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Ju, Seongmin,Linganna, Kadathala,Kim, Bok Hyeon,Boo, Seongjae,An, Yong Ho,Han, Won-Taek American Scientific Publishers 2018 Journal of Nanoscience and Nanotechnology Vol.18 No.3
<P>Alumino-germano-silicate glass optical fiber incorporated with Gd2O3 nano-particles (NPs) was developed by using the modified chemical vapor deposition and the drawing process. The formation of spherical Gd2O3 NPs in the fiber core with average diameter of 10.8 nm was confirmed by the TEM. The distinct absorption peaks in the fiber preform appearing in the UV region at 205, 247, 253, 274, and 312 nm were due to the incorporated Gd2O3 NPs via reorganization of the seven 4f electrons into various multiplets of Gd ions. In the case of the optical fiber obtained by drawing of the preform at high temperature about 2150 degrees C, absorption peaks due to Gd2O3 NPs were found to appear at 383 and 455 nm, which were red-shifted from 274 and 312 nm of the preform, respectively, and it may be due to increase in the size of Gd2O3 NPs after the drawing process. To investigate the photoluminescence (PL) property for UV sensor applications, the PL of the fiber was obtained by illumination of the Xenon-lamp. A PL band appeared in the wavelength band from 370 nm to 450 nm, centering at about 400 nm, which can be attributed to the presence of Gd2O3 NPs embedded in the fiber core. It was also found that the PL intensity at 400 nm showed linear dependence with the excitation power from 0 to 400 W.</P>
Seongmin Ju,Seongmook Jeong,Youngwoong Kim,Watekar, Pramod Ramdasrao,Won-Taek Han IEEE 2013 Journal of lightwave technology Vol.31 No.16
<P>A novel all-optical fiber isolator with 14 dB isolation at 660 nm was demonstrated using the CdSe quantum dots doped optical fiber, which was fabricated by using the modified chemical vapor deposition and high temperature drawing processes. The Faraday rotation angle of 45 degrees was obtained at the fiber length of 183 cm under the magnetic field of 0.119 T.</P>
Fabrication and Optical Characteristics of a Novel Optical Fiber Doped with the Au Nanoparticles
Ju, Seongmin,Nguyen, Viet Linh,Watekar, Pramod R.,Kim, Bok Hyeon,Jeong, Chaehwan,Boo, Seongjae,Kim, Cheol Jin,Han, Won-Taek American Scientific Publishers 2006 Journal of Nanoscience and Nanotechnology Vol.6 No.11
<P>Optical fibers containing gold metal nanoparticles were developed by modified chemical vapor deposition, in which Au(OH)3 and tetraethyl-orthosilicate (TEOS) was used via sol-gel process to incorporate gold metals by providing the reduction atmosphere. The absorption peak appeared near 490 nm was found to be due to the surface plasmon resonance of the gold nanoparticles incorporated in the fiber core.</P>
Ju, Seongmin,Watekar, Pramod R,Han, Won-Taek Optical Society of America 2011 Optics express Vol.19 No.3
<P>Germano-silicate glass optical fiber incorporated with PbTe semiconductor quantum dots (SQDs) in the core was fabricated by using the atomization process in modified chemical vapor deposition (MCVD) process. The absorption bands attributed to PbTe semiconductor quantum dots in the fiber core were found to appear at around 687 nm and 1055 nm. The nonlinear refractive index measured by the long-period fiber grating (LPG) pair method upon pumping with laser diode at 976.4 nm was estimated to be ~1.5 × 10<sup>-16</sup> m<sup>2</sup>/W.</P>
Ju, Seongmin,Watekar, Pramod Ramdasrao,Han, Won-Taek IEEE 2010 Journal of Lightwave Technology Vol.28 No.18
<P>We developed and demonstrated a highly sensitive fiber Bragg grating (FBG) temperature sensor by using the PbO-GeO <TEX>$_{2}$</TEX>-SiO <TEX>$_{2}$</TEX> glass optical fiber. Temperature sensitivity of the FBG sensor based on the PbO-GeO <TEX>$_{2}$</TEX>-SiO <TEX>$_{2}$</TEX> glass optical fiber was about 40% improved to the 0.0173 nm/<TEX>$^{\circ}$</TEX> C by the thermal expansion increase of the fiber.</P>
Ju, Seongmin,Jeong, Seongmook,Kim, Youngwoong,Lee, Sang-Hyun,Han, Won-Taek American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.6
<P>A novel surface plasmon resonance (SPR) sensor based on specialty optical fiber having its cladding doped with Au nano-particles (NPs) was developed by modified chemical vapor deposition process. To optimize the SPR absorption and sensitivity of the fiber SPR sensor, effect of the fiber length (20 cm-90 cm) on sensing capability of refractive index (n = 1.418-1.448) was investigated. Absorption peaks appearing at 392 and 790 nm were due to SPR from Au NPs in the cladding region of the optical fiber. The SPR was found to occur at particular wavelengths around 390 nm for the corresponding refractive indices regardless of the length of the fiber, increased with the increase of the index. The measured SPR sensitivities (wavelength/RIU) of the fiber were estimated to be 407 nm/RIU, 217 nm/RIU, and 54 nm/RIU with the fiber lengths of 20 cm, 45 cm, and 90 cm, respectively. The SPR absorption intensity and FWHM decreased with the increase of the fiber length because the propagation loss of the signal through the fiber cladding region increased.</P>
박성민 ( Seongmin Park ),홍석주 ( Suk-ju Hong ),조철훈 ( Cheorun Jo ),김기석 ( Ghiseok Kim ) 한국농업기계학회 2022 한국농업기계학회 학술발표논문집 Vol.27 No.2
품질 인증의 목적으로 육류의 상태를 빠르게 파악하기 위해서는 재현성과 정확성이 높은 기술이 필요한데, 근적외선 분광법은 이러한 요구를 만족시킬 수 있다. 근적외선 초분광 데이터를 이용하여 비파괴 방식으로 소고기 시료의 보관 상태를 구분하는 모델을 개발하였다. 소고기를 일정한 조건 하에서 냉장 또는 냉동 보관하면서 15일에 걸쳐 신선한 상태, 오래된 냉장 상태, 냉동 후 해동된 상태의 데이터를 획득하였다. 이 과정에서 근적외선 초분광 데이터 큐브를 획득하였으며, 시료의 상태를 정량적으로 파악하기 위해 전통적 품질 인자인 육즙감량 값에 대한 실험을 동시에 수행하였다. 데이터 정제를 통해 약 5,000개의 근적외선 스펙트럼을 추출하였으며 5가지 전처리 기법을 적용한 후 PLS-DA와 SVM 기법을 적용하여 모델을 개발하였다. 성능 평가 지표로는 기본적으로 정확도를 사용하였고, 신선육 판정에 대한 성능을 따로 확인하기 위해 ‘신선’ 그룹에 대한 F1 score를 추가로 계산하였다. 마지막 과정으로는 이러한 실험 과정을 반복하여, 검증에 필요한 verification set 데이터를 만들고 개발된 모든 모델에 적용하여 해당 모델의 범용성을 평가하였다. 개발 결과 초분광 데이터 큐브를 정제하여 스펙트럼을 선별하고 예측 모델을 개발하면 신선육과 그렇지 않은 것을 구분할 수 있다는 결론을 얻었다.
Oxygen plasma exposure effects on indium oxide nanowire transistors
Kim, Seongmin,Delker, Collin,Chen, Pochiang,Zhou, Chongwu,Ju, Sanghyun,Janes, David B IOP Pub 2010 Nanotechnology Vol.21 No.14
<P>In<SUB>2</SUB>O<SUB>3</SUB> nanowire transistors are fabricated with and without oxygen plasma exposure of various regions of the nanowire. In two-terminal devices, exposure of the channel region results in an increased conductance of the channel region. For In<SUB>2</SUB>O<SUB>3</SUB> nanowire transistors in which the source/drain regions are exposed to oxygen plasma, the mobility, on–off current ratio and subthreshold slope, are improved with respect to those of non-exposed devices. Simulations using a two-dimensional device simulator (MEDICI) show that improved device performance can be quantified in terms of changes in interfacial trap, shifts in fixed charge densities and the corresponding reduction in Schottky barrier height at the contacts. </P>
Kim, Seongmin,Kim, Hwansoo,Janes, David B,Ju, Sanghyun IOP Pub 2013 Nanotechnology Vol.24 No.30
<P>Due to the large surface-to-volume ratio of nanowires, the quality of nanowire–insulator interfaces as well as the nanowire surface characteristics significantly influence the electrical characteristics of nanowire transistors (NWTs). To improve the electrical characteristics by doping or post-processing, it is important to evaluate the interface characteristics and stability of NWTs. In this study, we have synthesized ZnSnO (ZTO) nanowires using the chemical vapor deposition method, characterized the composition of ZTO nanowires using x-ray photoelectron spectroscopy, and fabricated ZTO NWTs. We have characterized the current–voltage characteristics and low-frequency noise of ZTO NWTs in order to investigate the effects of interface states on subthreshold slope (SS) and the noise before and after N<SUB>2</SUB> plasma treatments. The as-fabricated device exhibited a SS of 0.29 V/dec and Hooge parameter of ∼1.20 × 10<SUP>−2</SUP>. Upon N<SUB>2</SUB> plasma treatment with N<SUB>2</SUB> gas flow rate of 40 sccm (20 sccm), the SS improved to 0.12 V/dec (0.21 V/dec) and the Hooge parameter decreased to ∼4.99 × 10<SUP>−3</SUP> (8.14 × 10<SUP>−3</SUP>). The interface trap densities inferred from both SS and low-frequency noise decrease upon plasma treatment, with the highest flow rate yielding the smallest trap density. These results demonstrate that the N<SUB>2</SUB> plasma treatment decreases the interface trap states and defects on ZTO nanowires, thereby enabling the fabrication of high-quality nanowire interfaces.</P>
Selective Contact Anneal Effects on Indium Oxide Nanowire Transistors using Femtosecond Laser
Kim, Seongmin,Kim, Sunkook,Srisungsitthisunti, Pornsak,Lee, Chunghun,Xu, Min,Ye, Peide D.,Qi, Minghao,Xu, Xianfan,Zhou, Chongwu,Ju, Sanghyun,Janes, David B. American Chemical Society 2011 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.115 No.34
<P>Nanowire materials have gained great interest as promising candidates for high-performance logic devices to sustain the progress in device scaling. However, little research has been conducted to investigate the role of contacts on the device performance accompanied by an appropriate physical model in nanodevices, although effects of the contacts will prevail as the channel scales. In this study, we investigate the effect of annealing using a femtosecond-laser focused at the contact region between the source-drain electrodes and the nanowire. On the basis of the direct comparison of device characteristics before and after annealing, a contact model is introduced, which could be generally applicable to nanowire transistors with overlap between gate region and source-drain regions. Low-frequency noise measurements in the devices reveal that the <I>I</I><SUB>d</SUB><SUP>2</SUP> normalized noise spectrum and Hooge’s constant are reduced following laser annealing.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-34/jp203342j/production/images/medium/jp-2011-03342j_0004.gif'></P>