Quantum Size Effects in the Growth and Properties of Ultrathin Metal Films, Alloys, and Related Low-Dimensional Structures

This chapter addresses the quantum mechanical nature of the formation, stability, and properties of ultrathin metal films, metallic alloys, and related low-dimensional structures, with Pb as a primary elemental example. The emphasis is on the contribution to the overall energetics from the electronic degrees of freedom of the low-dimensional systems. As a metal film reduces its thickness, the competition between quantum confinement, charge spilling, and Friedel oscillations, all of electronic origin, can dictate whether an atomically smooth film is marginally, critically, or magically stable or unstable against roughening during the growth of such metal films. The “electronic growth” mode as emphasized here serves as an intriguing addition to the three well-established classic modes of crystal growth. In exploring electronic growth, Pb(111) films represent a particularly compelling example, not only because their stability exhibits unusually strong quantum oscillations but also because their physical and chemical properties can be tuned with great precision by controlling the film thickness or the chemical composition. Recent advances and the perpectives in this active area of film growth will be reviewed, with results from both theoretical and experimental studies.