SUNGKYUNKWAN UNIVERSITY (SKKU), SEOUL, KOREA


November-January, 2017 Vol. 1
Worldwide
  • SKKU-AACHEN Univ. Establish 'Korea-German Int'l Research Center'
  • 2nd SKKU-HUST Bilateral Graduate Student Workshop Successfully Finished
  • 2016 SKKU-GUGC Joint Workshop for Furthering Scientific Collaboration
  • SKKU Holds 3rd Central & Eastern Europe Korean Writing Contest in Vienna
Discovery
  • SKKU Reaches Top Level in Korea for Main Research Businesses in 2016
  • SKKU Receives 'S grade' for Research Fund Administration System
  • SKKU Ranked No.3 University in Korea by US News & World Report
Top Schools
  • SKKU Univ. for Creative Korea Held the 'Sungkyun C-School Intensive Program'
  • Special Lecture from Chair of the National Endowment for the Humanities (NEH)
  • French Law Book Collection Donated From Emeritus Prof. Yamaguchi
Leading Alumni in a Global Society
  • New Year's Message from SKKU President Kyu Sang Chung
Leading Alumni in a Global Society
  • Noticeable Articles Recently Published in Journals
Leading Alumni in a Global Society
  • SKKU Receives 'Best Group Work Award' at IETF Hackathon
  • 2016 Graduate School of China '一帶一路' Long March
  • Students from SKKU Receive 2nd Prize at BIOMOD Competition
  • SKKU Students Win at CFA Institute Research Challenge 2016
Lithium-ion Battery with 5x Capacity Developed

Perovskite solar cells, which are receiving a great deal of attention due to their low cost and high efficiency, are regarded as a promising photovoltaic technology.

Perovskite solar cells are easily produced by solution-process but perovskite's thin films are polycrystalline, and grain boundaries that form are thought to be responsible for causing recombination and the trapping of charge carriers.

The research team led by Prof. Nam-Gyu PARK successfully demonstrated the production of highly efficient and reproducible perovskite solar cells through a grain boundary healing process resulting in a power conversion efficiency of 20.4%.

The team invented the world's first long-term stable perovskite solar cells and their work was published in the journal Nature Scientific Report August 2012. This research has been cited more than 1,260 times since 2012, and gained recognition for its excellence.

The Instant a Water Drop Evaporates Has Been Captured

In collaboration with Sungkyunkwan University, researchers from the Center for Integrated Nanostructure Physics within the Institute for Basic Science (IBS) have devised a new memory device inspired by the neuron connections of the human brain. The research, published in Nature Communications, highlights the devise's highly reliable performance, long retention time, and endurance. Moreover, its stretchability and flexibility makes it a promising tool for next-generation soft electronics attached to clothes or the body.

The brain is able to learn and memorize thanks to a huge number of connections between neurons. The information you memorize is transmitted through synapses from one neuron to the next as an electro-chemical signal. Inspired by these connections, IBS scientists constructed a memory called two-terminal tunneling random access memory (TRAM), where two electrodes referred to as drain and source, resemble the two communicating neurons of the synapse. While mainstream mobile electronics like digital cameras and mobile phones use the so-called three-terminal flash memory, the advantage of two-terminal memories like TRAM is that two-terminal memories do not need a thick and rigid oxide layer. "Flash memory is still more reliable and has better performance, but TRAM is more flexible and can be scalable," explains Professor Yu.

TRAM is made up of a stack of one-atom-thick, or a few atom-thick 2D crystal layers: one layer of the semiconductor molybdenum disulfide (MoS2) with two electrodes (drain and source), an insulating layer of hexagonal boron nitride (h-BN) and a graphene layer. In simple terms, memory is created (logical-0), read and erased (logical-1) by the flowing of charges through these layers. TRAM stores data by keeping electrons on its graphene layer. By applying different voltages between the electrodes, electrons flow from the drain to the graphene layer, tunneling through the insulating h-BN layer. The graphene layer becomes negatively charged and memory is written and stored and vice versa. When positive charges are introduced in the graphene layer, memory is erased.

Find more information at:
http://www.nature.com/articles/ncomms12725

Restraining Fat Stem Cell Differentiation to Avoid Child Obesity

A research team led by Prof. Young Hee LEE from the Institute for Basic Science successfully analyzed the atomic structure and electrical characteristics of MoS2 which are labeled as new materials for the next generation, along with Graphene.

Grain boundaries in monolayer transition metal dichalcogenides have unique atomic defect structures and band dispersion relations that depend on the inter-domain misorientation angle. They explore misorientation angle-dependent electrical transport at grain boundaries in monolayer MoS2 by correlating the atomic defect structures of measured devices analyzed with transmission electron microscopy, and first-principles calculations. Transmission electron microscopy indicates that grain boundaries are primarily composed of 5-7 dislocation cores with periodicity and additional complex defects formed at high angles, obeying the classical low-angle theory for angles <22°. The inter-domain mobility is minimized for angles <9° and increases nonlinearly by two orders of magnitude before saturating at ~16cm2 V-1 s-1 around misorientation angle≈20°. This trend is explained via grain-boundary electrostatic barriers estimated from density functional calculations and experimental tunnelling barrier heights, which are ≈0.5 eV at low angles and ≈0.15 eV at high angles (≥20°).

The results provide practical expectations regarding transport properties in large-area films, which are restricted largely by the poor mobility across LA GBs. The results obtained in this work are applicable to other similar 2D systems, and contribute to the fundamental understanding of transport in semiconductors.

This work was published at Nature Communications magazine which is affiliated with Nature.

Finding New Protein to Cure Obesity and Metabolic Diseases

A research team at the Department of Chemistry (Prof. Ji Man Kim) successfully demonstrated a durable nanostructure of ordered mesoporous Tin (Sn)-based intermetallic materials, enabling control of the volume changes during the charge-discharge process. Li-ion batteries (LIBs) are a key-enabling technology for addressing the power and energy demands of electric vehicles and stationary electrical storage for renewable energy, as well as mobile electronics. However, the energy density of currently commercialized LIBs is already close to its technological limit. In order to achieve the battery performances that all applications expect, much effort has been made to develop new electrode materials to improve both the energy density and cycle performance of LIBs. The main goal of this research is to enable energy densities that are higher than the theoretical limit predicted for current lithium ion intercalation batteries.

Tin (Sn) has been considered as an attractive anode material for Li-ion batteries (LIBs) due to the appropriate working potential (average 0.5 V vs. Li/Li+) and high theoretical capacity (993 mAh g-1). However, structural deterioration originated from severe volume variation during the lithiation–delithiation process is one of the most well-known drawbacks, which causes a failure of cycle stability.

The research team developed the preparation and electrochemical behaviors of highly ordered mesoporous CoSn intermetallic anodes which represent superior electrochemical performance, by combining the advantages of intermetallic framework and nanoporous structure.

Furthermore, they unveiled the nanostructural changes during the battery operation by in operando SAXS investigation, so that they can provide more details on volume changes of the electrode materials during cycling. Most promising is that the presence of Co as an electrochemically inactive buffer element in the mesoporous intermetallic materials leads to the durable nanostructure upon prolonged cycling. These findings should give valuable guidance for designing innovative nanostructured material.

The full details of the research were published in the scientific journal Advanced Functional Materials under the subject name "Discovering Dual-Buffer Effects on Lithium Storage: Durable Nanostructure of Ordered Mesoporous Co-Sn Intermetallic Electrode".

Find more information at:
http://onlinelibrary.wiley.com/doi/10.1002/adfm.201600121/full

‘The World Class High-Performance Photodetector’ Has Finally Been Created

A joint research team led by Prof. Il Min KWON of SKKU School of Medicine and Prof. Steven L. Mcknight of the University of Texas Southwestern Medical Center, discovered the intercellular targets of toxic PR Poly-dipeptides encoded by C9orf72 repeat expansion which is frequently found in Amyotrophic Lateral Sclerosis (ALS) (also known as Lou Gehrig's disease). The result of the study may offer a unified means of considering mechanisms of pathogenicity for a broad spectrum of neurodegenerative diseases.

ALS is a specific disease that causes the death of motor neurons which control voluntary muscles. ALS is characterized by stiff muscles, muscle twitching, and gradually worsening weakness due to muscles decreasing in size which results in difficulty speaking, swallowing, and eventually breathing. According to the ALS Association, approximately 350,000 patients (2500 in Korea) are suffering from the disease and about 100,000 people die per year. Although there is not yet a cure or treatment that halts or reverses ALS, scientists have made significant progress in learning more about this disease. Several research projects which were revealed to the public in 2011 have proved that the variation of cell C9orf72 is the main reason for ALS disease occurring.

In this research, two complementary approaches were used in search of the intracellular targets of the toxic PR poly-dipeptide, encoded by the repeat sequences expanded in the C9orf72 form of amyotrophic lateral sclerosis. The top categories of PRn-bound proteins include constituents of non-membrane invested cellular organelles and intermediate filaments. PRn targets are enriched for the inclusion of low complexity (LC) sequences. Evidence is presented indicating that LC sequences represent the direct target of PRn binding and that interaction between the PRn poly-dipeptide and LC domains is polymer dependent. These studies indicate that PRn-mediated toxicity may result from broad impediments to the dynamics of cell structure and information flow from gene, to message, to protein.

A Conductive Nano-Bio Composite 'Fullerene-Protein' Structure in a Regular Arrangement

An SKKU research team led by Prof. Jin Hong PARK successfully developed technology for negative differential resistance devices and demonstrated a ternary inverter as a multi-valued logic application.

Recently, negative differential resistance devices have attracted considerable attention due to their folded current–voltage characteristic which presents multiple threshold voltage values. Because of this remarkable property, studies associated with negative differential resistance devices have been explored for realizing multi-valued logic applications. The research team at SKKU demonstrated a negative differential resistance device based on a phosphorene/rhenium disulfide (BP/ReS2) heterojunction that is formed by type-III broken-gap band alignment, showing high peak-to-valley current ratio values of 4.2 and 6.9 at room temperature, and 180 K respectively.

Also, the carrier transport mechanism of the BP/ReS2 negative differential resistance device was investigated in detail by analyzing the tunneling and diffusion currents at various temperatures with the proposed analytic negative differential resistance device model. Furthermore, they demonstrated a ternary inverter as a multi-valued logic application. This study of a two-dimensional material heterojunction is a step forward towards future multi-valued logic device research.

The result of the study was published in Nature Communication on Nov 7th with a thesis titled: Phosphorene/Rhenium Disulfide Heterojunction-based Negative Differential Resistance Device for Multi-Valued Logic.

Find more information at:
http://www.nature.com/articles/ncomms13413


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