Ultra-thin epitaxial metallic films on semiconductors – A playground for exploration of novel quantum phenomena at nanoscale

When an electronic system is confined in one or more dimensions to a length scale comparable to the de Broglie length, quantum confinement occurs. Such confinements have played central role in artificially engineered electronic systems such as quantum wells, wires, dots and related structures. For semiconductors, quantum confinements occur at a length scale somewhere around 100 nm. For metals, however, they occur at a length scale about one to two orders of magnitude smaller (1-5 nm). Investigations of quantum size effects in ultra-thin metallic films have recently gained tremendous amount of interests. These renewed interests are largely driven by the advancement in atomic scale control in epitaxial growth of metallic thin films, thus making it possible to access this strongly confined regime. In this presentation, we describe several interesting phenomena resulting from the confinement of electronic waves in metallic nanostructures. These include: (a) quantum size effect on nanostructure formation, (b) quantum size effect on workfunction of nanostructures, (c) quantum size on effect on superconductivity.