Surface plasmon driven atomic migration mediated by molecular monolayer

Highly efficient controlling the individual atomic migration is the basis of the modern atomic manufacturing. Although one-by-one atom migration can be realized precisely by STM technique, such a delicate operation is time consuming and restrictive conditions (e.g., high-vacuum) is required.

A research team from the Institute of Modern Optics and the Center for Single Molecule Science at Nankai University, China, has now reported a breakthrough method to achieve efficient atomic migration under room temperature and atmospheric conditions. Their study, titled “Surface Plasmon Driven Atomic Migration Mediated by Molecular Monolayer,” was recently published in PhotoniX.

By introducing a self-assembled molecular monolayer (SAM) into a nanoparticle-on-mirror (NPoM) structure, the team used pulsed laser excitation to drive the migration of metal atoms (Fig. 1a). The process is mediated not by optical gradient forces, but by dipole–dipole interactions between the molecular tips and surface atoms, induced by localized surface plasmons (LSP). As illustrated in Fig. 1b, laser irradiation induces a redshift in the scattering spectrum of the NPoM structure, accompanied by a visible colour change in dark-field images, confirming the structural modification due to atomic migration (Fig. 1c).

Systematic experiments showed that both the type of molecule and laser power jointly regulate atomic migration. For example, molecules with higher polarizability strongly promote atom movement, while photochemical conversion of molecules with lower polarizability weakens the effect (Figs. 2a-e). Under high-power laser irradiation, certain molecules undergo chemical transformation, which in turn influences the resonance shift and migration behaviour (Figs. 2f-h).  These findings were verified using dark-field scattering spectroscopy, in-situ Raman, and scanning electron microscopy.

Beyond mechanism discovery, the team demonstrated a practical pathway to fabricate atomic-scale arrays. The overall fabrication process is summarised in Fig.3. By assembling SAMs on metal films, depositing nanoparticles, and irradiating with laser light, atoms migrate laterally to form symmetric atomic islands. Removing the nanoparticles leaves behind stable atomic patterns, offering a new approach for large-scale atomic manufacturing.

This research not only unveils a new mechanism of molecule-assisted atomic migration but also introduces a scalable, efficient method for atomic patterning under ambient conditions. The findings hold promise for future applications in plasmonics, surface-enhanced Raman spectroscopy, atomic manufacturing, catalysis, and molecular-scale electronics.

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