Hanging by a thread: Imaging and probing chains of single atoms

(Press-News.org) Ishikawa, Japan - Today, many well-studied materials in various fields, such as electronics and catalysis, are close to reaching their practical limits. To further improve upon modern technology and outperform state-of-the-art devices, researchers looking for new functional materials have to push the boundaries and explore more extreme cases. A clear example of this is the study of low-dimensional materials, such as monoatomic layers (2D materials) and monoatomic chains (1D materials).

It has been proved time and time again that low-dimensional materials exhibit exotic properties that are absent in their 3D bulk counterparts. For example, monoatomic chains of metals like gold and platinum (Pt) can exhibit the contribution of certain quantum phenomena, such as magnetic order or thermal transport, in ways that could find practical applications. However, it is very difficult to experimentally observe what goes on in monoatomic chains composed of five or less atoms, and the mechanical properties of single-atom bonds remain elusive.

To tackle this issue, a research group lead by Professor Yoshifumi Oshima from Japan Advanced Institute of Science and Technology (JAIST), Japan, is pioneering a novel and promising technique to measure the strength of individual atomic bonds. Their latest study, which was published in Nano Letters and showcased their strategy, involved researchers from JAIST (Dr. Zhang, Dr. Ishizuka, Prof. Tomitori, Prof. Maezono and Prof. Hongo), as well as Prof. Arai from Kanazawa University and Prof. Tosatti from the International School for Advanced Studies (SISSA) and The Abdus Salam International Centre for Theoretical Physics (ICTP).

This new technique, which Oshima named the "microscopic nanomechanics measurement method," combines transmission electron microscopy (TEM) with a quartz length-extension resonator (LER). TEM is a widely used imaging technique with incredibly high spatial resolution--enough to make out individual atoms--whereas the LER is a device that can oscillate at incredibly small amplitudes of a few ten trillionths of a meter and serves as a force sensor.

The researchers devised an experimental setup in which a small Pt juncture was stretched to its absolute breaking point, that is, when the two pieces of Pt were linked by a monoatomic chain of two to five atoms. By carefully aligning the pieces in the TEM, they observed the formation and breaking of the monoatomic Pt chains in real time. Moreover, using the quartz LER, they measured the conductance across the chain and its stiffness, from which the strength of individual Pt bonds was calculated with success. "We found the bond strength of 25 N/m in the monoatomic Pt chains to be remarkably high, especially compared to the 20 N/m normally found in bulk Pt crystals," comments Zhang. ""Moreover, these single-atom bonds could be stretched about 24% of their regular distance, in stark contrast to the 5% that bonds between Pt atoms in bulk can be stretched," he adds.

The results of the study showcase the potential of this novel technique to probe monoatomic chain bonds, which could lead to a better understanding of the interfaces or surfaces of low-dimensional materials. "Our method could greatly contribute to the design of advanced materials and catalysts as well as shed light on nanoscale phenomena in terms of surface or interface nanomechanics," highlights Oshima. In turn, more sophisticated materials and a better understanding of their surface properties will undoubtedly advance the fields of electronics, chemistry, and nanotechnology, paving the way to innovative and hopefully sustainable designs.

It's very likely that the expression "hanging by a thread" will soon get a more positive meaning in nanomaterials science!

INFORMATION:

About Japan Advanced Institute of Science and Technology, Japan Founded in 1990 in Ishikawa prefecture, the Japan Advanced Institute of Science and Technology (JAIST) was the first independent national graduate school in Japan. Now, after 30 years of steady progress, JAIST has become one of Japan's top-ranking universities. JAIST counts with multiple satellite campuses and strives to foster capable leaders with a state-of-the-art education system where diversity is key; about 40% of its alumni are international students. The university has a unique style of graduate education based on a carefully designed coursework-oriented curriculum to ensure that its students have a solid foundation on which to carry out cutting-edge research. JAIST also works closely both with local and overseas communities by promoting industry-academia collaborative research.

About Professor Yoshifumi Oshima from Japan Advanced Institute of Science and Technology, Japan Yoshifumi Oshima received Ph.D. and Master's degrees from Tokyo Institute of Technology, Japan, where he worked from 1995 to 2010 as an Assistant Professor. He joined JAIST in as an Associate Professor in 2014 and become a full Professor in 2018. He currently leads the Oshima Lab, which specializes in thin-film surfaces and interfaces, solid-state physics, nanomaterials, and nano-contact physics. He has about 200 published papers and authored two books.

Funding information This work was supported by JSPS KAKENHI (grant nos. 18H01825 and 18H03879). The computations in this work were performed using the facilities of the Research Center for Advanced Computing Infrastructure at JAIST. Jiaqi Zhang acknowledges financial support by the Sasakawa Scientific Research Grant from The Japan Science Society and the Exchange Research Grant Project from Marubun Research Promotion Foundation. Erio Tosatti acknowledges support by ERC ULTRADISS Contract No. 834402, and the Italian Ministry of University and Research through PRIN UTFROM N. 20178PZCB5.