About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
Publication
Physical Review B
Paper
Ultrafast-electron dynamics and recombination on the Ge(111)(2×1) -bonded surface
Abstract
Angle-resolved laser-photoemission spectroscopy has been used to study the ultrafast-electron scattering and recombination processes on the Ge(111) -bonded (2×1) surface with subpicosecond time resolution. Electrons photoexcited into the bulk Ge conduction band scatter into the unoccupied surface antibonding * band whose minimum is at the J» point in the surface Brillouin zone. Rapid relaxation to the surface-band minimum is followed by a unique phonon-assisted process in which electrons recombine with bulk holes at the valence-band maximum, which we find to be the primary mechanism responsible for the decay of the transient * population. Time-dependent measurements carried out at 300 and 120 K have been employed to determine the role of energetic phonons in the scattering processes. These processes are modeled with a set of rate equations, whose fits to the data yield scattering times used to determine a surface recombination velocity directly. Ultrafast surface-state hole dynamics are observed, and a renormalization of the surface band gap is studied as a function of electron density. The -bonded states are fundamentally one dimensional in nature, and thus these results represent studies of band-gap renormalization in a one-dimensional system. © 1992 The American Physical Society.