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The influence of contact material on lateral wet-etching of nickel thin films in lamellae structure
Kim, Jeong Hwan,Jeong, Jik-Han,Lee, Seung-Hun,Kim, Kwanoh,Yoon, Jae Sung,Choi, Doo-Sun,Yoo, Yeong-Eun Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-
<P><B>Abstract</B></P> <P>The characteristics of lateral Ni film etching by nitric-acid-based etchant are examined using samples with patterned lamellar layers consisting of SiO<SUB>2</SUB>/Ni/Al<SUB>2</SUB>O<SUB>3</SUB>/Ni/Al<SUB>2</SUB>O<SUB>3</SUB> toward the fabrication of hierarchical structures. The lateral etching length increased with increasing etching time, despite the difficult penetration of the etchant through the nanoscale passages in the lamellar layers. However, a higher etching rate (2.1 nm s<SUP>−1</SUP>) was observed in the lower Ni film that is in contact with SiO<SUB>2</SUB> and Al<SUB>2</SUB>O<SUB>3</SUB> layers on the bottom and top, respectively, compared to that (1.6 nm s<SUP>−1</SUP>) of the upper Ni film that contacts with only Al<SUB>2</SUB>O<SUB>3</SUB> on both bottom and top sides, due to stronger wetting of SiO<SUB>2</SUB>, inducing easier penetration of the etchant into the nanoscale passage between the surrounding layers. Moreover, the influence of Ni film thickness on the lateral etching characteristic was also investigated. The difference in the lateral etching length of the upper and lower Ni films decreases when the Ni film thickness is increased, because of the reduced proportion of the interface region with respect to the Ni-film volume. Despite different contact materials, similar lateral etching lengths were observed in the 150-nm-thick Ni films due to negligible effect of the contact materials in the lamellar structure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Lateral Ni film etching characteristics by nitric-acid-based etchant are investigated. </LI> <LI> Lateral film etching rate via nanoscale passage varies depending on contact materials. </LI> <LI> Difference in lateral etching length decreases when Ni film thickness is increased. </LI> <LI> Similar lateral etching lengths were observed in the 150 nm-thick Ni films. </LI> </UL> </P>
Frequency Tuning of Nanowire Resonator Using Electrostatic Spring Effect
Jihan Kwon,Jungwook Choi,Kwanoh Kim,Jaesam Sim,Jinho Kim,Jongbaeg Kim IEEE 2009 IEEE transactions on magnetics Vol.45 No.5
<P>We have demonstrated resonant frequency tuning of nanowire resonator operated in both atmospheric circumstance and high vacuum environment using electrostatic spring-softening effect. The nanowire is synthesized at any desired position by focused ion beam-chemical vapor deposition (FIB-CVD) on the sidewall of batch-processed micro electrode. The resonant frequency in a vacuum chamber of 2.5 x 10(-4) Pa is 1.564 MHz under the driving voltage of 5 V-DC +/- 5 V-AC. When 30 VDC tuning bias is applied on tuning electrode, the resonant frequency is reduced to 1.529 MHz due to the electrostatic spring-softening effect while the driving bias is maintained. For the tuning bias of 60 V, the resonant frequency at atmospheric pressure has been tuned from 1.49 MHz to 1.41 MHz under the driving voltage of 30V(DC) +/- 10V(AC). The method demonstrated both in high vacuum and at atmospheric pressure is a simple and effective way to tune the deviated resonant frequency of nanowire resonator to the desired value without the alteration of the structure or post fabrication process.</P>
전자빔 증발법 박막 증착을 이용한 양극 산화 알루미늄 템플릿의 나노 포어 가공 연구
이승훈(Seung-Hun Lee),이민영(Minyoung Lee),김천중(Chunjoong Kim),김관오(Kwanoh Kim),윤재성(Jae Sung Yoon),유영은(Yeong-Eun Yoo),김정환(Jeong Hwan Kim) 한국표면공학회 2021 한국표면공학회지 Vol.54 No.1
The fabrication of nanopore membrane by deposition of Al₂O₃ film using electron-beam evaporation, which is fast, cost-effective, and negligible dependency on substance material, is investigated for potential applications in water purification and sensors. The decreased nanopore diameter owing to increased wall thickness is observed when Al₂O₃ film is deposited on anodic aluminum oxide membrane at higher deposition rate, although the evaporation process is generally known to induce a directional film deposition leading to the negligible change of pore diameter and wall thickness. This behavior can be attributed to the collision of evaporated Al₂O₃ particles by the decreased mean free path at higher deposition rate condition, resulting in the accumulation of Al₂O₃ materials on both the surface and the edge of the wall. The reduction of nanopore diameter by Al₂O₃ film deposition can be applied to the nanopore membrane fabrication with sub-100 nm pore diameter.
Suspended GaN nanowires as NO<sub>2</sub> sensor for high temperature applications
Sim, Jaesam,Kim, Kwanoh,Song, Soonho,Kim, Jongbaeg The Royal Society of Chemistry 2013 The Analyst Vol.138 No.8
<P>We propose a gas sensor operable over a wide temperature range and using suspended GaN nanowires functionalized with Pt–Pd. The sensor is batch-fabricated by directly integrating the GaN nanowires onto batch-processed silicon microelectrodes in parallel. The high thermal stability of the sensor originates from a large band gap of GaN nanowires that enables the detection of NO<SUB>2</SUB> gas at an elevated temperature of up to 350 °C without a decrease in responsiveness. Exposed to NO<SUB>2</SUB> at 100–1000 ppm at 350 °C, the sensor shows a linear increment in relative response with respect to the change in gas concentration. The sensor results in a two- to four-fold increase in responsiveness to NO<SUB>2</SUB> at 100 ppm compared to NH<SUB>3</SUB> at 100 ppm and CO<SUB>2</SUB> at 1000 ppm. The nanowires suspended over a substrate provide increased surface area that could interact with gas molecules for enhanced responsiveness, and prevent any unnecessary interactions between the nanowires and the substrate.</P> <P>Graphic Abstract</P><P>We propose a gas sensor operable over a wide temperature range and using suspended GaN nanowires functionalized with Pt–Pd. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3an36917j'> </P>
Nguyen Hoang Minh,Kwanoh Kim,Do Hyun Kang,Yeong-Eun Yoo,Jae Sung Yoon 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Wearable sensors that monitor human activities such as strain, pressure and temperature are the next frontier in personalized healthcare. Despite of recent research on wearable sensor, especially, strain sensor, a device with simplicity in structure and in fabrication process has not yet been well commercialized. In this study, we report a strain sensor based on nano-bump arrays on polydimethylsiloxane (PDMS) substrate. A reusable mold with nano-concave structure is facilely fabricated by colloidal lithography. The nano-bump patterns are then transferred onto the PDMS by replication. Due to diffraction of incident light on nano-patterns, the sensors appear with vivid color. Thus, stretching the sensor up to 50% leads to the shift of color from blue to red, which covers all visible spectrum. This report is expected to further contribute to the development of colorimetric strain sensor for various applications, such as health care, soft robotics, and prosthetic devices.