Yonsei Institute of Convergence Technology

Incheon, South Korea

Yonsei Institute of Convergence Technology

Incheon, South Korea
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Kim H.-J.,Yonsei University | Kim H.-J.,Yonsei Institute of Convergence Technology | Yang S.,Yonsei University | Yang S.,Yonsei Institute of Convergence Technology | And 8 more authors.
Nano Research | Year: 2017

Electrical and optical enhancements of single-layer semiconducting materials such as transition metal dichalcogenides have recently been studied to achieve sensitive properties via external treatments, such as the formation of organic/inorganic protecting layers on field-effect transistors (FETs), thermal annealing, and nano-dot doping of sensors and detectors. Here, we propose a new analytical approach to electrical and optical enhancement through a passivation process using atomic layer deposition (ALD), and demonstrate a synthesized MoS2 monolayer incorporated with Al atoms in an Al2O3 passivation layer. The incorporated Al atoms in the MoS2 monolayer are clearly observed by spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) and TEM-energy-dispersive X-ray spectroscopy results. We demonstrate that the chemically incorporated FETs exhibit highly enhanced mobilities of approximately 3.7 cm2·V−1·s−1, forty times greater than that of as-synthesized MoS2, with a three-fold improvement in the photoluminescence properties. [Figure not available: see fulltext.] © 2017 Tsinghua University Press and Springer-Verlag GmbH Germany


Moon J.Y.,Yonsei Institute of Convergence Technology | Lee H.S.,Kyungpook National University
Electronic Materials Letters | Year: 2017

We fabricated solution-processed thin film transistors (TFTs) with In-doped Mg0.2Zn0.8O channel layers and investigated the effect of In doping on the device performance. With increasing In content in the Mg0.2Zn0.8O films, the off-current decreased and the threshold voltage shifted in the positive direction. This was due to the reduction in carrier concentration caused by In addition. Disordered atomic arrangements such as stacking faults were observed with increasing In content in the Mg0.2Zn0.8O thin films. Such structural defects could generate localized acceptor states, leading to a reduction in carrier concentration. These results suggest that In doping can be a useful technique to produce more reliable solution-processed Mg0.2Zn0.8O materials for TFTs and other applications. [Figure not available: see fulltext.] © 2017, The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.


Cho A.-J.,Yonsei University | Cho A.-J.,Yonsei Institute of Convergence Technology | Park K.,Yonsei Institute of Convergence Technology | Park S.,Yonsei University | And 6 more authors.
Journal of Materials Chemistry C | Year: 2017

Two-dimensional (2D) materials are known for their unique properties and potential for application in various electronic and optoelectronic devices. Since 2D semiconductors have weak bonding between the layers, they can be easily separated into several nanometer-thick layers which still maintain their characteristics. GaTe is a p-type 2D semiconductor having a direct bandgap. By combining multi-layer GaTe and thin-film IGZO, we have fabricated a p-n heterojunction, a fundamental unit of optoelectronic devices. In this paper, we propose the first fully transparent solar cell using a 2D material, based on a GaTe/IGZO heterostructure. The device shows a high transparency of ∼90% and an efficiency of 0.73% with a fill factor of 37%. It exhibits instantaneous generation of photo-carriers under periodic light pulses. Further analysis of the operating mechanism was conducted by studying its band alignments. The transparency of our GaTe/IGZO solar cell can overcome its relatively low efficiency, as it can be installed in a much larger scale and the total amount of generated power will surpass that of the conventional solar cell. Furthermore, advances in the large-scale growth of GaTe will enhance the power conversion efficiency, and finally enable the adoption of 2D active layer based highly transparent, thin-film solar cells for building integrated photovoltaic systems. © 2017 The Royal Society of Chemistry.


PubMed | Yonsei Institute of Convergence Technology and University of California at Davis
Type: Journal Article | Journal: Developmental psychology | Year: 2016

Four experiments examined how faces compete with physically salient stimuli for the control of attention in 4-, 6-, and 8-month-old infants (N = 117 total). Three computational models were used to quantify physical salience. We presented infants with visual search arrays containing a face and familiar object(s), such as shoes and flowers. Six- and 8-month-old infants looked first and longest at faces; their looking was not strongly influenced by physical salience. In contrast, 4-month-old infants showed a visual preference for the face only when the arrays contained 2 items and the competitor was relatively low in salience. When the arrays contained many items or the only competitor was relatively high in salience, 4-month-old infants looks were more often directed at the most salient item. Thus, over ages of 4 to 8 months, physical salience has a decreasing influence and faces have an increasing influence on where and how long infants look.


Cho A.-J.,Yonsei University | Cho A.-J.,Yonsei Institute of Convergence Technology | Park K.C.,Konkuk University | Kwon J.-Y.,Yonsei University | Kwon J.-Y.,Yonsei Institute of Convergence Technology
Nanoscale Research Letters | Year: 2015

For several years, graphene has been the focus of much attention due to its peculiar characteristics, and it is now considered to be a representative 2-dimensional (2D) material. Even though many research groups have studied on the graphene, its intrinsic nature of a zero band-gap, limits its use in practical applications, particularly in logic circuits. Recently, transition metal dichalcogenides (TMDs), which are another type of 2D material, have drawn attention due to the advantage of having a sizable band-gap and a high mobility. Here, we report on the design of a complementary inverter, one of the most basic logic elements, which is based on a MoS2 n-type transistor and a WSe2 p-type transistor. The advantages provided by the complementary metal-oxide-semiconductor (CMOS) configuration and the high-performance TMD channels allow us to fabricate a TMD complementary inverter that has a high-gain of 13.7. This work demonstrates the operation of the MoS2 n-FET and WSe2 p-FET on the same substrate, and the electrical performance of the CMOS inverter, which is based on a different driving current, is also measured. © 2015, Cho et al.; licensee Springer.


Yoon S.,Yonsei Institute of Convergence Technology | Bang J.,Yonsei Institute of Convergence Technology | Song Y.,Yonsei Institute of Convergence Technology | Oh J.,Yonsei University
Thin Solid Films | Year: 2015

A complementary metal-oxide semiconductor (CMOS)-compatible Au-free Si/Ti/Al/Cu ohmic metallization scheme has been developed for AlGaN/GaN power transistors epitaxially grown on Si substrates. The Si/Ti/Al/Cu metallization exhibited a low specific contact resistance of 3.5 × 10- 6 ω cm2 after optimizing the Si interface layer. The ohmic metal surface was smooth with a root-mean-square roughness of 24 nm. Physical characterization confirmed that Cu diffusion into the semiconductor was suppressed because locally segregated TiSix alloys acted as a barrier. Shallow interfacial reactions of localized TiN alloys occurred in the AlGaN/GaN heterostructure. Without a designated diffusion barrier as in conventional Au-based metallization, the contact resistivity and surface morphology in Si/Ti/Al/Cu improved significantly, which helps address critical challenges associated with the fabrication of AlGaN/GaN power transistors on a Si CMOS platform. © 2015 Elsevier B.V.


Jung S.-M.,Yonsei University | Won Y.-Y.,Yonsei Institute of Convergence Technology | Han S.-K.,Yonsei University
International Conference on ICT Convergence | Year: 2013

We propose a technique to reduce the OBI noise in OFDMA-PON link. A self-homodyne balanced detection can improve the SNR of DMT signal as well as reduce OBI noise with the help of local laser. © 2013 IEEE.


Lee S.,Yonsei University | Ju D.Y.,Yonsei Institute of Convergence Technology
IEEE ISI 2013 - 2013 IEEE International Conference on Intelligence and Security Informatics: Big Data, Emergent Threats, and Decision-Making in Security Informatics | Year: 2013

Smartphone OS, such as Android, enables us to install third party applications. However, security threats of malicious applications are rapidly increasing due to the nature of the third party applications where only developers can assign required permissions. For this reason, attackers can inject exploits into a normal application with inappropriately acquired permissions. In this paper, we propose a method to distinguish an application by analyzing permissions set and enhanced user interfaces to improve the chance of making right decisions. The proposed methods are intended for users to make better decisions with more information provided by the system. © 2013 IEEE.


Namgung S.D.,Yonsei University | Namgung S.D.,Yonsei Institute of Convergence Technology | Yang S.,Yonsei University | Yang S.,Yonsei Institute of Convergence Technology | And 7 more authors.
Nanoscale Research Letters | Year: 2015

Two-dimensional materials have recently been spotlighted, due to their unique properties in comparison with conventional bulk and thin-film materials. Among those materials, MoS2 is one of the promising candidates for the active layer of electronic devices because it shows high electron mobility and pristine band gap. In this paper, we focus on the evolution of the electrical property of the MoS2 field-effect transistor (FET) as a function of post-annealing temperature. The results indicate that the off current drastically decreased at 200°C and increased at 400°C while other factors, such as the mobility and threshold voltage, show little variation. We consider that the decreasing off current comes from the rearrangement of the MoS2 film and the elimination of the surface residue. Then, the increasing off current was caused by the change of the material's composition and adsorption of H2O and O2. © 2015, Namgung et al.; licensee Springer.


PubMed | Yonsei University and Yonsei Institute of Convergence Technology
Type: | Journal: Nanoscale research letters | Year: 2015

Two-dimensional materials have recently been spotlighted, due to their unique properties in comparison with conventional bulk and thin-film materials. Among those materials, MoS2 is one of the promising candidates for the active layer of electronic devices because it shows high electron mobility and pristine band gap. In this paper, we focus on the evolution of the electrical property of the MoS2 field-effect transistor (FET) as a function of post-annealing temperature. The results indicate that the off current drastically decreased at 200C and increased at 400C while other factors, such as the mobility and threshold voltage, show little variation. We consider that the decreasing off current comes from the rearrangement of the MoS2 film and the elimination of the surface residue. Then, the increasing off current was caused by the change of the materials composition and adsorption of H2O and O2.

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