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Structural characterization of Eu-doped GaN by transmission electron microscopy
Jongwon Seo,Shaoqiang Chen,Junji Sawahata,Masaharu Mitome,Katsuhiro Akimoto 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.1
The structural properties of Eu-doped GaN films grown on sapphire (0001) substrates by molecular beam epitaxy were studied using cross sectional transmission electron microscopy (TEM). The Eu concentration was estimated to be about 2at.% by Rutherford backscattering spectrometry and energy dispersive X-ray spectroscopy. Selected area diffraction patterns of the film showed a hexagonal structure, and no other anomalous patterns such as from Eu and EuN were observed. The high resolution TEM observation of the films showed a high density of stacking faults which was hardly observed in undoped GaN, bending layers and a small portion of cubic phase. The causes of the formation of stacking faults and bending of layers are discussed. The structural properties of Eu-doped GaN films grown on sapphire (0001) substrates by molecular beam epitaxy were studied using cross sectional transmission electron microscopy (TEM). The Eu concentration was estimated to be about 2at.% by Rutherford backscattering spectrometry and energy dispersive X-ray spectroscopy. Selected area diffraction patterns of the film showed a hexagonal structure, and no other anomalous patterns such as from Eu and EuN were observed. The high resolution TEM observation of the films showed a high density of stacking faults which was hardly observed in undoped GaN, bending layers and a small portion of cubic phase. The causes of the formation of stacking faults and bending of layers are discussed.
[디젤엔진부문] Offset-대향 분출염에 의한 NOx 저감
서종원(Seo Jongwon),이창진(Lee Changjin) 한국자동차공학회 1999 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1999 No.11_1
The NOx emissions and combustion characteristics are experimentally compared with an offset with the previous results obtained with counter-orifice configuration. The offset-opposed impinging flame creates stronger vortex around the stagnation point than the opposed flame. The strong vortex creates a uniform field of isotropic turbulence through a cascade of turbulent kinetic energy transfer and provides more turbulent kinetic energy to turbulent eddies resulting in the delay of turbulence dissipation. The principal objective of this study is to develop the low NOx combustor by distributed reaction flame. It was found that the offset-opposed impinging flame decreased more NOx and improved the combustion efficiency than the opposed flame
A 90-nm CMOS 144 GHz Injection Locked Frequency Divider with Inductive Feedback
Hyogi Seo,Seungwoo Seo,Jongwon Yun,Jae-Sung Rieh 대한전자공학회 2011 Journal of semiconductor technology and science Vol.11 No.3
This paper presents a 144 GHz divide-by-2 injection locked frequency divider (ILFD) with inductive feedback developed in a commercial 90-nm Si RFCMOS technology. It was demonstrated that division-by-2 operation is achieved with input power down to -12 dBm, with measured locking range of 0.96 GHz (144.18 - 145.14 GHz) at input power of -3 dBm. To the authors" best knowledge, this is the highest operation frequency for ILFD based on a 90nm CMOS technology. From supply voltage of 1.8 V, the circuit draws 5.7 mA including both core and buffer. The fabricated chip occupies 0.54 mm x 0.69 mm including the DC and RF pads.
Wavelet Transform을 이용한 flow-chart 인식
서정주,박종원,류재철 충남대학교 기초과학연구소 1997 忠南科學硏究誌 Vol.24 No.1
This paper studies the algorithm that recognizes a flow-chart. The algorithm recognizes the shapes, the sizes, and the locations of the figures in a flow-chart, and then makes a program as a result by using the wavelet transform for speed up.
Electrochemical Determination of As(III) at Nanoporous Gold Electrodes with Controlled Surface Area
Seo, Min Ji,Kastro, Kanido Camerun,Kim, Jongwon Korean Chemical Society 2019 대한화학회지 Vol.63 No.1
Because arsenic (As) is a chemical substance toxic to humans, there have been extensive investigations on the development of As detection methods. In this study, the electrochemical determination of As on nanoporous gold (NPG) electrodes was investigated using anodic stripping voltammetry. The electrochemical surface area of the NPG electrodes was controlled by changing the reaction times during the anodization of Au for NPG preparation, and its effect on the electrochemical behavior during As detection was examined. The detection efficiency of the NPG electrodes improved as the roughness factor of the NPG electrodes increased up to around 100. A further increase in the surface area of the NPG electrodes resulted in a decrease of the detection efficiency due to high background current levels. The most efficient As detection efficiency was obtained on the NPG electrodes prepared with an anodization time of 50 s. The effects of the detection parameters and of the Cu interference in As detection were investigated and the NPG electrode was compared to flat Au electrodes.
Seo, Bora,Choi, Suhee,Kim, Jongwon American Chemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.2
<P>Nanostructured Au surfaces have unique and attractive properties as functional materials in many fields such as heterogeneous catalysis and electrocatalysis. Electrochemical deposition of Au has received much attention as a simple route for the fabrication of Au surface nanostructures. In this study, we report a simple electrodeposition of Au nanoplate structures from Au(CN)<SUB>2</SUB><SUP>−</SUP> on Au surfaces in the absence of additives or premodification of electrode surfaces. The shape of the Au nanoplates as well as their surface structures is unique compared to other Au nanostructures electrodeposited from commonly employed AuCl<SUB>4</SUB><SUP>−</SUP> complexes. The nanoplate Au surfaces exhibit unique electrocatalytic activities for oxygen reduction and glucose oxidation, which originate from the Au(110) and Au(100) facets present on nanoplate surfaces. A simple preparation of well-defined Au nanoplate structures would allow new opportunities in various areas utilizing Au-based substrates through further modification of Au surfaces.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2011/aamick.2011.3.issue-2/am101018g/production/images/medium/am-2010-01018g_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am101018g'>ACS Electronic Supporting Info</A></P>