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Welcome to the Atomic-Scale Microscopy & Spectroscopy Group!
This group utilizes low-temperature scanning probe microscopy (SPM) that visualizes individual atoms and molecules in real space. We also perform localized spectroscopic measurements by irradiating the SPM junctions with laser light. This provides information on the sub-nanometer scale beyond the simple topography. The goal of this group is to understand the origin of characteristic chemical/physical phenomena at solid material surfaces and molecules adsorbed on the surfaces at the atomic level by high spatial resolution imaging and spectroscopy techniques.
News
Publication: Single-molecule-level vibrotational spectroscopy for hydrogen
May 2025

Our letter published in Physical Review Letters demonstrates the usefulness of tip-enhanced Raman spectroscopy (TERS) in characterizing physisorption systems. Weakly adsorbbed molecules, such as hydrogen on metal surfaces, are difficult to visualize even with scanning tunneling microscopy. Nevertheless, a plasmon-enhanced molecular spectroscopy technique called TERS well detects physisorbed hydrogen at the tip-sample junction. By analizing the vibrational/rotational spectra, we can also learn about the optical properties of the local tip-sample junction. Unlike previous TERS-measurement targets, the physisorption system exhibits poor chemical enhancement. Instead, the ultraconfined electromagnetic field at the atomic-scale local junction, namely, a plasmonic picocavity, dominates the Raman signal enhancement.
New group member: Hyeji Choi
May 2025

I am pleased to welcome Hyeji to our group as a doctral candidate. She works on single-molecule measurements using ultrahigh-vacuum low-temperature scanning probe microscopy. I wish her success!
Two posters from us brought prizes!
Oct 2024

In an international conference, The 10th International Symposium on Surface Science (ISSS-10), Dr. Youngwook Park won Young Researcher Prize for his poster on the control of single-molecule photoswitching, and Mr. Kyungmin Kim, who visited us last year, also won Student Prize for his poster on tip-enhanced Raman spectroscopy measurements he conducted here. Their poster presentations were indeed remarkable. Congratulations, Youngwook and Kyungmin!
Publication: Plasmon-induced switch of a single molecule on silicon
Aug 2024

Our research on nano-optoelectronics has been published in Nature Communications. Plasmons, nanoscale confined light, are promising as triggers for photochemical reactions and optoelectronic devices in the single- or even sub-molecular level, but the precise control of them remains challenging. By subnanoscale positioning of a silver tip with plasmon resonance, we controlled a photoswitch of a single-anhydride-molecule/silicon-surface system where chemical bonding between molecular O atoms and surface Si atoms are ruptured and formed repeatably by the plasmons. What is the role of the silicon surface? What kind of molecules can be switched? How can we achieve a sustainable switch? We addressed these issues in the article, which should significantly contribute to future design and control of ultimately minitualized photodevices.
A poster prize winner here!
May 2024

Max Halbauer won a poster prize at a seminar he attended (809. WE-Heraeus-Seminar, Bad Honnef). This is his first academic award, but I am confident that this is just the beginning of his many accomplishments! Congratulations, Max!