nanostructures
-
Novel Material Properties of Hybrid Perovskite Nanostructures for Next-generation Non-linear Electronic Devices
(from left: Juho Lee, Dr. Muhammad Ejaz Khan and Professor Yong-Hoon Kim)
A KAIST research team reported a novel non-linear device with the founding property coming from perovskite nanowires. They showed that hybrid perovskite-derived, inorganic-framework nanowires can acquire semi-metallicity, and proposed negative differential resistance (NDR) devices with excellent NDR characteristics that resulted from a novel quantum-hybridization NDR mechanism, implying the potential of perovskite nanowires to be realized in next-generation electronic devices.
Organic-inorganic hybrid halide perovskites have recently emerged as prominent candidates for photonic applications due to their excellent optoelectronic properties as well as their low cost and facile synthesis processes. Prominent progresses have been already made for devices including solar cells, light-emitting diodes, lasers and photodetectors.
However, research on electronic devices based on hybrid halide perovskites has not been actively pursued compared with their photonic device counterparts.
Professor Yong-Hoon Kim from the School of Electrical Engineering and his team took a closer look at low-dimensional organic-inorganic halide perovskite materials, which have enhanced quantum confinement effects, and particularly focused on the recently synthesized trimethylsulfonium (TMS) lead triiodide (CH3)3SPbI3.
Using supercomputer simulations, the team first showed that stripping the (CH3)3S or TMS organic ligands from the TMS PbI3 perovskite nanowires results in semi-metallic PbI3 columns, which contradicts the conventional assumption of the semiconducting or insulating characteristics of the inorganic perovskite framework.
Utilizing the semi-metallic PbI3 inorganic framework as the electrode, the team designed a tunneling junction device from perovskite nanowires and found that they exhibit excellent nonlinear negative differential resistance (NDR) behavior. The NDR property is a key to realizing next-generation, ultra-low-power, and multivalued non-linear devices. Furthermore, the team found that this NDR originates from a novel mechanism that involves the quantum-mechanical hybridization between channel and electrode states.
Professor Kim said, “This research demonstrates the potential of quantum mechanics-based computer simulations to lead developments in advanced nanomaterials and nanodevices. In particular, this research proposes a new direction in the development of a quantum mechanical tunneling device, which was the topic for which the Nobel Laureate in Physics in 1973 was awarded to Dr. Leo Esaki.
This research, led by Dr. Muhammad Ejaz Khan and PhD candidate Juho Lee, was published online in Advanced Functional Materials (10.1002/adfm.201807620) on January 7, 2019.
Figure. The draft version of the cover page of 'Advanced Functional Materials'
2019.02.22 View 6584 -
The MSE/CBE Int'l Workshop Explores Big Ideas in Emerging Materials
(KAIST President Sung-Chul Shin with scholars participated in the workshop)
The MSE/CBE International Workshop brought together editors from key academic journals in multidisciplinary materials science and scholars from leading universities at KAIST on Aug. 7.
The workshop hosted ten distinguished speakers in the fields of nanostructures for next-generation emerging applications, chemical and bio-engineering, and materials innovation for functional applications. They explored opportunities and challenges for reinventing novel materials that will solve complex problems.
(From left: Professor Buriak, Professor Swager and Professor Il-Doo Kim)
Speakers included: Chief Editor of Nature Materials Vincent Dusastre; Editor-in- Chief of ACS NANO and professor at UCLA Paul S. Weiss; Jillian M. Buriak, Editor-in-Chief of Chemistry of Materials; Associate Editor of Macromolecules and professor at MIT Timothy M. Swager; Coordinating Editor of Acta Materialia and Head of the Department of Materials Science and Engineering at MIT Christopher A. Schuh; Editor-in-Chief of Biotechnology Journal and Metabolic Engineering and Distinguished Professor at KAIST Sang-Yup Lee; Associate Editor of Energy Storage Materials and professor at KAIST Sang Ouk Kim; Professor Jeffrey C. Grossman at MIT; Professor Zhenan Bao at Stanford University; and Professor Hyuck Mo Lee, head of the Department of Materials Science and Engineering at KAIST.
Interdisciplinary materials research holds the key to building technological competitiveness in many industrial sectors extending from energy, environment, and health care to medicine and beyond. It has also been the bedrock of KAIST’s scholarship and research innovation. More than 200 faculty members in the field of materials science produce about 800 SCI papers every year. The two departments of materials science and chemical biomolecular engineering are leading KAIST’s global reputation, as they were both ranked 13th and 14th in the QS World University Ranking by Subject this year.
(Professor Il-Doo Kim fromt he Department of Materials Science Engineering)
Professor Il-Doo Kim from the Department of Materials Science Engineering has been the chair of this workshop from 2016. In hosting the second one this year, he said that he hopes this year’s workshop will inspire many materials scientists to have big ideas and work to make those big ideas get noticed in order to have a real impact.
(KAIST President Sung-Chul Shin)
President Sung-Chul Shin, who is a physicist specializing in materials physics, expressed his keen interest in the workshop, saying innovative materials made of unthinkable and noble combinations will be the key factor in determining the competitiveness of new technology and new industries. He lauded international collaborations for making new materials and the scholarly passion to evaluate the materials’ characteristics that made this significant progress possible.
Dr. Vincent Dusastre, chief editor of Nature Materials, presented recent trends in materials for energy. He described how the rational design and improvement of materials’ properties can lead to energy alternatives which will compete with existing technologies. He pointed out that given the dramatic fundamental and practical breakthroughs that are taking place in the realization of solar cells with high energy-conversion efficiency, the improvement of batteries for electric vehicles and the grid is also a major challenge. He stressed, “Key advances in sustainable approaches beyond Li-ion batteries and control of redox processes are also greatly needed.”
Meanwhile, ACS NANO Editor-in-Chief Paul S. Weiss spoke on the importance of heterogeneity in the structure and function of molecules and nanoscale assemblies. He stressed that such extensiveness of multi-interdisciplinary research will accelerate a greater impact as indicated when the fields of neuroscience and microbiome converged with nanoscience and nanotechnology.
Editor-in-Chief of Chemistry of Materials Professor Jillian M. Buriak from the University of Alberta described how predictive models and machine learning can replace time consuming empirical device production and screening. By understanding and pinpointing the frustrating bottlenecks in the design of stable and efficient organic photovoltaics, much faster throughput can be obtained to enable a more direct pathway to stability, efficiency, and finally commercialization.
2018.08.13 View 10990 -
A Molecular Switch Controlling Self-Assembly of Protein Nanotubes Discovered
International collaborative research among South Korea, United States, and Israel research institutionsThe key to the treatment of cancer and brain disease mechanism The molecular switch that controls the self-assembly structure of the protein nanotubes, which plays crucial role in cell division and intracellular transport of materials, has been discovered. KAIST Bio and Brain Engineering Department’s Professor Myeong-Cheol Choi and Professor Chae-Yeon Song conducted the research, in collaboration with the University of California in Santa Barbara, U.S., and Hebrew University in Israel. The findings of the research were published in Nature Materials on the 19th. Microtubules are tube shaped and composed of protein that plays a key role in cell division, cytoskeleton, and intercellular material transport and is only 25nm in diameter (1/100,000 thickness of a human hair). Conventionally, cancer treatment focused on disrupting the formation of microtubules to suppress the division of cancer cells. In addition Alzheimer’s is known to be caused by the diminishing of structural integrity of microtubules responsible for intercellular material transport which leads to failure in signal transfer. The research team utilized synchrotron x-ray scattering and transmission electron microscope to analyze the self assemble structure of protein nanotubes to subnanometer accuracy. As a result, the microtubules were found to assemble into 25nm thickness tubules by stacking protein blocks 4 x 5 x 8nm in dimension. In the process, the research team discovered the molecular switch that controls the shape of these protein blocks. In addition the research team was successful in creating a new protein tube structure. Professor Choi commented that they were successful in introducing a new paradigm that suggests the possibility of controlling the complex biological functions of human’s biological system with the simple use of physical principles. He commented further that it is anticipated that the findings will allow for the application of bio nanotubes in engineering and that this is a small step in finding the mechanism behind cancer treatment and neural diseases.
2014.02.03 View 9800