Controlling the Local Electronic Properties of Si(553)-Au through Hydrogen Doping

Abstract

We propose a quantitative and reversible method for tuning the charge localization of Au-stabilized stepped Si surfaces by site-specific hydrogenation. This is demonstrated for Si(553)-Au as a model system by combining density functional theory simulations and reflectance anisotropy spectroscopy experiments. We find that controlled H passivation is a two-step process: step-edge adsorption drives excess charge into the conducting metal chain "reservoir" and renders it insulating, while surplus H recovers metallic behavior. Our approach illustrates a route towards microscopic manipulation of the local surface charge distribution and establishes a reversible switch of site-specific chemical reactivity and magnetic properties on vicinal surfaces.

Si(775)-Au atomic chains: Geometry, optical properties, and spin order

“…The spectrum exhibits a fairly weak positive peak at 1 eV and a broader negative feature in the 1.5 to 4.2 eV range. Qualitatively similar spectra have been observed on Si(557)-Au, Si(553)-Au, and Si(111)-Au [32,33]. For this class of surfaces, it is known that the 1.5-3.0 eV negative structure derives from transitions involving Si honeycomb chains.…”

“…Comparison of measured and calculated reflectance anisotropy spectra has been very helpful for identifying or discarding surface structural models [20]. RAS is particularly adept at distinguishing between similar quasi-1D surface reconstructions [29] and has previously been applied with success in the study of nominal Si(111)-Au and other vicinal Si(hhk)-Au systems [26,[30][31][32]. We thus carried out new experimental measurements of the RAS spectra of Si(775)-Au for different gold coverages and compared with calculations for the most stable models predicted in the previous section.…”

Spin pairing versus spin chains at Si(553)-Au surfaces

“…The Au chain at Si(553)-Au acts as an electron reservoir that readily provides and accepts charge, as recently established by hydrogen adsorption studies [35]. This finding suggests a surface energy lowering due to sp 3 → sp 2 + p rehybridization of every third Si edge atom, and subsequent charge transfer from the Si p orbital to the Au chain.…”

Organic Molecule Adsorption on Stepped Si–Au Surfaces: Role of Functional Group on Geometry and Electronic Structure

“…Various structural motifs are visible, namely Si step edges, Au chains, and honeycomb‐like Si plateaus. Recently we have investigated the sensitivity of these three different structural elements to the adsorption of atomic hydrogen and small thiol molecules on the vicinal Si(553)–Au surface . Favored bonding sites were investigated by computing the potential energy surface for adsorption of a methanethiol radical (CH 3 S·) prior to exploring the adsorption sites and geometry for a larger toluene‐3,4‐dithiol molecule.…”