2025/03/16 by Yuke Song, Song, Yuke, ShiFang Li +10
Engineering · Materials Science · Physics and Astronomy · #Advanced Materials Characterization Techniques #Electron and X-Ray Spectroscopy Techniques #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Surface and Thin Film Phenomena
paper · pdf · doi:10.48550/arxiv.2503.12324
openalex publication_date 2025/03/16 · openalex created_date 2025/10/19 · openalex updated_date 2026/07/28
The 7x7 reconstruction of Si(111) surface is widely understood by the dimer-adatom-stacking-fault model (DAS), but the predicted metallicity of DAS contradicts experimental signs of insulation. It is still challenge to predict DAS-like reconstructions by traditional method to solve such a puzzle. Here, we show that low-energy reconstructions of Si(111)-7x7 surface with (DAS-d8-T12, DAS-d8-T9H3-A, DAS-d8-T9H3-B and DAS-d8-T6H6) and without (AB-d10-T12, AB-d10-T9H3, AA-d10-T12 and AA-d10-T9H3) stacking-fault can be quickly discovered by graph theory as implemented in RG2 code for crystal structure prediction. They exhibit comparable stability to the DAS (DAS-d8-T12) model and similar STM patterns, offering a plausible explanation for the observed Si(111)-7x7 reconstruction. All these reconstructions exhibit metallic behavior in the nonmagnetic (NM) state with isolated narrow bands crossing the Fermi level in varying occupancy. And they are further confirmed as ferromagnetic (FM) metals (DAS-d8-T9H3-B), half-metals (DAS-d8-T12, AB-d10-T9H3, AA-d10-T12 and AA-d10-T9H3), half-semimetals (DAS-d8-T9H3-A and DAS-d8-T6H6) and even insulators (AB-d10-T12), depending their occupancies of the NM band structures. These findings not only demonstrate the rich electromagnetic phases of reconstructed Si(111) surfaces and their potential for spintronic applications, but also provide a plausible physical explanation for the metal-insulator transition observed on the Si(111) surface.