• 한국결정성장학회지
• /
• 제21권3호
• /
• pp.114-118
• /
• 2011

본 논문에서는 육각형 GaN 피라미드의 꼭지점 부분에만 나노 혹은 마이크로 크기의 GaN 구조를 선택적으로 성장시킬 수 있는 결정 성장 방볍에 대하여 연구하였다. 최적화된 포토리소그라피 공정을 이용하여 육각형 GaN 피라미드 구조의 꼭지점 부분의 $SiO_2$ 마스크 영역만을 제거할 수 있었으며, 이렇게 하여 노출된 육각형 GaN 피라미드의 꼭지점 부분에만 metal organic vapor phase epitaxy(MOVPE) 결정 성장방법을 사용하여 나노 및 마이크로 크기의 GaN 구조를 선택적으로 성장하였다. GaN 피라미드 꼭지점 부근에 형성된 나노 및 마이크로 G값J 구조는 semi-polar {1-101} 결정면으로 둘러싸인 육각 피라미드 형상을 하고 있으며 그들의 크기는 성장 시간에 의해 쉽게 조절할 수 있음을 확인하였다. TEM 관측 결과, 측면 방향으로 진행하는 관통전위들이 $SiO_2$ 마스크에 의해 효율적으로 차단되어 나노 및 마이크로 GaN 구조에서는 전위 밀도가 감소하는 것을 확인할 수 있었으나 $SiO_2$ 마스크의 끝부분의 매끄럽지 못한 부분에 의해 적층 결함이 발생함을 확인하였다.

• International Journal of Precision Engineering and Manufacturing
• /
• 제8권4호
• /
• pp.63-69
• /
• 2007

The two-photon stereolithography (TPS) process is a promising technique for the fabrication of real three-dimensional (3D) nano/micro-structures via application of a femto-second laser, In TPS, when a near-infrared ultrashort-pulsed laser is closely focused onto a confined volume of photocurable resin, only the local area at the center of the focus is cured. Therefore, real 3D microstructures with resolution under the diffraction limit can be fabricated through a layer-by-layer accumulative technique, This process provides opportunities to develop neo-conceptive nano/micro devices in IT/BT industries, However, a number of issues, including development of effective fabrication methods, highly sensitive and functional materials, and neo-conceptive devices using TPS, must be addressed for the realization of industrial application of TPS. In this review article, we discuss our efforts related to TPS: effective fabrication methods, diverse two-photon curable materials for high functional devices, and applications.

• 대한기계학회논문집A
• /
• 제29권7호
• /
• pp.998-1004
• /
• 2005

A nano-stereolithography (NSL) process has been developed for fabrication of 3D shell structures which can be applied to various nano/micro-fluidic devices. By the process, a complicated 3D shell structure on a scale of several microns can be fabricated using lamination of layers with a resolution of 150 nm in size, so it does not require the use of my sacrificial layer or any supporting structure. A layer was fabricated by means of solidifying liquid-state monomers using two-photon absorption (TPA) induced using a femtosecond laser processing. When the polymerization process is finished, unsolidified liquid state resins can be removed easily by dropping several droplets of ethanol fur developing the fabricated structure. Through this work, some 3D shell structures, which can be applied to various applications such as nano/micro-fluidic devices and MEMS system, were fabricated using the developed process.

• 대한기계학회논문집A
• /
• 제33권11호
• /
• pp.1209-1216
• /
• 2009

Nano-micro hierarchical structures that nanoprotrusions were formed on the network-type microstructures were fabricated using an ultrasonic vibration forming technology. A commercial ultrasonic welding system was used to apply ultrasonic vibration energy. To evaluate the formability of ultrasonic vibration forming, nickel nano-micro hierarchical mold was fabricated and polyethylene (PE) was used as the replication material. The optimal molding time was 3.5 sec for PE nano-micro hierarchical structures. The molding process was conducted at atmospheric pressure.

• 한국표면공학회지
• /
• 제45권4호
• /
• pp.151-154
• /
• 2012

A hydrophobic surface has been fabricated on aluminum by two-step surface treatment processes consisting of structure modification and surface coating. Nature inspired micro nano scale structures were artificially created on the aluminum surface by a blasting and Ar ion beam etching. And a hydrophobic thin film was coated by a trimethylsilane ($(CH_3)_3SiH$) plasma deposition to minimize the surface energy of the micro nano structure surface. The contact angle of micro nano structured aluminum surface with the trimethylsilane coating was $123^{\circ}$ (surface energy: 9.05 $mJ/m^2$), but the contact angle of only trimethylsilane coated sample without the micro nano surface structure was $92^{\circ}$ (surface energy: 99.15 $mJ/m^2$). In the hydrophobic treatment of aluminum surface, a trimethylsilane coated sample having the micro nano structure was more effective than only trimethylsilane coated sample without the micro nano structure.

• Journal of Ceramic Processing Research
• /
• 제13권spc1호
• /
• pp.93-95
• /
• 2012

We report on the growth and characterization of the nano- and micro scale GaN structures selectively grown on the vertex of GaN stripes using the metal organic vapor phase epitaxy method and conventional photolithography technique. The triangular shaped nano- and micro GaN structures which have semi-polar {11-22} facets were formed only on the vertex of the lower GaN stripes. Crystalline defects reduction was observed by transmission electron microscopy for upper GaN stripes. We also have grown the InGaN/GaN multi-quantum well structures on the semi-polar facets of the upper GaN stripes. Cathodoluminescence images were taken at 366, 412 and 555 nm related to GaN band edge, InGaN/GaN layer and defects, respectively.

• 한국분말재료학회지
• /
• 제20권5호
• /
• pp.355-358
• /
• 2013

Micro trench structures are applied in gratings, security films, wave guides, and micro fluidics. These micro trench structures have commonly been fabricated by micro electro mechanical system (MEMS) process. However, if the micro trench structures are machined using a diamond tool on large area plate, the resulting process is the most effective manufacturing method for products with high quality surfaces and outstanding optical characteristics. A nonferrous metal has been used as a workpiece; recently, and hybrid materials, including polymer materials, have been applied to mold for display fields. Thus, the machining characteristics of polymer materials should be analyzed. In this study, machining characteristics were compared between nonferrous metals and polymer materials using single crystal diamond (SCD) tools; the use of such materials is increasing in machining applications. The experiment was conducted using a square type diamond tool and a shaper machine tool with cutting depths of 2, 4, 6 and 10 ${\mu}m$ and a cutting speed of 200 mm/s. The machined surfaces, chip, and cutting force were compared through the experiment.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.1927-1931
• /
• 2003

Nanometer-sized structures are being applied to many fields including micro/nano electronics, optoelectronics, quantum computing, biosensors, etc. Micro contact printing is one of the most promising methods for manufacturing the nanometer-sized structures. The crucial element for the micro contact printing is the nano-resolution printing technique using polymeric stamps. In this study, a multi-scale analysis scheme for simulating the micro contact printing process is proposed and some useful analysis results are presented. Using the slip-link model [1], the dependency of viscoelasticity on molecular weight of polymer stamp is predicted. Deformation behaviors of polymeric stamps are analyzed using finite element method based upon the predicted viscoelastic properties.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2004년도 Proceedings of 2004 Korea-Japan Joint Seminar on Particle Image Velocimetry
• /
• pp.75-80
• /
• 2004

Aerospike nozzles have been expected to be used for an engine of a reusable space shuttle to respond to growing demand for rocket-launching and its cost reduction. In this study, the flow field structures in any cross sections around clustered linear aerospike nozzles are visualized and analyzed, using laser induced fluorescence (LIF) of nitrogen monoxide seeded in the carrier gas of nitrogen. Since flow field structures are affected mainly by pressure ratio, the clustered linear aerospike nozzle is set inside a vacuum chamber to carry out the experiments in the wide range of pressure ratios from 75 to 200. Flow fields are visualized in several cross-sections, demonstrating the complicated three-dimensional flow field structures. Pressure sensitive paint (PSP) of PtTFPP bound by poly- IBM -co-TFEM is also applied to measurement of the complicated pressure distribution on the spike surface, and to verification of contribution of a truncation plane to the thrust. Finally, to examine the effect of the sidewalls attached to the aerospike nozzle, the flow fields around the nozzle with the sidewalls are compared with those without sidewalls.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.144-149
• /
• 2004

Porous anodic alumina has been used widely for corrosion protection of aluminum surfaces or as dielectric material in micro-electronics applications. It exhibits a homogeneous morphology of parallel pores which can easily be controlled between 10 and 400nm. It has been applied as a template for fabrication of the nanometerscale composite. In this study, mechanical properties of the AAO structures are measured by the nano indentation method. Nano indentation technique is one of the most effective method to measure the mechanical properties of nano-structures. Basically, hardness and elastic modulus can be obtained by the nano-indentation. Using the nano-indentation method, we investigated the mechanical properties of the AAO structure with different size of nano-holes. In results, we find the hole effect that changes the mechanical properties as size of nano hole.