Substrate for atomic chain electronics

Abstract

A substrate for future atomic chain electronics, where adatoms are placed at designated positions and form atomically precise device components, is studies theoretically. Since the van der Waals force turns out inappropriately weak, adatoms have to be secured with chemical bonding to the substrate atoms, but then electronic isolation between the adatom and substrate systems is not always guaranteed. A chain model shows that good isolation is expected on an $s\ensuremath{-}p$ crossing substrate such as Si, Ge, or GaAs through surface localization, reflecting the bulk nature of the substrate. Isolation is better if adatoms are electronically similar to the substrate atoms, and can be manipulated by hydrogenation. Chain structures with group IV adatoms with two chemical bonds, or group III adatoms with one chemical bond, are semiconducting, reflecting the surface nature of the substrate. These structures are unintentionally doped due to the charge transfer across the chemical bonds. Physical properties of adatom chains have to be considered for the unified adatom and substrate systems.