Seminars Archive

The properties of Be(10-10)

Abstract
Beryllium is a simple metal on the verge of being a semiconductor: the electronic density of states has a minimum at the Fermi level and the bonding is highly directional. The (0001) and (10-10) surfaces of Be still, however, have a high local density of states at the Fermi level caused by the presence of surface states. Hence, these surfaces may be viewed as a model for quasi two-dimensional metals. The electronic structure of the two Be surfaces is very different: while the closed packed (0001) surface supports a free-electron like surface state, the electronic structure of Be(10-10) consists of two electron pockets at the boundary of the surface Brillouin zone which leads to strongly anisotropic screening. In this talk measurements of the electronic, geometric and vibrational structure of Be(10-10) are presented. The results are compared to recent first-principles calculations [1] and discussed in the context of other simple metal surfaces. An attempt is made to establish a connection between the remarkable surface electronic structure and the other properties. [1] R. Stumpf, private communication.