By means of first-principles density functional theory calculations, we findthat hydrogen-passivated ultrathin silicon nanowires (SiNWs) along [100]direction with symmetrical multiple surface dangling bonds (SDBs) and borondoping can have a half-metallic ground state with 100% spin polarization, wherethe half-metallicity is shown quite robust against external electric fields.Under the circumstances with various SDBs, the H-passivated SiNWs can also beferromagnetic or antiferromagnetic semiconductors. The present study not onlyoffers a possible route to engineer half-metallic SiNWs without containingmagnetic atoms but also sheds light on manipulating spin-dependent propertiesof nanowires through surface passivation.
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