One-Dimensional Potassium Chains on Silicon Nanoribbons

Silicon nanoribbons (SiNRs), characterized by a pentagonal structure composed of silicon atoms, host one-dimensional (1D) Dirac Fermions and serve as a minimalist atomic template for adsorbing various heteroatoms. Alkali-metal (AM) atoms, such as Na and K, with electronic structures comparable to those of hydrogen are of particular interest for such adsorption studies. However, the adsorption of AM atoms on SiNRs and its tunation on the properties of SiNRs have not yet been fully explored. In this study, we examined the adsorption of K atoms on high-aspect-ratio SiNRs and the resultant electronic properties using a combination of scanning tunneling microscopy (STM) and density functional theory calculations. K atoms prefer to adsorb on double- and multi-stranded SiNRs owing to the low adsorption energies at these sites. Each K atom and its three nearest Si atoms exhibit a triangular morphology resulting from charge transfer between K and Si atoms, as verified by theoretical calculations. As the K coverage of the SiNRs increased, the K atoms organize into 1D zigzag chains on the SiNRs. Moreover, K adsorption on the SiNRs was determined to be reversible. The deposition of K atoms on the SiNRs was achieved using a voltage pulse of the STM tip, without damaging the SiNRs structure. In addition, K adsorption effectively modulates the Dirac cone position of the SiNRs relative to the Fermi level. This study unveils the adsorption mechanism of AM atoms on SiNRs, providing a useful approach for heteroatom adsorption on other nanoribbons.

💡 Research Summary

In this work the authors investigate the adsorption behavior of potassium (K) atoms on silicon nanoribbons (SiNRs) that are epitaxially grown on Ag(110). SiNRs possess a pentagonal lattice and host one‑dimensional (1D) Dirac fermions, making them an ideal minimal template for studying heteroatom adsorption. The study combines low‑temperature scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and density functional theory (DFT) calculations to provide a comprehensive picture of how K atoms interact with SiNRs of different widths (single‑, double‑, and triple‑stranded ribbons, denoted SNR, DNR, and TNR respectively).

The SiNRs are prepared by depositing silicon on a clean Ag(110) surface held at 473 K for 16 minutes, yielding ribbons with widths of 0.8 nm (SNR), 1.6 nm (DNR) and 2.4 nm (TNR) and characteristic periodicities of 3, 5 and 7 surface unit cells along the