• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1715-1717
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• 2004

We attempt to investigate morphology of self-assembled dipyridinium dithioacetate on Au(111) substrate by Scanning Tunneling Microscopy(STM). Also, we measured electrical properties using Scanning Tunneling Spectroscopy(STS). Sample that use this experiment acquires thiol function beside quantity by dipyridinium dithioacetate, is structure that can be self-assembled easily to Au(111) substrate. The same self-assembly procedure was used for two different concentrations, 0.5mmol/ml and 1mmol/ml. Dilute density of sample by 0.5mmol/ml, 1mmol/ml and observed dipyridinium dithioacetate's image by STM after self-assembled on Au(111) substrate. The structure of Tip/SAMs/Au(111) has been used measurement for electrical properties(i-v) using STM. The current-voltage measurement result, observed negative differential resistance(NDR) properties.

• Journal of Surface Science and Engineering
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• v.45 no.2
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• pp.81-88
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• 2012

Probe tip, which should have not only superior electrical characteristics but also good abrasion resistance for numerous contacts with semiconductor pads to confirm their availability, is essential for MEMS probe card. To obtain good durability of probe tip, it needs thick and crack-free rhodium layer on the tip. However, when the rhodium thickness deposited by electroplating increased, unwanted cracks by high internal stress led to serious problem of MEMS probe tip. This article reported the method of thick Rh deposition with Au buffer layer on the probe tip to overcome the problem of high internal stress and studied mechanical and electrical properties of that. MEMS probe tip with double-Rh layer had good contact resistance and durability during long term touch downs.

• Tribology and Lubricants
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• v.24 no.2
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• pp.63-71
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• 2008

Friction and adhesion tests were conducted to investigate tribological characteristics of materials for MEMS/NEMS using atomic force microscope (AFM). AFM Si tips were chemically modified with a self-assembled monolayer (SAM) derived from trichlorosilane like octadecyltrichlorosilane (OTS) and (1H, 1H, 2H, 2H-perfluorooctyl) trichlorosilane (FOTS), and various materials, such as Si, Al, Au, Cu, Ti and PMMA films, were prepared for the tests. SAMs were coated on Si wafer by dipping method prior to AFM tip to determine a proper dipping time. The proper dipping time was determined from the measurements of contact angle, surface energy and thickness of the SAMs. AFM tips were then coated with SAMs by using the same coating condition. Friction and adhesion forces between the AFM Si tip modified with SAM and MEMS/NEMS materials were measured. These forces were compared to those when AFM tip was uncoated. According to the results, after coating OTS and FOTS, the friction and adhesion forces on all materials used in the tests decreased; however, the effect of SAM on the reduction of friction and adhesion forces could be changed according to counterpart materials. OTS was the most effective to reduce the friction and adhesion forces when counterpart material was Cu film. In case of FOTS, friction and adhesion forces decreased the most effectively on Au films.

• Journal of Sensor Science and Technology
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• v.15 no.4
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• pp.237-244
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• 2006

Atomic force microscope (AFM) has become a common tool for the structural and physical studies of biological macromolecules, mainly because it provides the ability to perform experiments with samples in a buffer solution. In this study, structure of proteins and nucleic acids has been studied in their physiological environment that allows native intermolecular complexes to be formed. Cr and Au were deposited on p-Si (100) substrate by thermal evaporation method in sequence with the thickness of $200{\AA}$ and $500{\AA}$, respectively, since Au is adequate for immobilizing biomolecules by forming a self-assembled monolayer (SAM) with semiconductor-based biosensors. The SAM, streptavidin and biotin interacted each other with their specific binding energy and their adsorption was analyzed using the Bio-AFM both in a solution and under air environment. A silicon nitride tip was used as a contact tip of Bio-AFM measurement in a solution and an antimony doped silicon tip as a tapping tip under air environment. Actual morphology could also be obtained by 3-dimensional AFM images. The length and agglomerate size of biomolecules was measured in stages. Furthermore, $R_{a}$ (average of surface roughness) and $R_{ms}$ (mean square of surface roughness) and surface density for the adsorbed surface were also calculated from the AFM image.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.162-162
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• 2003

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.150-150
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• 2012

본 연구는 1차원 나노 구조의 합성과 기초적 분석에 관한 연구로써 특히 무기 산화물 나노재료를 그 대상으로 하였다. 내용으로는 첫째, 1차원 코어 나노와이어의 합성을 하였고 Thermal evaporation, substrate의 가열, 그리고 MOCVD 를 사용한 결과들을 나열한다. 둘째, 코어-쉘 나노와이어를 제작하기 위하여 특히 쉘층의 제작방법을 연구하였는데 PECVD, ALD, 그리고 sputtering에 의한 결과들을 나열하고 간단히 설명한다. Thermal evaporation에 의한 1차원 나노와이어 합성의 경우는 MgO의 예를 들었는데 MgO 나노와이어는 Au가 증착된 기판을 열처리하여 Au dot를 형성하고 이의 morphology를 조절하여 최적의 나노와이어 합성조건을 선정하였다. 이로써 기판 morphology가 나노선의 성장및 형상에 영향을 준다는 사실을 알게 되었다. 이 사실은 In2O3기판을 사용하고 이의 표면거칠기를 열처리로 조절하므로써 역시 나노와이어의 성장을 촉진하는 방법을 찾아내었다. 또한 thermal evaporation공법은 source분말의 선택에 따라 다양한 소재를 제작가능하다는 결과를 제시하였다. 예를 들면 SiOx 층이 precoating된 chamber내에서 MgO 나노선을 합성하는 것과 동일한 조건으로 실험을 진행하면 Mg2SiO4 나노와이어가 형성된 것을 확인하였다. 또한 Sn과 MgB2 분말을 함께 적용할 경우 Sn tip을 가진 MgO 나노와이어를 얻을 수 있었다. 이는 Sn이 동시에 촉매의 역할을 하였기 때문일 것으로 추정된다. 한편 Sn과 Bi 혼합분말을 적용한 경우 Bi2Sn2O7 신소재 tip을 포함한 SnO2 나노와이어를 얻을 수 있었다. 이 경우 Bi원자가 적절한 촉매의 역할을 수행한 것으로 사료된다. Substrate의 가열공법에서는 Si wafer상에 각종 금속 즉 Au, Ag, Cu, Co, Mo, W, Pt, Pd등 초박막을 DC sputter 로 형성한후 annealing하는 기술을 사용하였다. 특기할 만한 것은 Co를 사용한 경우 나노와이어의 spring구조를 얻을 수 있었다는 점이다. MOCVD에 의하여는 Ga2O3및 Bi2O3 나노와이어를 비교적 저온에서 합성하였고 In2O3의 경우는 독특한 나노구조를 형성하였고 이의 결정학적 특성에 대하여 조사하였다.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.1
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• pp.35-39
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• 2011

Shearing characteristics of Sn-3.0wt%Ag-0.5wt%Cu ball for standardization of high speed shear test were investigated. The solder ball of 450 ${\mu}m$ in diameter was reflowed at $245^{\circ}C$ on FR4 PCB (Printed Circuit Board) to prepare a sample for the high-speed shear test. The metal pads on the PCB were OSP (Organic Solderability Preservative, Cu pad) and ENIG (Electroless Nickel/Immersion Gold, i.e CulNi/Au). Shearing speed was varied from 0.5 to 3.0 m/s, and tip height from 10 to 135 ${\mu}m$. As experimental results, for the OSP pad, a ductile fracture increased with tip height, and it decreased with shearing speed. In the case of ENIG pad, the ductile fracture increased with the tip height. The tip height of 10 ${\mu}m$ (2% of solder ball diameter) was unsuitable since the fracture mode was mostly pad lift. Shear energy increased with increasing shearing tip height from 10 to 135 ${\mu}m$ for both of OSP and ENIG pads.

• Journal of Power System Engineering
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• v.19 no.3
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• pp.11-15
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• 2015

In this paper, the multi-point hydrogen detection system based on the combination of the hetero-core optical fiber SPR hydrogen tip sensor and interrogator by pseudorandom noise (PN) code correlation reflectometry has been developed. In a light intensity-based experiment with an LED operating at 850 nm, it has been presented that a transmitted loss change of 0.32dB was induced with a response time of 25 s for 4% $H_2$ in $N_2$ in the case of the 25-nm Au, 60-nm $Ta_2O_5$, and 5-nm Pd multi-layers film. The proposed sensor characteristic shows excellent reproducibility in terms of loss level and time response for the in- and out- $H_2$ action. In addition, in the experiment for multi-point hydrogen detection, all sensors show the real-time response for 4% hydrogen adding with reproducible working. As a result, the real-time multi-point hydrogen detection could be realized by means of the combination of interrogating system and hetero-core optical fiber SPR hydrogen tip sensors.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.4
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• pp.361-364
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• 2008

Tips of probe card were fabricated using MEMS technology. P-type silicon wafer with $SiO_2$ layer was used as a substrate for fabricating the probe card. Ni-Cr and Au used as seed layer for electroplating Ni were deposited on the silicon wafer. Line patterns for probing devices were formed on silicon wafer by electroplating Ni through mold which formed by MEMS technology. Bridge structure was formed by wet-etching the silicon substrate. AZ-1512 photoresist was used for protection layer of back side and DNB-H100PL-40 photoresist was used for patterning of the front side. The mold with the thickness of $60{\mu}m$ was also formed using THB-120N photoresist and probe tip with thickness of $50{\mu}m$ was fabricated by electroplating process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.170-170
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• 2004

박막의 접착강도를 측정하기 위하여 수직력과 수평력을 동시에 측정할 수 있는 0.1∼100 N 용량의 2축 로드셀에 기반을 둔 스크레치 테스터를 개발하였다. 반도체용 Si wafer 기판 위에 Au나 Al 등의 금속이 관은 박막으로 증착된 제품을 table에 고정시킨 후, 2축 로드셀(x, z)이 장착된 하중센서의 선단에 Diamond Tip을 장착하여 기판과 박막에 하중(z-axis)을 증가시키면서 동시에 wafer를 x축 방향으로 이동시킨다. 이런 방식으로 시료의 표면을 긁으면 박막이 벗겨져 나가 Diamond Tip이 기판에 닿을 때 서로 다른 경도차에 의해 진동이 발생하게 되고, 이 진동을 Acoustic Emission 센서에서 감지하여 Crack 발생 시점의 Load와 Stroke를 찾아내게 된다.(중략)