Dynamics of dimers and adatoms at silicon and germanium surfaces

Asymmetric dimers at the bare silicon (or germanium) (100) surfaces undergo a rapid flip-flop motion above an order-disorder phase transition temperature. We discuss, here, an intriguing controversial issue, namely the possibility of a kind of re-entrant dynamical behavior at very low temperatures. We further show that metal adatoms (typically, tin adatoms) adsorbed on the (111) surfaces behave also dynamically. The toolkit to address these questions is a synergetic combination of local probes and synchrotron radiation techniques. © 2007 Springer.