본문 바로가기
대메뉴 바로가기
KAIST
Newsletter Vol.25
Receive KAIST news by email!
View
Subscribe
Close
Type your e-mail address here.
Subscribe
Close
KAIST
NEWS
유틸열기
홈페이지 통합검색
-
검색
KOREAN
메뉴 열기
light
by recently order
by view order
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))
2016.12.01
View 9555
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).
2016.06.07
View 11945
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.
2015.11.26
View 8790
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.
2015.11.13
View 8797
Dr. Se-Jung Kim Receives the Grand Prize at the International Photo and Image Contest on Light
Dr. Se-Jung Kim of the Physics Department at KAIST received the Grand Prize at the 2015 Photo and Image Contest of the International Year of Light and Light-based Technologies. The United Nations has designated the year 2015 as the International Year of Light and Light-based Technologies. The Optical Society of Korea celebrated the UN’s designation by hosting an international photo and image contest on the theme of light and optics related technology. Dr. Kim presented a photo of images taken from a liquid crystal, which was entitled “A Micro Pinwheel.” She took pictures of liquid crystal images with a polarizing microscope and then colored the pictures. The liquid crystal has self-assembled circle domain structures, and each domain can form vortex optics. Her adviser for the project is Professor Yong-Hoon Cho of the Physics Department. Her work was exhibited during the annual conference of the Optical Society of Korea, which was held on July 13-15, 2015 at Gyeong-Ju Hwabaek International Convention Center. It will also be exhibited at the National Science Museum in Gwacheon and the Kim Dae-Jung Convention Center in Gwangju. Picture: A Micro Pinwheel
2015.07.31
View 8064
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.
2014.09.22
View 6840
Kinetic Lighting, Dlight, Dominates World Renowned Design Awards
Professor Sang-Min Bae “D’light,” a lamp that transforms its lampshade shape, developed by a team led by KAIST Department of Industrial Design’s Professor Sang-Min Bae, won Japan’s Good Design Awards on October the 2nd, soon after winning the internationally renowned 2013 International Design Excellence Awards (IDEA) in August. IDEA, sponsored by the Industrial Design Society of America (IDSA) and BusinessWeek, awards the best work from over 6,000 exhibits from 50 countries. Japan’s Good Design Awards, founded by the Japan Institute of Design Promotion (JDP) in 1957, is the most prestigious and one of the World’s four major design awards. “D’light” combines “donative” and “light.” Its meaning originates from the meaning of “delight” which means “giving great joy.” The shape and the brightness of the lamp can be transformed by turning the end of the heart-shaped lampshade. The team states that the lamp carries a figurative meaning of generous hearts lighting the neglected of the world by designing the lamp to be the brightest when it takes the shape of a heart. D’light developed as the 5th product of “the Nanum” project that started in 2006. Professor Bae first participated in the project in developing the 2nd product, “Cross Cube” in 2007. The he designed and launched the environmentally friendly humidifier “Lovepot” in 2008 and interactive tumbler “Hearty” in 2009. The “Nanum” project aims to develop innovative products for charity to create a humane social circulatory system. The project, led by the international relief and development organisation, World Vision and KAIST’s ID+IM laboratory run by Professor Bae, donates all profits to educate the children of low-income families. The project raised a total of 1.7 billion Korean won from 2007 this year to provide scholarships to 240 children in need. Professor Bae’s team has undertaken seed and “Nanum” projects with the theme of philanthropy design helping people in need by creating innovative designs. The project has produced four excellent and authentic products which received 44 world renowned design awards. Professor Bae said, “’The Nanum’ project consists of planning, designing, producing and selling for charity and donates all profit to children in need through education and scholarship.” He continued, “The consumers can purchase products that are aesthetically pleasing and convenient as well as gaining an opportunity to donate to children in need.” Figure1 Kinetic lighting D’light Figure 2. Characteristics of “Nanum” D’light The shape of the lampshade can be transformed. The lamp sheds the brightest light when it takes the shape of a heart, hence showing the figurative meaning of brightening the neglected parts of the world with generous hearts. Figure 3. Detailed Images of D’light
2013.11.11
View 8587
Transparent Glass Wall as a Touch Game Media
Professor Woo-hoon Lee - Selected as the “Highlight” at SIGGRAPH emerging technology conference - “An excellent example of the transparent display panel in everyday life” A joint research team led by KAIST Industrial Design Department’s Prof. Woo-hoon Lee and Computer Sciences Prof. Ki-hyuk Lee has developed a brand new concept game media “TransWall”, which utilizes both sides of the glass wall as the touch medium. TransWall has been chosen as the “highlight” of 2013 SIGGRAPH emerging technology conference. SIGGRAPH is a world-renowned conference in the area of computer graphics and interaction technique, last held 21st-25th July at Anaheim, in the United States. It all started with the thought, wouldn’t it be possible to turn the glass walls surrounding us into a medium for entertainment and communication? TransWall utilizes holographic screen film inserted between two glass sheets with a multi-touch function, onto which the image can be projected using the beam projector from both sides. Furthermore, an additional Surface Transducer attached to the glass can deliver the sound and vibration. What seemed as an ordinary glass wall has been transformed into a multi-sensory media that can transmit and receive visual, auditory and tactile information. TransWall can be implemented at public places such as theme parks, large shopping malls and subway stations, providing the citizens with a new form of entertainment. This touch-interaction method can also be applied to developing a variety of cultural contents in the future. Professor Lee said, “TransWall shows an example of near-future where touch-interaction method can be utilized with the soon-to-be commercialized transparent display panel in everyday lives.” TransWall Introduction video (https://vimeo.com/70391422) TransWall at SIGGRAPH 2013 Display (https://vimeo.com/71718874) Picture 1. Both sides of the glass wall can be used as a touch platform for various medias, including games. Picture 2. TransWall attracts the interests of the audience at SIGGRAPH emerging technology. Picture 3. Structure of TransWall Picture 4. Photo of TransWall from side
2013.09.19
View 8522
Using Light to Deliver Drugs to the Brain
The cerebral blood vessels have a unique blood-brain barrier. Using this unique structure, Professor Choi Chul Hee (Department of Bio-Brain Engineering) developed a technique to deliver drugs safely to the brain using lasers to alter the diffusivity of the blood-brain barrier. The blood-brain barrier allows the entry of only those drugs related to metabolic functions which made the entry of other drugs difficult. Due to this property it was difficult to administer the drug to a patient and have it affect the patient. Therefore the question was is it possible to maintain the effectiveness of the drug and allow it to pass through the barrier? The conventional method was to actually alter the structure of the drug or drill of small hole in the head and administering the drug directly, but these methods proved to be high risk and expensive. Professor Choi’s team used an ultra-short frequency laser beam on the barrier for 1/1000th of a second on the barrier to temporarily inhibit its function thereby allowing the drug to enter the brain safely.
2011.06.20
View 8243
A Light Weight, Energy Effcient Household Polysomnography (PSG) System Developed
A smart ‘household polysomnography (PSG) system’ was developed by domestic research team. Professor Yoo Hui Joon and his research team of KAIST’s department of Electricity and Electronic Engineering successfully developed a PSG system that is light weight and has high performance levels. The conventional PSG systems were complex with numerous lines and wires. The PSG is used to monitor biological signals during sleep and the monitored results are used to diagnose and cure sleep-related illnesses and disorders. However because of restrictions like the size of the machine, impurities, and the change in environment, multiple trials over several days were required to obtain accurate data. The system developed by the research team is lighter than a q-tip so as to not disturb the patient’s sleep. It also has Intelligent Circuit (IC) that detects when sensors come detached and automatically replaces the sensor with another sensor thereby allowing continual monitoring of the user. A low-power consuming circuit was implemented allowing the entire system to run continuously on a single coin battery for 10 hours which effectively decreased the weight of the system and simultaneously allows for uninterrupted monitoring of the user over the entire sleep cycle. Even a remote diagnosis system can be implemented. The user will don the PSG and sleep at home, ensuring that a normal heat beat rate, brain waves, breathing, etc. will be monitored. The data procured overnight can be sent to the experts online who will be able to diagnose remotely. The research team plans on performing research in cooperation with the KAIST hospital and U-Healthcare research. The research result is winning worldwide rave. The system was announced in the International Solid-State Circuits Conference (ISSCC) and was published in ISSCC magazine and in Japan’s NIKKEI Electronics January edition.
2011.03.25
View 10483
Soyeon's Odyssey by Space Travel, Feb. 1, 2011
Soyeon Yi, an alumna of KAIST who joined the Soyuz TMA-12 mission to the International Space Station in 2008 and successfully returned to the Earth after completion of her mission. She is often cited as the first Korean astronaut who had spaceflight. She recently had an interview with an Australian based online newspaper that publishes space related news stories. For the interview, please go to the link. http://www.space-travel.com/reports/Soyeon_Odyssey_999.html
2011.02.02
View 8593
Nanowerk Spotlight: Bacteria as environmentally friendly nanoparticle factories, Sep. 24, 2010
The Nanowerk.com is a leading portal site for nanotechnology and nanosciences, which runs a daily news section called “Spotlight.” On September 24, 2010, the Spotlight published an article on the latest developments of the research by a KAIST team headed by Distinguished Professor Sang-Yup Lee of the Chemical and Bimolecular Engineering Department. For the article, please click the link below: Nanowerk Spotlight: Bacteria as environmentally friendly nanoparticle factories, Sep. 24, 2010 By Michael Berger. http://www.nanowerk.com/spotlight/spotid=18188.php
2010.09.25
View 9680
<<
첫번째페이지
<
이전 페이지
1
2
3
>
다음 페이지
>>
마지막 페이지 3