결정질 실리콘 태양전지의 Ag 촉매층을 이용한 나노 텍스쳐링 공정에 관한 연구

오병진,여인환,김민영,임동건,Oh, Byoung-Jin,Yeo, In-Hwan,Kim, Min-Young,Lim, Dong-Gun 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.1

In our report a relatively simple process for fast nano-texturing of p-type(100) CZ- silicon surface using silver catalyzed wet chemical etching in aqueous hydrofluoric acid (HF) and hydrogen peroxide solution($H_2O_2$) at room temperature. The wafers were saw-damaged by NaOH(6 wt%) at $60^{\circ}C$ for 150s. To obtain a nano-structured black surface, a thin layer of silver with thickness of 1 - 10 nm was deposited on the surfaces by evaporation system. After this process the samples were etched in HF : $H_2O_2$ : $H_2O$ = 1:5:10 at room temperature for 80s - 220s. Due to the local catalytic of the Ag clusters, this treatment results in the nano-scale texturing on the surface. This resulted in average reflectance values less than 9% after the silver on the surface of the wafers were removed.

Nano-Wear and Friction of Magnetic Recording Hard Disk by Contact Start/Stop Test

Kim, Woo Seok,Hwang, Pyung,Kim, Jang-Kyo Korean Tribology Society 2000 KSTLE International Journal Vol.1 No.1

Nano-wear and friction of carbon overcoated laser-textured and mechanically-textured computer hard disk were characterised after contact start/stop (CSS) wear test. Various analytical and mechanical testing techniques were employed to study the changes in topography, roughness, chemical elements, mechanical properties and friction characteristics of the coating arising from the contact start/stop wear test These techniques include: the atomic force microscopy (AFM), the continuous nano-indentation test, the nano-scratch test, the time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and the auger electron spectroscopy (AES). It was shown that the surface roughness of the laser-textured (LT) bump and mechanically textured (MT) Bone was reduced approximately am and 7nm, respectively, after the CSS wear test. The elastic modulus and hardness values increased after the CSS test, indicating straining hardening of the top coating layer, A critical load was also identified fer adhesion failure between the magnetic layer and the Ni-P layer, The TOF-SIMS analysis also revealed some reduction in the intensity of C and $C_2$$F_59$, confirming the wear of lubricant elements on the coating surface.

고효율 실리콘 태양전지를 위한 lotus surface 구조의 형성

정현철,백용균,김효한,음정현,최균,김형태,장효식,Jung, Hyun-Chul,Paek, Yeong-Kyeun,Kim, Hyo-Han,Eum, Jung-Hyun,Choi, Kyoon,Kim, Hyung-Tae,Chang, Hyo-Sik 한국결정성장학회 2010 韓國結晶成長學會誌 Vol.20 No.1

단결정 실리콘 태양전지의 광학적 손실을 감소시키는 표면 텍스쳐링은 최종 셀의 효율을 향상시키기 위하여 매우 중요하다. 본 연구에서는 2-step texturing의 공정으로 기존의 텍스쳐링에서 이루어진 피라미드에 수 많은 sub-micrometer 사이즈의 구조를 형성시켰다. $AgNO_3$ 용액으로 웨이퍼 표면에 Ag코팅을 한 후, 그 웨이퍼를 다시 HF/$H_2O_2$ 용액으로 수십초 동안 식각을 거치게 된다. 결과적으로, 피라미드 위에 생성된 수 nm사이즈의 구조물들은 $AgNO_3$의 농도 및 식각 시간의 변화에 의해 그 크기와 굵기가 변화하는 것을 알 수 있었다. 웨이퍼의 표면이 2-step texturing에 의해 식각이 이루어지면 연잎의 거친 표면과 비슷해지고, 그 결과 평균 10% 이상의 반사율을 보이던 기존 웨이퍼에서 3% 이하의 낮은 반사율을 얻을 수 있었다. 이는 일반적인 텍스쳐링과 anti-reflection coating을 거친 웨이퍼의 반사율보다 낮은 결과이다. The reduction of optical losses in mono-crystalline silicon solar cell by surface texturing is a critical step to improve the overall cell efficiency. In this study, we have changed the sub-micrometer structure on the micrometer pyramidal structure by 2-step texturing. The Ag particles were coated on the micrometer pyramid surface in $AgNO_3$ solution, and then the etching with hydrogen fluoride and hydrogen peroxide created even smaller nano-pyramids in these pyramids. As a result, we observed that the changes of size and thickness of nano structure on pyramidal surface were determined by $AgNO_3$ concentration and etching time. Using 2-step texturing, the surface of wafers is etched to resemble the rough surface of a lotus leaf. Lotus surface can reduce average reflectance from 10% to below 3%. This reflectance is less than conventional textured wafer including anti-reflection coating.

Effect of Scale and Sequence of Surface Textures on the Anti-adhesive Wear Performance of PVD Coated Tool in Dry Machining SLM-Produced Stainless Steel

Kedong Zhang,Xuhong Guo,Chengdong Wang,Xiangfeng Meng,Lining Sun,Youqiang Xing 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.5

During the dry post-machining processing of selective laser melting (SLM)-produced stainless steel with TiAlN coated tool, the elements of stainless steel chips can diff use and adhere into the coated tool surface, causing serious adhesive wear. In this study, to inhibit the adhesion problem at the tool-chip interface, surface textures with different scales (micro-, nano- and micro/nano-textures) are produced on tool rake face by laser processing before and after physical vapor deposition (PVD) TiAlN coatings deposition. To investigate the cutting performance of these developed coated tools, dry machining tests of the SLM-produced stainless steel are carried out. And, the mechanical properties of textured TiAlN coatings such as the hardness, elastic modulus and critical load are also studied to explain the results from the machining tests. It can be found that the anti-adhesive wear performance of TiAlN coated tool is improved by laser surface texturing. The texture dimension significantly affects the mechanical properties and dry cutting performance of the TiAlN coated tool, and the micro/nanotextures are found to be optimum. Meanwhile, the sequence of surface textures also has an effect on the wear performance of the developed TiAlN coated tools. In the experiment, laser surface texturing before coatings is effective in acting as a barrier against flaking of the TiAlN fi lm, providing a higher active surface for the subsequent TiAlN coatings and presenting a higher compressive residual stress. Thus, the developed cutting tool which is textured before TiAlN coatings deposition presents a milder wear compared to the developed one which is textured after TiAlN coatings deposition.

Induced liquid-solid contact via micro/nano multiscale texture on a surface and its effect on the Leidenfrost temperature

Lee, Gi Cheol,Kang, Jun-young,Park, Hyun Sun,Moriyama, Kiyofumi,Kim, Seol Ha,Kim, Moo Hwan Elsevier 2017 Experimental thermal and fluid science Vol.84 No.-

<P><B>Abstract</B></P> <P>A significant increase in the Leidenfrost temperature (LFT) was observed on a micro/nano multiscale textured surface (MTS) compared with a polished surface (PS) and a micro rough surface (MRS). MTS was fabricated by anodic oxidation and has nano-scaled needles with micro roughness. It showed improved surface wetting characteristics (0° contact angle with liquid spreading). On the other hand, MRS was fabricated by mechanical polishing and it only has micro roughness. LFT on MTS and MRS increased by approximately 150°C and 30°C, respectively, compared with one for PS. The textures on each surface influenced the water droplet dynamics. The relationship between LFT and the dynamics of water droplet were studied by high-speed photography. The key phenomenon determining LFT was the rebound process of the droplet during a few milliseconds. On MRS and MTS, the rebound phenomenon of the droplet was disturbed by the surface-texture-induced liquid-solid contact even when the surface was initially at a high temperature over 300°C. The precursor wetting front, observed only on MTS and the capillary wicking phenomenon are likely the responsible mechanisms that significantly increased LFT on MTS.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heat transfer performance of a droplet on modified surface is evaluated. </LI> <LI> Micro/nano multiscale textured surface (MTS) shows a super-hydrophilic property. </LI> <LI> MTS affects to increase of Leidenfrost temperature up to 465°C. </LI> <LI> The precursor wetting front was observed on MTS, initially heated over than 400°C. </LI> </UL> </P>

다결정 SnSe 열전 재료의 성능 개선 연구 동향

정명준,최병준 한국분말재료학회 2022 한국분말재료학회지 (KPMI) Vol.29 No.2

Thermoelectric materials can reversely convert heat and electricity into each other; therefore, they can be very useful for energy harvesting from heat waste. Among many thermoelectrical materials, SnSe exhibits outstanding thermoelectric performance along the particular direction of a single crystal. However, single-crystal SnSe has poor mechanical properties and thus it is difficult to apply for mass production. Therefore, polycrystalline SnSe materials may be used to replace single-crystal SnSe by overcoming its inferior thermoelectric performance owing to surface oxidation. Considerable efforts are currently focused on enhancing the thermoelectric performance of polycrystalline SnSe. In this study, we briefly review various enhancement methods for SnSe thermoelectric materials, including doping, texturing, and nano-structuring. Finally, we discuss the future prospects of SnSe thermoelectric powder materials.

Dynamic hydrophobicity on flat and pillared graphite surfaces with different pillar surface fractions

Matthew Stanley Ambrosia,하만영,S. Balachandar 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2

The motion of a droplet on a surface is of importance to many fields. While many things are known at the macro-scale still a completeunderstanding of fluid flow at the nano-scale is far from being known. This study focuses on the dynamic hydrophobicity of a pillar surfacewith different pillar surface fractions at the nano-scale using molecular dynamics simulations. Five pillar heights and four pillar surfacefractions were modeled using a graphite surface which has anisotropic characteristics due to its spaced layers. A nano-sized waterdroplet with 5124 molecules was run to equilibrium on each surface. Then a body force was applied and the dynamic contact angles werecalculated for 5 ns. These contact angles were used to calculate the surface’s effective hydrophobicity. The droplets were categorized intoone of three groups as different phenomena were identified depending on the pillar surface fraction, applied force, and pillar height. Itwas found that at the nano-scale smooth, flat surfaces are dynamically more hydrophobic than any of the cases with pillars. Larger pillarsurface fractions tended to be more hydrophobic and the pillar surface fraction of 36% was least affected by pillar height and appliedbody force.

Investigation of Fe-rich fragments in aluminum-steel friction stir welds <i>via</i> simultaneous Transmission Kikuchi Diffraction and EDS

Abbasi, Majid,Dehghani, Morteza,Guim, Hwan-Uk,Kim, Dong-Ik Elsevier 2016 Acta materialia Vol.117 No.-

<P>An attempt has been made to investigate Fe-rich fragments and surrounding intermetallic compounds in aluminum-steel friction stir welds using conventional EBSD + EDS as well as advanced Transmission Kikuchi Diffraction (TKD). Results indicate that the fragments are covered by a layer of orthorhombic Al5Fe2. This layer is surrounded by a mixed region composed of sub-micrometer Al3Fe crystals in a matrix of Al nano grains. Employing high beam current TKD on electron-transparent samples enables investigation of sub-micrometer grains in the mixed region with a higher spatial resolution than conventional EBSD. As a result, nano-twinning in Al in the mixed region has been observed. Microstructural and texture results imply that Fe-rich fragments travel through the Al matrix under extreme shear forces, severely refining Al grains, and inducing nano-twinning. Due to extreme shear forces and Fe outward diffusion, fine steel fragments dissolve in the surroundings leading to the nucleation of nano Al3Fe crystals particularly along Al grain boundaries. Al3Fe crystals consume the Al matrix as they grow in size and fraction. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.</P>

Periodic Nano-textured Patterns on Biomaterial by Femtosecond Laser Ablation to Regulate Cell Behaviors

김새로미,정용우,김경수,전인동,옥명렬,김유찬,석현광,전호정 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.5

Nano-textured Micro Patterning on Intraocular Lens to Suppress Posterior Capsular Opacification by Regulating Lens Epithelial Cells

Youngmin Seo(서영민),Kyungwoo Lee(이경우),Byoung Chan Choi(최병찬),Choun-Ki Joo(주천기),Hojeong Jeon(전호정) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11