A South Korean research team has developed a materials-design method that adds new functions while preserving a material’s inherent strengths, achieved simply by changing the order in which the same types and amounts of atoms are stacked. It is regarded as a core technology that could lead to next-generation electronic devices, semiconductor insulating films, and thermal sensors.
 [코리안투데이] A schematic illustrating the realization of polarity through a selective atomic gradient, together with atomic-resolution electron microscopy images © 장형임 기자 |
The Ministry of Science and ICT (Minister and Deputy Prime Minister Bae Kyung-hoon) announced that a joint research team comprising Professors Daesu Lee, Gil-Ho Lee, and Si-Young Choi of Pohang University of Science and Technology (POSTECH) and Professor Se Young Park of Soongsil University had precisely designed the compositional arrangement of atomic layers to realize new functions in metals and ultrathin insulating materials. The findings were published in Science, the world’s most prestigious academic journal, on October 2 (local time: 2 p.m. EDT, Thursday, October 1). The paper is titled ‘Synergistic polar states by selective atomic gradients.’
Until now, functional materials have mainly been created by mixing in new elements or changing the proportions of existing ones. However, because a material’s original functions can change or disappear in the process of acquiring new properties, adding functions while keeping existing strengths has not been easy. In metals in particular, it has been difficult to simultaneously maintain good electrical conductivity and realize ‘polarity,’ in which atoms are arranged with a bias toward one direction. In ultrathin insulating materials, the thinner they become, the more current leaks out, making it difficult to secure a thin thickness and high insulating performance at the same time.
The team devised a design method called the ‘Selective Atomic Gradient,’ which leaves the atoms related to a material’s electronic properties untouched while slightly varying the proportion of specific atoms of different sizes from one atomic layer to the next along the thickness direction. Much like a gradation in which colors gradually change, introducing differences in atomic proportions along the thickness direction caused the atoms to tilt slightly to one side, forming polarity within the material. Reversing the stacking order of the atomic layers reversed the direction of the polarity as well, and no such directionality appeared in materials where the same types and amounts of atoms were mixed uniformly.
The team first applied the design method to a highly conductive (Sr,Ca)IrO₃ metal thin film. As a result, while the material retained its metallic character, its resistance differed depending on whether current flowed in one direction or the opposite, and reversing the stacking order of the atomic layers also reversed the direction of the resistance difference. This confirmed that a material’s electrical directionality can be controlled at the fabrication stage.
Next, when the same method was applied to a (Ba,Ca)TiO₃ ultrathin insulating material about 5.1 nanometers (nm) thick, the leakage current passing through the film was greatly reduced while its ability to store electrical energy was maintained at a high level. Notably, its performance in converting temperature changes into electrical signals was about 100 times higher than that of a representative comparison film of similar thickness, and reversing the stacking order of the atomic layers also reversed the direction of the electrical signal generated by temperature changes.
The significance of this achievement lies not in the discovery of a single high-performance new material, but in presenting ‘the order in which atoms are stacked’ as a new variable for materials design. By confirming that the same principle works in both highly conductive metals and nearly non-conductive insulating materials, the team demonstrated broad applicability. The researchers expect the technology to be used in electronic devices that operate differently depending on the direction of current, as well as in spintronics, next-generation semiconductor ultrathin insulating films with reduced leakage current, infrared and thermal sensors that detect temperature changes, and energy-harvesting technologies.
Professor Daesu Lee, who led the research, said, ‘We have proven that new functions can be added while preserving a material’s original strengths, simply by changing the order in which atoms are stacked, without adding any new elements.’ He added, ‘Going forward, we plan to extend this method to a wider range of materials, such as magnetic materials and superconductors, and to carry out follow-up research to implement it in actual devices such as ultrathin insulating films and thermal sensors.’
Kim Sung-soo, Director-General of the R&D Policy Bureau at the Ministry of Science and ICT, said, ‘This achievement shows how basic research exploring the fundamental properties of matter can lead to new solutions in materials design.’ He added, ‘We will spare no support for basic research so that researchers can explore new principles based on creative ideas and continue to pursue challenging work.’
This research was conducted with support from the Ministry of Science and ICT’s basic research programs (Core Research and Leading Research Centers). The corresponding authors of the paper are Professors Daesu Lee, Gil-Ho Lee, Si-Young Choi, and Se Young Park, and the first authors are POSTECH integrated-course students Sang-Hyeon Kim and Ki-Jeong Han, along with Dr. Su-Yoon Hwang and Dr. Ga-Hee Noh. Inquiries may be directed to Professor Daesu Lee of the Department of Physics at POSTECH (054-279-2063) or to the Basic Research Promotion Division of the Ministry of Science and ICT (044-202-4530).
지역 홍보대사 신청 기자양성과정 신청 코리안투데이 지부장 신청 코리안투데이 인천강화코리안브랜드대상 신청 최고경영인대상 신청 소비자만족도대상 신청
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