With the rapid development of modern information society, the size of devices becomes increasingly demanding. The realization of devices at atomic scale is expected to further improve their performance and miniaturization, and to continue the application of Moore's law. However, due to the limitation of processing technology, the development of atomic-scale devices faces serious challenges.
Recently, the research group of nanophotonics and single molecule-based devices, Institute of Modern Optics, College of Electronic Information and Optical Engineering, Nankai University, has proposed a new method for develop electronic switches at an atomic scale. Instead of applying the complicated processing technology of nanophotonics, it merely illuminates the junction of two electrodes with light, and use the heat generated by local surface plasmons (the collective resonance created by incident photons and free electrons on the metal surface) to heat the electrodes, so that they can connect and disconnect at an atomic scale by the effect of thermal expansion and contraction. Through controlling the light intensity or polarization and measuring conductance, the whole process of atoms breaking and reconnecting one after another is clearly demonstrated.
When the light illuminates the gap between nanoelectrodes, the light-excited heat is enhanced by the gap, resulting in tiny expansion of the electrodes. In this case, atomic switches can be realized by the expansion of nanoelectrodes due to plasmonic heating, and the gap size between two electrodes can be precisely adjusted with subangstrom accuracy. The dashed lines indicate the new position of the nanoelectrodes after expansion induced by plasmonic heating.
Typically, the energy loss caused by surface plasmonic heating will hinder the long-distance propagation of plasmons, and thus is regarded as an impediment for the application of surface plasmons, but the researchers and collaborators at the Institute of Modern Optics have produced new ideas to realize the effect of atomic switches by cleverly using the expansion of nanoelectrodes due to plasmonic heating, which can be accurately controlled. This idea of “turning waste into treasure” provides a new research platform for the studies of the excitation and transmission mechanism of surface plasmons. Also, the precisely adjustable angstrom gap can be applied in a variety of research fields, such as the fabrication of nanopore-based biosensors, tip-enhanced Raman spectroscopy and single-molecule transistors.
On March 27, the work was published online on one of Nature's series, Light: Science & Applications. The first author is Zhang Weiqiang, a 2016 postgraduate student from Institute of Modern Optics, College of Electronic Information and Optical Engineering, Nankai University. Professor Xiang Dong from Institute of Modern Optics, College of Electronic Information and Optical Engineering, Nankai University, Professor Xu Bingqian from University of Georgia in the U.S., and Professor Takhee Lee from Seoul National University in South Korea are the corresponding authors. The cooperative research units include State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Institute of Materials Research and Engineering, Singapore, and Research Center Juelich, Germany.