• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 제35회 춘계학술대회
• /
• pp.40-44
• /
• 2002

The motivation of this work is to use SAM(Self-Assembled Monolayer) for developing a rapid and flexible non-photolithographic nano-structure fabrication technique which can be utilized in micro-machining of metals as well as silicon-based materials. The fabrication technique implemented in this work consists of a two-step process, namely, mechanical scribing followed by chemical etching. From the experimental results, it was found that thiol on copper surface could be removed even under a few nN normal load. The nano-tribological characteristics of thiol-SAM on various metals were largely dependent on the native oxide layer of metals. Based on these findings, nano-patterns with sub-micrometer width and depth on metal surfaces such as Cu, Au and Ag could be obtained using a diamond-coated tip.

• Tribology and Lubricants
• /
• 제19권2호
• /
• pp.109-115
• /
• 2003

Nanotribological characteristics between a Si$_3$N$_4$ AFM tip and hydrophobic thin films were experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM (atomic force microscope) and LFM (lateral force microscope) modes in various .ranges of normal load. Plasma-modified thin polymeric films were deposited on Si-wafer (100). Results showed that wetting angle of plasma-modified thin polymeric film increased with the treating time, which resulted in the hydrophobic surface and the decrease of adhesion and friction. Nanotribological characteristics of these surfaces were compared with those of other hydrophobic surfaces, such as DLC, OTS and IBAD-Ag coated surfaces. Those of OTS coated surface were superior to those of others, though wetting angle of plasma-modified thin polymeric film is higher.

• Tribology and Lubricants
• /
• 제18권4호
• /
• pp.267-272
• /
• 2002

Nano adhesion between SPM(scanning probe microscope) tips and DDPO$_4$(octadecylphosphoric acid ester.) and ODPO$_4$(octadecylphosphoric acid ester) SAM(self-assembled monolayer.) was experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM(atomic force microscope) and LFM(lateral force microscope) modes with the applied normal load. DDPO$_4$ and ODPO$_4$ SAM were formed on Ti and TiOx surfaces. Ti and TiOx were coated on the Si wafer by ion sputtering. Adhesion and friction of DDPO$_4$ and ODPO$_4$ SAM surfaces were compared with those of OTS(octadecyltrichlorosilane) SAM and DLC surfaces. DDPO$_4$ and ODPO$_4$ SAM converted the Ti and TiOx surfaces to be hydrophobic. When the surface was hydrophobic, the adhesion and friction forces were found lower than those of bare surfaces. Work of adhesion was also discussed to explain how the surface was converted into hydrophobic Results also showed that tribological characteristics of DDPO$_4$ and ODPO$_4$ SAM had good properties in the adhesion, friction, wetting angle and work of adhesion. DDPO$_4$ and ODPO$_4$ SAM could be one of the candidates for the bio-MEMS elements.

• Tribology and Lubricants
• /
• 제18권1호
• /
• pp.1-8
• /
• 2002

Nano adhesion and friction between a $Si_{3}N_{4}$ AFM(atomic force microscope) tip and thin silver films were experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM and LFM(lateral force microscope) modes in various range of normal loads. Thin silver films deposited by IBAD (ion beam assisted deposition) on Si-wafer (100) and other Si-wafers of different surface roughness were used. Results showed that nano adhesion and friction decreased with the surface roughness. When the Si surfaces were coated by pure silver, the adhesion and friction decreased. But the adhesion and friction were not affected by the thickness of IBAD silver coating. As the normal force increased, the adhesion forces of bare Si-wafer and IBAD silver coating film remained constant, but the friction forces increased linearly. Test results suggested that the friction was mainly governed by the adhesion as long as the load was low.

• 한국표면공학회지
• /
• 제29권5호
• /
• pp.314-324
• /
• 1996

Scanning probe microscopes (SPMs) such as the scanning tunneling microscope (STM) and the atomic force microscope (AFM) were used for surface modification tools at the nanometer scale. Material surfaces, i. e., titanium, hydrogen-terminated silicon and trimethylsilyl organosilane monolayer on silicon, were locally oxidized with the best lateral spatial resolution of 20nm. The principle behind this proximal probe oxidation method is scanning probe anodization, that is, the SPM tip-sample junction connected through a water column acting as a minute electrochemical cell. An SPM-nanolithogrphy process was demonstrated using the organosilane monolayer as a resist. Area-selective chemical modifications, i. e., etching, electroless plating with gold, monolayer deposition and immobilization of latex nanoparticles; were achieved in nano-scale resolution. The area-selectivity was based on the differences in chemical properties between the SPM-modified and unmodified regions.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2001년도 제34회 추계학술대회 개최
• /
• pp.35-42
• /
• 2001

Nanotribological characteristics between a Si$_3$N$_4$ AFM tip and hydrophobic thin films were experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM(atomic force microscope) and LFM(lateral force microscope) modes in various ranges of normal load. Plasma-modified thin polymeric films were deposited on Si-wafer (100). Results showed that wetting angle of plasma-modified thin polymeric film increased with the treating time, which resulted in the hydrophobic surface and the decrease of adhesion and friction. Nanotribological characteristics of these surfaces were compared with those of other hydrophobic surfaces, such as DLC, OTS and IBAD-Ag coated surfaces. Those of OTS coated surface was superior to those of others, though wetting angle of plasma-modified thin polymeric film is higher.

• Tribology and Lubricants
• /
• 제25권2호
• /
• pp.81-85
• /
• 2009

Interests in micro/nano-particles have been greatly increasing due to their wide applications in various fields such as environmental and medical sciences as well as engineering. In order to obtain a fundamental understanding of the tribological characteristics at particle-surface contact interface, frictional behaviors according to load/pressure and materials were obtained by using atomic force microscope(AFM) cantilevers with different stiffnesses and tips. Lateral contact stiffnesses were observed in various tip-surface contact situations. Experimental results show that stick-slip friction behavior occurs even when the colloidal probes with a particle of a few micrometers in diameter, which have a relatively large contact area and lack a well-shaped apex, were used. This indicates that atomic stick-slip friction may be a more common phenomenon than it is currently thought to be. Also, experimental results were investigated by considering the competition between the stiffness of the interatomic potential across the interface and the elastic stiffnesses of the contacting materials and the force sensor itself.

• 대한화장품학회지
• /
• 제38권2호
• /
• pp.139-145
• /
• 2012

모발표면에는 독특한 형태의 지방산이 있다. 18-methyleicosanoic acid (18-MEA)는 모발 큐티클의 최외각 층에 공유결합된 특이한 ante-iso 형태의 지방산이다. 18-MEA 층은 CMC의 ${\beta}$-층 위에 위치하면서 모발의 외부 표면에 표면에너지와 마찰저항 을 낮춰준다. 18-MEA 분자의 높은 유동성은 계면 전단력을 감소시켜 외부로부터 전달되는 지질들이 쉽게 퍼지도록 한다. 본 연구에서는 C10 - 40 isoalkyl acid의 말단에 관능기로 N-hydroxyl succinimidyl ester를 도입하여 모발 표면의 공유결합 지방산 층을 회복시켜보고 자 하였다. 모발 표면의 재 소수화를 확인하기 위하여 접촉각을 측정하였다. 서로 다른 습도 조건(40, 55, 70 %RH)에서 모발의 내부 수 분 함유량은 전자 수분 분석기를 이용하여 실시하였다. Hydroxysuccinimidyl C10 - 40 Isoalkyl Acidate (HCIA)로 처리한 모발의 표면은 큐티클을 접착하는 것과 같이 지방산 단분자층이 공유결합을 형성하여 큐티클의 균열을 채워줌으로써 매끄럽고 균일할 것으로 생각되었다. 이러한 접착 효과는 atomic force microscope (AFM) 영상의 라인 프로필(line profile)을 통해서 확인되었다. 따라서 모발 내부 구 성 물질과 수분이 쉽게 용출되지 않고, 외기의 습도가 변하는 경우에도 최적의 모발 습도가 항상 유지된다. AFM을 사용한 lateral force microscopy (LFM) 결과에 따르면 HCIA를 처리한 모발 표면의 마찰력이 감소되었고, 이에 대해 15회 샴푸 과정을 수행한 이후에도 동일한 마찰력 값을 나타내었다.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 제35회 춘계학술대회
• /
• pp.207-214
• /
• 2002

Nano adhesion between SPM (scanning probe microscope) tips and $DDPO_{4}$ (dodecylphosphoric acid ester) and $ODPO_{4}$ (octadecylphosphoric acid ester) SAM (self-assembled monolayer) was experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM(atomic force microscope) and LFM(lateral force microscope) modes with the applied normal load. $DDPO_{4}$ and $ODPO_{4}$ SAM were formed on TiMe and TiOx surfaces. TiMe and TiOx were coated on the Si wafer by ion sputtering. Adhesion and friction of $DDPO_{4}$ and $ODPO_{4}$ SAM surfaces were compared with those of OTS (octadecyltrichlorosilane) SAM and DLC surfaces. $DDPO_{4}$ and $ODPO_{4}$ SAM converted the TiMe and TiOx surfaces to be hydrophobic. When the surface was hydrophobic, the adhesion and friction forces were found lower than those of bare surfaces. Work of adhesion was also discussed to explain how the surface was converted into hydrophobic. Results also showed that tribological characteristics of $DDPO_{4}$ and $ODPO_{4}$ had good properties in the adhesion, friction, wetting angle and work of adhesion. $DDPO_{4}$ and $ODPO_{4}$ SAM could be one of the candidates for the bio-MEMS elements.

• 한국재료학회지
• /
• 제15권10호
• /
• pp.626-631
• /
• 2005

GaN-related compound semiconductors were grown on the corrugated interface substrate using a metalorganic chemical vapor deposition system to increase the optical power of white LEDs. The patterning of substrate for enhancing the extraction efficiency was processed using an inductively coupled plasma reactive ion etching system and the surface morphology of the etched sapphire wafer and that of the non-etched surface were investigated using an atomic force microscope. The structural and optical properties of GaN grown on the corrugated interface substrate were characterized by a high-resolution x-ray diffraction, transmission electron microscopy, atomic force microscope and photoluminescence. The roughness of the etched sapphire wafer was higher than that of the non-etched one. The surface of III-nitride films grown on the hemispherically patterned wafer showed the nano-sized pin-holes that were not grown partially. In this case, the leakage current of the LED chip at the reverse bias was abruptly increased. The reason is that the hemispherically patterned region doesn't have (0001) plane that is favor for GaN growth. The lateral growth of the GaN layer grown on (0001) plane located in between the patterns was enhanced by raising the growth temperature ana lowering the reactor pressure resulting in the smooth surface over the patterned region. The crystal quality of GaN on the patterned substrate was also similar with that of GaN on the conventional substrate and no defect was detected in the interface. The optical power of the LED on the patterned substrate was $14\%$ higher than that on the conventional substrate due to the increased extraction efficiency.