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Jang, Seunghun,Im, Jino,Choi, Min,Lee, Jeong-O.,Kong, Ki-jeong,Chang, Hyunju Elsevier 2017 Carbon Vol.119 No.-
<P>The electronic density of states (DOS) in carbon nanotubes (CNTs) was recently measured using a structure comprising a single CNT-based field effect transistor (FET) device with an indium (In) electrode. Here, we report the bonding characteristics and electronic structure of the contact interface between Group 13 metals (In, Ga, Al) and (8,0) semiconducting CNTs using first-principles density functional theory (DFT) calculations. Our calculation results showed that CNTs in contact with Al, Ga, or In surfaces display lower binding energies to their contact metal surfaces than that of Pd surface while also preserving their original electronic properties. These results originate from the absence of d-orbitals in the Group 13 metals near the Fermi level, the large equilibrium distance, and the deficiencies in electron charge density at the metal surfaces. This study deepens our understanding of the contact properties between Group 13 metals and CNTs. (C) 2017 Elsevier Ltd. All rights reserved.</P>
Minimum MSE Design for Multiuser MIMO Relay
Seunghun Jang,Janghoon Yang,Dong Ku Kim IEEE 2010 IEEE communications letters Vol.14 No.9
<P>We study a joint optimal design of transceiver and relaying architecture in terms of mean square error (MSE) performance for multi-user multiple-input multiple-output (MIMO) relaying system. We show a duality relationship in the design of MSE-optimal transceiver and relaying architecture. Based on that, we devise an alternating algorithm, which converges and provides a suboptimal joint design of transceiver and relaying. By simulation, we show that the proposed joint design improves on the average MSE performance of the existing transceiver and relaying architectures.</P>
Jang, Seunghun,Joo, Beom Soo,Kim, Sung,Kong, Ki-jeong,Chang, Hyunju,Yu, Byung Deok,Han, Moonsup The Royal Society of Chemistry 2015 Journal of Materials Chemistry C Vol.3 No.33
<▼1><P>The investigation of photoluminescence and first-principles calculations clarifies the relationship between the hydrogen passivation of N at the interface and the observed band gap reduction of the embedded Si nanocrystal (NC) for Si NC/SiO2 multilayers containing interfacial nitrogens after proton irradiation.</P></▼1><▼2><P>Si nanocrystal (NC)/SiO2 multilayers containing interfacial nitrogens are formed by radiofrequency magnetron-sputtering and post-annealing. By analyzing the photoluminescence (PL) of the multilayer structures after proton irradiation (PI), we found that the peak at ∼740 nm was shifted toward shorter wavelengths and that its intensity was considerably suppressed. Furthermore, a new peak simultaneously appeared at ∼500 nm. We interpret that PI not only modifies the shapes of the Si NCs and generate defects at the NC/SiO2 interface, but also induces simultaneously hydrogen passivation (HP) of interfacial nitrogens due to the attenuated protons. To investigate the relationship between the HP of N at the Si NC/SiO2 interface and the observed band gap reduction of Si NC structures within the SiO2 matrix, we modeled the atomic configurations at the interface and applied first-principles calculations. The results clearly indicate that the HP of composite structures containing Si–N bonds at the Si NC/SiO2 interface induces the blue-shift in PL. We expect that this investigation helps to pave the way for developing more efficient Si-based light emitting devices or solar cells.</P></▼2>
MSE Duality for Multi-User MIMO Relay System
Seunghun Jang,Young-Min Cho,Janghoon Yang,Dong Ku Kim IEEE 2012 IEEE communications letters Vol.16 No.11
<P>This paper shows how uplink (UL)-downlink (DL) mean square error (MSE) duality holds in a single relay aided multi-user multiple-input multiple-output (MU-MIMO) system. Specifically, it is shown that the MSE duality holds for three levels of MSE which are sum-MSE (SMSE), per user MSE, and per stream MSE. For each case of duality level, we consider both total power constraint and separate power constraint. We also provide a conversion method which transforms a given transceiver and scale factor in DL to equivalent ones in UL for each case of duality level and each case of power constraint.</P>