Change of Electronic Structures by Dopant-Induced Local Strain

Abstract

Ag-induced Si(111)- surfaces (-Ag) exhibit unusual electronic structures that cannot be explained by the conventional rigid band model and charge transfer model. The (-Ag surfaces feature a free-electron-like parabolic band, the S1 band, that selectively shifts downward upon the adsorption of noble metal or alkali metal adatoms. Furthermore, the downward shift of S1 is independent of the type of dopants, Au, Ag, and Na. According to charge transfer analysis, Au adatoms accumulate electrons from the substrate and become negatively charged, whereas Na adatoms become positively charged, which indicates that S1 should shift in the opposite direction for both the adatoms. Investigation of calculated structures, calculation of model structures, and tight-binding analysis disclose that the changes in the electronic structure are closely related to the average Ag-Ag distance in the substrate and have their origin in the local strain induced by dopants (adatoms). This explanation implies that the electronic structure is irrespective of the dopant characters itself and paves a new way for understanding the electronic structures associated with the presence of dopants.

Probing Sodium Storage Mechanism in Hollow Carbon Nanospheres Using Liquid Phase Transmission Electron Microscopy

“…The distinct bandgap opening at 4.5 eV indicates a change in electronic structure due to induced local strain from Na(0) in the micropores. [72] The contact between the metallic sodium layer deposited on the inner surface of N-PHCSs and the semiconductor-like carbon shell forms the metal-semiconductor junction in the N-PHCSs. [60,62] The EFTEM analysis of freestanding N-PHCSs was conducted over a selective energy range before and after sodiation (Figure 5c-f) to resolve the spatial distribution of these featured signals.…”