by compression molding at $310^{\circ}C$ and sliding tests were run in the pin-on-disk sliding configuration. The counterface was made of tool steel hardened to 55-60 HRC and finished to a surface roughness of 0.09-0.10 ${\mu}m$ Ra. Wear tests were run for 6 hrs at the sliding speed of 1 m/s and contact pressure of 0.65 MPa. Transfer films formed on the counterfaces during sliding were investigated using AFM and SEM. The results showed that as the transfer film became smooth and uniform, wear rate decreased. PPS+2%CuO+15%Kevlar composite showed the lowest steady state wear rate in this study and its transfer film showed the smoothest and the most uniform characteristics. The examination of worn surfaces of PPS+2%CuO composite using X-ray area scanning (dot mapping) showed back-transfer of steel counterface material to the polymer pin surface. This behavior is believed to strengthen the polymer pin surface during sliding thereby contributing to the decrease in wear rate.

• 한국생산제조학회지
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• 제24권5호
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• pp.475-480
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• 2015

Ultrasonic atomic force microscopy (Ultrasonic-AFM) has been used to investigate the elastic property of the ultra-thin coating layer in a thin-film system. The modified Hertzian theory was applied to predict the contact resonance frequency through accurate theoretical analysis of the dynamic characteristics of the cantilever. We coat 200 nm thick Aluminum and Titanium thin films on the substrate using the DC Magnetron sputtering method. The amplitude and phase of the contact resonance frequency of a vibrating cantilever varies in response to the local stiffness constant. Ultrasonic-AFM images were obtained using the variations in the elastic property of the materials. The morphology of the surface was clearly observed in the Ultrasonic-AFM images, but was barely visible in the topography. This research demonstrates that Ultrasonic-AFM is a promising technique for visualizing the distribution of local stiffness in the nano-scale thin coatings.

• KSTLE International Journal
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• 제9권1_2호
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• pp.22-25
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• 2008

This paper investigated the wetting and adhesion property of undulated DLC film with surface morphology controlled for a reduced real area of contact. The undulated DLC Films were prepared by 13.56 MHZ radio frequency plasma enhanced chemical vapor deposition (r.f. PECVD) by using nanoscale Cu dots surface on a Si (100) substrate. FE-SEM, AFM analysis showed that the after repeated deposition and plasma induced damage with Ar ions, the surface was nanoscale undulated. This phenomenon changed the surface morphology of DLC surface. Raman spectra of film with changed morphology revealed that the plasma induced damage with Ar ions significantly suppressed the graphitization of DLC structure. Also, it was observed that while the untreated flat DLC surfaces had wetting angle starting ranged from $72^{\circ}$ and adhesion force of 333ni. Had wetting angle the undulated DLC surfaces, which resemble the surface morphology of a cylindrical shape, increased up to $104^{\circ}$ and adhesion force decreased down to 11 nN. The measurements agree with Hertz and JKR models. The surface undulation was affected mainly by several factors: the surface morphology affinity to cylindrical shape, reduction of the real area of contact and air pockets trapped in cylindrical asperities of the surface.

• 비파괴검사학회지
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• 제36권4호
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• pp.266-272
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• 2016

본 논문에서는 나노스케일 금속박막 내에서 체적종파가 전파하는 특성을 연구하였다. 실리콘(100) 기판 위에 150 nm 두께의 크로뮴 혹은 알루미늄 박막을 적층하여 시편을 제작하였으며, 펨토초 레이저 시스템으로 구성된 시간영역 열반사율 기법(time-domain theromoreflectance technique)을 이용하여 박막 표면으로부터 여기된 탄성파가 박막과 기판의 계면에서 반향될 때 발생하는 신호를 검출하였다. 체적종파의 거동을 모사하는 열탄성 방정식을 수치해석적으로 풀어 측정값과 곡선맞춤함으로써 박막의 체적종파 속도와 탄성계수를 평가할 수 있었으며, 결과를 문헌값과 비교하여 그 타당성을 검증하였다. 본 연구로부터 확립된 레이저 계측법은 나노재료의 특성평가에 적합함을 보여주며, 이는 기존의 접촉식 파괴식 검사법의 한계를 뛰어넘을 대안을 제시한다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
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• pp.21-21
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• 2003

Microstructure and magnetic transport phenomina in rf sputtered AlN/Co type ten-layered discontinuous films of nanoscaled [AlN (3 nm)/Co (t nm)]...$\sub$10/ with t$\sub$Co/=1.0∼2.0 nm have been investigated. The microstructure and tunneling magnetic resistance of the samples are strongly dependent on the thickness of Co layer. Negative tunneling magneto-resistance due to the spin-dependent transport has been observed along the current-in-plane configuration in the samples having the Co layers below 1.6 nm thick. When the thickness of Co layer was less than 1,2 nm, randomly oriented granular Co particles were completely isolated and embedded in amorphous AlN matrix, and the films showed the superparamagnetic behavior with a high MR value of Δ$\rho$/$\rho$$\sub$0/=1.8 %. As t$\sub$Co/ increases, a transition from the regime of co-existence of superparamagnetic and ferromagnetic behaviors to ferromagnetic behavior was observed. Tunneling barrier called "decay length for tunneling" for the films having the thickness of Co layer from 1.4 to 1.6 nm was measured to be ranged from 0.004 to 0.021 ${\AA}$$\^$-1/.

• Journal of Magnetics
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• 제8권2호
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• pp.98-102
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• 2003

Microstructure and magnetic transport phenomina in rf sputtered AIN/CO type ten- layered discontinuous films of nanoscaled [AIN(3 nm)/Co(t nm)]…$_10$ with t$_Co$=1.0∼2.0 nm have been investigated. The microstructure and tunneling magnetic resistance of the samples are strongly dependent on the thickness of Co layer, Negative tunneling magneto-resistance due to the spin-dependent transport has been observed along the current-in-plane configuration in the samples having the Co layers below 1.6 nm thick. When the thickness of Co layer was less than 1.2 nm, randomly oriented granular Co particles were completely isolated and embedded in amorphous AIN matrix, and the films showed the superparamagnetic behavior with a high MR value of ${\Delta}p/p_0$=1.8%. As t$_Co$ increases, a transition from the regime of co-existence of superparamagnetic and ferromagnetic behaviors to ferromagnetic behavior was observed. funneling barrier called “decay length far tunneling” fur the films haying the thickness of Co layer from 1.4 to 1.6 nm was measured to be ranged from 0.004 to 0.021 ${\AA}$$^{-1}$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.323-323
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• 2012

We present ferroelectricity of Bi-doped ZnO film probed by piezoresponse force microscopy (PFM), which is one of the Scanning Probe Microscopy techniques. Perovskite ferroelectrics are limited to integration of devices into semiconductor microcircuitry due to hard adjusting their lattice structure to the semiconductor materials. Transition metal doped ZnO film is one of the candidate materials for replacing the perovskite ferroelectrics. In this study, ferroelectric characteristics of the Bi-doped ZnO grown by pulsed laser deposition were probed by PFM. The polarization switching and patterning of the ZnO films were performed by applying DC bias voltage between the AFM tips and the films with varying voltages and polarity. The PFM contrast before and after patterning showed clearly polarization switching for a specific concentration of Bi atoms. In addition, the patterned regions with nanoscale show clearly the local piezoresponse hysteresis loop. The spontaneous polarization of the ZnO film is estimated from the local piezoresponse based on the comparison with LiNbO3 single crystals.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
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• pp.251-265
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• 2000

S $m_{2}$F $e_{17}$ $N_{x}$ film magnets using a S $m_{2}$F $e_{17}$ target were prepared at $N_{2}$ gas atmosphere using a Nd-YAG laser ablation technique. The effect of nitrogen pressure, deposition temperature, pulsation time and film thickness on the structure and magnetic properties of S $m_{2}$F $e_{17}$ $N_{x}$ film were studied. Increasing the nitrogen pressure up to 5 atm. was confirmed to lead the formation of complete S $m_{2}$F $e_{17}$ $N_{x}$ compound. Optimized magnetic properties with the nitrogenation temperature ranging over 500-53$0^{\circ}C$ could be obtained by extending the nitrogenation time up to 4 hours. Relatively low coercivities of 400~600 Oe were exhibited from the S $m_{2}$F $e_{17}$ $N_{x}$ films having the thickness of 50~100 nm while 4$\pi$ $M_{s}$ of 10~12 kG could be achieved. In-plane anisotropic characteristic, which was the basic goal in this study, was achieved by controlling the nitrogenation parameters.ameters.ers.ameters.

• 한국표면공학회지
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• 제48권2호
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• pp.38-42
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• 2015

Atomic layer deposition (ALD) is essential for the fabrication of nanoscale electronic devices because it has excellent conformality, atomic scale thickness control, and large area uniformity. Metal thin films are one of the important material components for electronic devices as a conductor. As the size of electronic devices shrinks, the thickness of metal thin films is decreased down to few nanometers, and the metal films become non-continuous due to inherent island growth of metal below a critical thickness. So, fabrication of continuous metal thin films by ALD is fundamentally and practically important. Since ALD films are grown through self-saturated reactions between precursors on surface, initial growth characteristics significantly depend on the surface properties and the selection of precursors. In this work, we investigated ALD Pt on $TiO_2$ substrate by using trimethyl-methyl-cyclopentadienyl-Platinum ($MeCpPtMe_3$) precursor and $O_3$ reactant. By using $O_3$ instead of $O_2$, initial nucleation rate of ALD Pt was increased on $TiO_2$ surface, resulting in formation of continuous thin Pt films. Morphologies of ALD Pt on $TiO_2$ were characterized by using Scanning Electron Microscope (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). Crystallinity of ALD Pt on $TiO_2$ correlated with its growth characteristics was analyzed by X-Ray Diffraction (XRD).

• 한국자기학회지
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• 제3권1호
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• pp.23-28
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• 1993

복합타게트 방식의 고주파 2극 마그네트론 스퍼터링 장치를 이용하여 Fe-Hf-C계 극미세 결정 연자성 박막을 제조하여 박막조성, 열처리 조건 및 기판과 그 하지층이 자기적 성질에 미치는 영향을 조사하였다. Fe-Hf-C계 초미세 결정 연자성 박막은 Hf 8-10at.%, C 14-18at.%의 조성범위에 서 비정질과 결정질의 경계에 가까운 조성일수록 연자성이 향상되었으며 포화자속밀도 16 kG, 1 MHz 에서의 실효투자율 4000 이상의 연자성을 나타내고 $600^{\circ}C$ 까지도 투자율 3000정도의 열적안정 성을 나타내었다. 기판 및 하지층에 따른 연자성 특성은 미세구조의 변화 보다는 기판/자성막 및 하지층/자성막간의 상호확산에 의해 주로 영향을 받는 것으로 나타났다.