Self-adsorption of an Ultrathin Bismuth Layer in the Size of Ions on an Au Surface

Molecular self-assembly is an important aspect of bottom-up approaches for the nanofabrication of functional materials. The self-assembly of smaller-size units like ions has yet to be studied further. The self-adsorption of Bi III without applied potential and electrochemical deposition of Bi/Bi III were studied and compared through cyclic voltammetry. Both of them exhibit two pairs of redox peaks assigned to the (2 × 2)-Bi adlayer and incommensurate ( p  × √3)-2 Bi adlayer. The adsorption of two Bi surface phases is related with the Bi salt concentration and adsorption time. Within a certain concentration or time range, the adsorption approaches to be saturated due to the surface limitation of self-adsorbed surface layers. The (2 × 2)-Bi adlayer firstly adsorbs to the active sites of Au where there is strong interaction between Bi and Au. With the increase of time, more Bi adsorbs onto the unoccupied sites of Au with a relatively weak interaction force to form a denser ( p  × √3)-2 Bi layer. A new pair of redox peaks appears for the electrodeposition of the Bi/Bi III bulky layer which is easily stripped from the Au surface through a consecutive potential scan. Comparatively speaking, the adsorbed (2 × 2) and ( p  × √3)-2 Bi adlayers are stable in the same potential scanning condition due to the strong interaction between the two surface Bi layers and the below Au atoms. Such a controllable self-adsorption of the Bi III ultrathin layer on foreign substrates exhibits a potential for the modification of materials in the size of ions.