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Making Graphene Using Laser-induced Phase Separation
IBS & KAIST researchers clarify how laser annealing technology can lead to the production of ultrathin nanomaterials All our smart phones have shiny flat AMOLED (active-matrix organic light-emitting diode) displays. Behind each single pixel of these displays hides at least two silicon transistors which are mass-manufactured using laser annealing technology. While the traditional methods to make the transistors use temperature above 1,000°C, the laser technique reaches the same results at low temperatures even on plastic substrates (melting temperature below 300°C). Interestingly, a similar procedure can be used to generate crystals of graphene. Graphene is a strong and thin nano-material made of carbon, its electric and heat-conductive properties have attracted the attention of scientists worldwide. Professor Keon Jae Lee of the Materials Science and Engineering Department at KAIST and his research group at the Center for Multidimensional Carbon Materials within the Institute for Basic Science (IBS), as well as Professor Sung-Yool Choi of the Electrical Engineering School at KAIST and his research team discovered graphene synthesis mechanism using laser-induced solid-state phase separation of single-crystal silicon carbide (SiC). This study, available in Nature Communications, clarifies how this laser technology can separate a complex compound (SiC) into its ultrathin elements of carbon and silicon. Although several fundamental studies presented the effect of excimer lasers in transforming elemental materials like silicon, the laser interaction with more complex compounds like SiC has rarely been studied due to the complexity of compound phase transition and ultra-short processing time. With high resolution microscope images and molecular dynamic simulations, scientists found that a single-pulse irradiation of xenon chloride excimer laser of 30 nanoseconds melts SiC, leading to the separation of a liquid SiC layer, a disordered carbon layer with graphitic domains (about 2.5 nm thick) on top surface and a polycrystalline silicon layer (about 5 nm) below carbon layer. Giving additional pulses causes the sublimation of the separated silicon, while the disordered carbon layer is transformed into a multilayer graphene. "This research shows that the laser material interaction technology can be a powerful tool for the next generation of two dimensional nanomaterials," said Professor Lee. Professor Choi added: "Using laser-induced phase separation of complex compounds, new types of two dimensional materials can be synthesized in the future." High-resolution transmission electron microscopy shows that after just one laser pulse of 30 nanoseconds, the silicon carbide (SiC) substrate is melted and separates into a carbon and a silicon layer. More pulses cause the carbon layer to organize into graphene and the silicon to leave as gas. Molecular dynamics simulates the graphene formation mechanism. The carbon layer on the top forms because the laser-induced liquid SiC (SiC (l)) is unstable. (Press Release by Courtesy of the Institute for Basic Science (IBS))
Graphene-Based Transparent Electrodes for Highly Efficient Flexible OLEDs
A Korean research team developed an ideal electrode structure composed of graphene and layers of titanium dioxide and conducting polymers, resulting in highly flexible and efficient OLEDs. The arrival of a thin and lightweight computer that even rolls up like a piece of paper will not be in the far distant future. Flexible organic light-emitting diodes (OLEDs), built upon a plastic substrate, have received greater attention lately for their use in next-generation displays that can be bent or rolled while still operating. A Korean research team led by Professor Seunghyup Yoo from the School of Electrical Engineering, KAIST and Professor Tae-Woo Lee from the Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH) has developed highly flexible OLEDs with excellent efficiency by using graphene as a transparent electrode (TE) which is placed in between titanium dioxide (TiO2) and conducting polymer layers. The research results were published online on June 2, 2016 in Nature Communications. OLEDs are stacked in several ultra-thin layers on glass, foil, or plastic substrates, in which multi-layers of organic compounds are sandwiched between two electrodes (cathode and anode). When voltage is applied across the electrodes, electrons from the cathode and holes (positive charges) from the anode draw toward each other and meet in the emissive layer. OLEDs emit light as an electron recombines with a positive hole, releasing energy in the form of a photon. One of the electrodes in OLEDs is usually transparent, and depending on which electrode is transparent, OLEDs can either emit from the top or bottom. In conventional bottom-emission OLEDs, an anode is transparent in order for the emitted photons to exit the device through its substrate. Indium-tin-oxide (ITO) is commonly used as a transparent anode because of its high transparency, low sheet resistance, and well-established manufacturing process. However, ITO can potentially be expensive, and moreover, is brittle, being susceptible to bending-induced formation of cracks. Graphene, a two-dimensional thin layer of carbon atoms tightly bonded together in a hexagonal honeycomb lattice, has recently emerged as an alternative to ITO. With outstanding electrical, physical, and chemical properties, its atomic thinness leading to a high degree of flexibility and transparency makes it an ideal candidate for TEs. Nonetheless, the efficiency of graphene-based OLEDs reported to date has been, at best, about the same level of ITO-based OLEDs. As a solution, the Korean research team, which further includes Professors Sung-Yool Choi (Electrical Engineering) and Taek-Soo Kim (Mechanical Engineering) of KAIST and their students, proposed a new device architecture that can maximize the efficiency of graphene-based OLEDs. They fabricated a transparent anode in a composite structure in which a TiO2 layer with a high refractive index (high-n) and a hole-injection layer (HIL) of conducting polymers with a low refractive index (low-n) sandwich graphene electrodes. This is an optical design that induces a synergistic collaboration between the high-n and low-n layers to increase the effective reflectance of TEs. As a result, the enhancement of the optical cavity resonance is maximized. The optical cavity resonance is related to the improvement of efficiency and color gamut in OLEDs. At the same time, the loss from surface plasmon polariton (SPP), a major cause for weak photon emissions in OLEDs, is also reduced due to the presence of the low-n conducting polymers. Under this approach, graphene-based OLEDs exhibit 40.8% of ultrahigh external quantum efficiency (EQE) and 160.3 lm/W of power efficiency, which is unprecedented in those using graphene as a TE. Furthermore, these devices remain intact and operate well even after 1,000 bending cycles at a radius of curvature as small as 2.3 mm. This is a remarkable result for OLEDs containing oxide layers such as TiO2 because oxides are typically brittle and prone to bending-induced fractures even at a relatively low strain. The research team discovered that TiO2 has a crack-deflection toughening mechanism that tends to prevent bending-induced cracks from being formed easily. Professor Yoo said, “What’s unique and advanced about this technology, compared with previous graphene-based OLEDs, is the synergistic collaboration of high- and low-index layers that enables optical management of both resonance effect and SPP loss, leading to significant enhancement in efficiency, all with little compromise in flexibility.” He added, “Our work was the achievement of collaborative research, transcending the boundaries of different fields, through which we have often found meaningful breakthroughs.” Professor Lee said, “We expect that our technology will pave the way to develop an OLED light source for highly flexible and wearable displays, or flexible sensors that can be attached to the human body for health monitoring, for instance.” The research paper is entitled “Synergistic Electrode Architecture for Efficient Graphene-based Flexible Organic Light-emitting Diodes” (DOI. 10.1038/NCOMMS11791). The lead authors are Jae-Ho Lee, a Ph.D. candidate at KAIST; Tae-Hee Han, a Ph.D. researcher at POSTECH; and Min-Ho Park, a Ph.D. candidate at POSTECH. This study was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF) through the Center for Advanced Flexible Display (CAFDC) funded by the Ministry of Science, ICT and Future Planning (MSIP); by the Center for Advanced Soft-Electronics funded by the MSIP as a Global Frontier Project; by the Graphene Research Center Program of KAIST; and by grants from the IT R&D Program of the Ministry of Trade, Industry and Energy of Korea (MOTIE). Figure 1: Application of Graphene-based OLEDs This picture shows an OLED with the composite structure of TiO2/graphene/conducting polymer electrode in operation. The OLED exhibits 40.8% of ultrahigh external quantum efficiency (EQE) and 160.3 lm/W of power efficiency. The device prepared on a plastic substrate shown in the right remains intact and operates well even after 1,000 bending cycles at a radius of curvature as small as 2.3 mm. Figure 2: Schematic Device Structure of Graphene-based OLEDs This picture shows the new architecture to develop highly flexible OLEDs with excellent efficiency by using graphene as a transparent electrode (TE).
KAIST Holds Its Fourth Public Art Exhibition
KAIST hosted an opening ceremony for the annual art exhibition on December 3, 2015 at the KAIST Institute building. The KAIST Art and Design Committee first organized the event in 2012 to promote the integration of art and technology. This year’s event entitled “Understanding the Purpose of an Object” will display 20 art pieces under six themes. Artist Keumhong Lee, Haeyool Roh, Joon Kim, Kyung Lee, and Juhae Yang participated in the exhibition. The names of some of the art pieces include “Feedback Field” by Joon Kim, “Self Action” by Haeyool Roh, and “Net of Time” by Juhae Yang. Juhae Yang believes that, in the digital age, an identity of an object is defined by the traces of light which we read in the information hidden in the barcodes. Based on this interpretation, she transforms the black bars and white spaces into a harmony of colors and sounds. The continuum of colors and sounds in her work arouses time-space synesthesia. Professor Sangmin Bae of the Industrial Design Department, the Director of the KAIST Art and Design Committee, hopes that the exhibition will inspire novel scientific ideas and artistic spirits. The exhibition will remain open to the public until December 20, 2015.
Professor Keon-Jae Lee Lectures at IEDM and ISSCC Forums
Professor Keon-Jae Lee of KAIST’s Materials Science and Engineering Department delivered a speech at the 2015 Institute of Electrical and Electronics Engineers (IEEE) International Electron Devices Meeting (IEDM) held on December 7-9, 2015 in Washington, D.C. He will also present a speech at the 2016 International Solid-State Circuits Conference scheduled on January 31-February 4, 2016 in San Francisco, California. Both professional gatherings are considered the world’s most renowned forums in electronic devices and semiconductor technology. It is rare for a Korean researcher to be invited to speak at these global conferences. Professor Lee was recognized for his research on flexible NAND chips. The Korea Times, an English language daily newspaper in Korea, reported on his participation in the forums and his recent work. An excerpt of the article follows below: “KAIST Professor to Lecture at Renowned Tech Forums” By Lee Min-hyung, The Korea Times, November 26, 2015 Recently he has focused on delivering technologies for producing flexible materials that can be applied to everyday life. The flexible NAND flash memory chips are expected to be widely used for developing flexible handsets. His latest research also includes flexible light-emitting diodes (LED) for implantable biomedical applications. Lee is currently running a special laboratory focused on developing new flexible nano-materials. The research group is working to develop what it calls “self-powered flexible electronic systems” using nanomaterials and electronic technology. Lee’s achievement with flexible NAND chips was published in the October edition of Nano Letters, the renowned U.S.-based scientific journal. He said that flexible memory chips will be used to develop wearable computers that can be installed anywhere.
Open KAIST 2015
KAIST’s research environment and its most recent achievements were open to the public. KAIST hosted “Open KAIST 2015” over two days from November 5-6, 2015 in which its 17 departments and three research centers were open to the public. The event is one of the largest events that KAIST holds, which permits such public viewings of its facilities. It is the eighth time it has taken place. During this event, the departments and centers offered 64 programs including laboratory tours, research achievement exhibitions, department introductions, and special lectures. The “Motion Capture System”of Professor Jun-Yong Noh’s lab (Graduate School of Culture Technology) drew particular attention. The “Motion Capture System” expresses human and animal motion in three-dimensional (3D) space using infrared cameras and optic markers, which can then be applied to various industries such as movies, games, and animation. During the program, researchers themselves demonstrated the recording of the movement and its conversion into 3D characters. Professor Yong-Hoon Cho’s laboratory introduced the scientific mechanism behind the Light Emitting Diode (LED) as well as its manufacturing process under the topic:“A to Z of LED Production.” The reserachers explained that how green LED is much more efficient compared to previous light sources and presented applications that how it is widely used in everyday life in smart phones, electronic displays, and other mobile gadgets. Professor Jun-tani of the Department of Electronic and Electrical Engineering introduced “Humanoid Robot Nao’s Imitation of Human Motions.” Nao is an autonomous, programmable humanoid robot developed by a French robotics company based in Paris. Nao has an artificial neural circuit, which is the functional equivalent of a human brain, and can thus mimic the subject’s motions through learning. In addition, Professor Hyo-Choong Bang (Department of Aerospace Engineering) in his lecture on “Unmanned Vehicle Research and Nano Satellites” and Professor Hyun Myung (Department of Civil and Environmental Engineering) on his lecture on “Future Civilization Robot System: the Jellyfish Elimination Robotic Swarm and the Wall-Climbing Drone” provided information on the progress of their respective research. KAIST also displayed its most recent research achievements. A lecture on “Information Technology Convergence” offered a showroom for “Dr. M,” which is a mobile healthcare platform. Dr. M is a mobile healthcare system that collects and analyzes biosignals via a smart sensor attached to the human body that shows around 20 advanced technologies. The Satellite Technology Research Center introduced the public to its “Get to Know Satellites” program on Korea’s first satellite “Our Star 1” in addition to showing the satellite assembly room and the satellite communication center. Special lectures were also held for visitors. Professor Min-Hyuk Kim and Hye-Yeon Oh of the School of Computing talked about “Computer Graphics and Advanced Video Technology” and “Man and the Computer,” respectively, from the perspective of non-experts. Another interesting feature was the “Wearable Computer Competition” in which college students held fashion shows with computers attached to their clothes. Professor Jung Kwon Lee, the Dean of the College of Engineering, who led this event, said that “the Open KAIST, which is being held for the eighth time this year, is an excellent opportunity for the general public to experience KAIST’s research environment.” He hoped this could motivate young adults to widen their spectrum of scientific knowledge and raise affection for science.
KAIST to Kick-Start the Exchange of Young Researchers with Northern European Universities
KAIST promotes research exchange and cooperation with three universities in Northern Europe. KAIST has signed a letter of intent (LOI) for the mutual exchange of young researchers and cooperation to collaborate with KTH Royal Institute of Technology and Lund University, both based in Sweden on June 2, 2015, and with Aalto University in Finland on June 4, 2015. This LOI was the result of the cooperative projects of Korea-Sweden and Korea-Finland Joint Committees on Science and Technology supervised by the Ministry of Science, ICT and Future Planning of Korea. As agreed in the LOI, KAIST will conduct joint research projects with the three universities by providing students and researchers with opportunities to visit each other through internship programs and workshops and by sharing information on education and research. Sung-Hyon Mayeng, the Associate Vice President of the International Relations Office at KAIST, said, “It’s an encouraging sign that universities and governments recognize the importance of increasing exchanges among academic and research communities. Expecting more vibrant relationships to be formed between KAIST and the three northern European universities in coming years, I hope that today’s agreement becomes a good basis to spur technological innovations that will not only benefit the regions but also the world.” Established in 1827, the KTH Royal Institute of Technology is the largest and oldest technical university in Sweden, accounting for one-third of the nation’s technical research and engineering education capacity at university level. The university offers education and research programs from natural sciences to all branches of engineering including architecture, industrial management, and urban planning. According to the QS World University Rankings in 2014, KTH Royal Institute of Technology ranked 27th in engineering and 1st in Northern Europe. Lund University, Sweden, is one of the oldest and most prestigious universities in northern Europe, consistently ranking among the world’s top 100 universities. In particular, its biological sciences and engineering have shown great strength, placing within the top 60 universities by the Times Higher Education (THE) World University Rankings. The university also receives the largest amount of research funding from the Swedish government. Aalto University in Finland was created as a merger of three leading Finnish universities: the Helsinki University of Technology (established 1849), the Helsinki School of Economics (established 1904), and the University of Art and Design Helsinki (established 1871). The university nurtures the close collaborations across science, business, and arts to foster multi-disciplinary education and research.
KAIST and the National Assembly of Korea Create a Committee to Plan "Patent Hub Korea"
The KAIST Graduate School of Future Strategy (GSFS) and the National Assembly of the Republic of Korea held a meeting at the National Assembly building in Seoul on September 23, 2014. At the meeting, the two organizations agreed to create a planning committee that will work for the construction of Korea as a global patent hub. In addition, the two also reviewed national laws and regulations related to patents and intellectual property rights (IPR) and discussed a future action agenda. Dean Kwang-Hyung Lee of GSFS, Chairman Ui-Hwa Chung of the National Assembly, Chairman Jong-Yong Yoon of the Presidential Council on Intellectual Property, and many representatives from the academia, government, and law participated in the meeting. Dean Lee, who is the co-chairman of the planning committee, said: “Although Korea has globally ranked number five in patents and IPR, it still suffers from the lack of relevant legal systems and professionals. I hope that the planning committee will serve as a catalyst to make Korea stronger in the field of intellectual property and to accelerate the creation of the Patent Hub Korea.”
The College of Information Science & Technology names its Alumnus of the Year 2014
The College of Information Science & Technology (CIST), KAIST, selected Tae-Kyung Yoo, the Chief Executive Officer of Lumens, Inc., a Korean company producing semiconductors and light emitting diodes (LEDs), as its Alumnus of the Year 2014. The award ceremony took place on September 19, 2014 at the KAIST Institute with the participation of the university’s senior management and students. Mr. Yoo was recognized for his pioneering work to develop the LED industry in Korea as the next-generation growth engine for the nation’s economy. After the ceremony, he gave a talk entitled “The Past and Future of the LED Industry: Its Important Role in the Change of Korean Industry.” The CIST created the Alumnus of the Year 2014 award, for the first time this year, to appreciate its alumni’s contribution to the advancement of the industrial and academic sectors of Korean information science and technology, and it will continue presenting the award from this year onwards.
Professor YongKeun Park Produces Undergraduate Students with International Achievements
Three undergraduate students under the supervision of Professor YongKeun Park from the Department of Physics, KAIST, have published papers in globally renowned academic journals. The most recent publication was made by YoungJu Jo, a senior in physics. Jo’s paper entitled “Angle-resolved light scattering of individual rod-shaped bacteria based on Fourier transform light scattering” was published in the May 28th edition of Scientific Reports. Analyzing bacteria is a very important task in the field of health and food hygiene, but using the conventional biochemical methods of analysis takes days. However, observation with Jo’s newly developed method using light scattering analyzes bacteria within a matter of seconds. SangYeon Cho from the Department of Chemistry also published papers in Cell (2012) and Nature (2013), respectively, under the guidance of Professor Park. SangYeon Cho’s outstanding research achievements were recognized by Harvard and MIT. He was accepted with a full scholarship to Harvard-MIT Health Sciences and Technology Graduate School. He will begin his graduate studies at Harvard-MIT this September. Last March, SeoEun Lee from the Department of Biology was the recipient of the Best Paper Award by the Optical Society of Korea. She plans to pursue a doctoral degree at the College of Physicians and Surgeons, Columbia University in New York. Professor Park said, “Undergraduate students, who are learning a variety of subjects concurrently, are at the most creative time of their lives. KAIST has offered many opportunities to undergraduate students to partake in various research programs.” - Picture (a) and (b): Rod-shaped bacteria’s phase image and light-scattering patterns - Picture (c): Quantitative analysis to illustrate the extraction of information from bacteria
World's Largest Web Conference To Be Held in Korea
The 2014 International World Wide Web Conference (WWW 2014), the world’s most prestigious academic conference in the field of web, will be held for the first time in Korea. The conference is to be last for five days at Seoul COEX, from 7th to 11th April. International World Wide Web Conference covers a wide range of web-related areas, including technologies, research papers, services and more. Since the first conference in 1994 in Switzerland, it has been held in various parts of North America, Europe, South America and Asia, attracting more than 1000 experts in the field. The 23rd International World Wide Web Conference is managed by the International World Wide Web Conferences Steering Committee (IW3C2) and co-hosted by KAIST and National Agency for Technology and Standards, as well as sponsored by Korea Information Science Society and the World Wide Web Consortium (W3C). Keynote speakers for this year’s conference include inventor of the World Wide Web, Sir Tim Berners-Lee, senior vice president of Microsoft, Dr. Qi Lu, and Carnegie Mellon University’s Prof. Christos Faloutsos, as well as Samsung Electronic’s vice president Jong-Deok Choi. In addition to WWW 2014, BigData Innovators Gathering (BIG 2014) and Web for Access (W4A 2014) is also to be held in joint. KAIST Computer Sciences Department’s Prof. Jinwan Jeong, in charge of directing this year’s conference, said “From one-sided 1st generation web to two-way 2nd generation web, such as blogs, and then recently to the 3rd generation web, which include social networks and semantic webs, the web technologies has grown vastly over the past 25 years. WWW 2014 will be the opportunity for Korea to discuss with the world about the informatization and future of the web.” Pre-registration for WWW 2014 can be applied at the official webpage for WWW 2014 (http://www2014.kr) before 17th February.
Technology Developed to Control Light Scattering Using Holography
Published on May 29th Nature Scientific Reports online Recently, a popular article demonstrated that an opaque glass becomes transparent as transparent tape is applied to the glass. The scientific principle is that light is less scattered as the rough surface of the opaque glass is filled by transparent tape, thereby making things behind the opaque glass look clearer. Professor Yong-Keun Park from KAIST’s Department of Physics, in a joint research with MIT Spectroscopy Lab, has developed a technology to easily control light scattering using holography. Their results are published on Nature’s Scientific Reports May 29th online edition. This technology allows us to see things behind visual obstructions such as cloud and smoke, or even human skin that is highly scattering, optically thick materials. The research team applied the holography technology that records both the direction and intensity of light, and controlled light scattering of obstacles lied between an observer and a target image. The team was able to retrieve the original image by recording the information of scattered light and reflecting the light precisely to the other side.This phenomenon is known as “phase conjugation” in physics. Professor Park’s team applied phase conjugation and digital holography to observe two-dimensional image behind a highly scattering wall. “This technology will be utilized in many fields of physics, optics, nanotechnology, medical science, and even military science,” said Professor Park. “This is different from what is commonly known as penetrating camera or invisible clothes.” He nevertheless drew the line at over-interpreting the technology, “Currently, the significance is on the development of the technology itself that allows us to accurately control the scattering of light." Figure I. Observed Images Figure II. Light Scattering Control
Professor Hwang Gyu Young Elected as Chairman of IEEE TCDE.
Professor Hwang Gyu Young (Department of Computer Science) was elected as the Chairman of IEEE (Institute of Electrical and Electronics Engineers) TCDE (Technical Committee on Data Engineering). IEEE TCDE is one of the three academic organizations (including VLDB Endowment, ACM SIGMOD) and Professor Hwang is the first to be elected as Chairman from the Asia-Pacific region. Professor Hwang’s tenure begins on New Year’s Day for two years. IEEE TCDE holds the world’s most prestigious academic competition IEEE ICDE and hosts the Working Group and publishes the IEEE Data Engineering Bulletin.
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