Hydrogenation-enriched fundamental properties of armchair silicene nanoribbons: a comprehensive first-principles study

In this study, density functional theory (DFT) calculations are systematically performed to explore structural, electronic, and magnetic properties of hydrogen-adsorbed 7-armchair silicene nanoribbons (7ASiNRs) with diverse hydrogenations, revealing unexpected physical behaviors. All optimized configurations exhibit good structural stability, whereas hydrogen atoms preferentially occupy top sites of Si atoms and double-side adsorption is energetically favored. Interestingly, although most even-hydrogenated configurations behave as nonmagnetic semiconductors with direct bandgaps, the (2H)_1-14 and (2H)_4-11 configurations exhibit anomalous magnetic moments, raising attention about the dependence of magnetism on the distance between adsorbed atoms. Moreover, the (7H)_single configuration shows a remarkably large magnetization of 7 <i>µ</i> _B, originating from unpaired Si-3p _<i>z</i> electrons localized on the unpassivated side. To clarify these phenomena, systematic analyses of orbital-, atom-, and spin-decomposed band structures, DOSs, charge, and spin density distributions are performed, demonstrating that the hybridization between H-1s and Si-(3s, 3p _<i>xy</i> , 3p _<i>z</i> ) orbitals govern the structural reconstructions, charge redistribution, and spin polarization. These findings uncover new mechanisms of magnetism and bandgap modulation in hydrogen-adsorbed 7ASiNRs, highlighting the essential role of hydrogen adsorption in tuning electronic and magnetic properties. The results provide valuable guidance for designing 2D silicon-based materials with controllable magnetic and electronic characteristics for future nanoelectronic and spintronic device applications.