IN SITU STM STUDY OF THE GE ON SI MOLECULAR BEAM EPITAXY. Bert Voigtlander, Institut fur Grenzflächenforschung und Vakuumphysik Forschungszentrum Jülich, 52425 Jülich, Germany

A high temperature scanning tunneling microscope (STM) capable of imaging during MBE-growth is described. We studied the epitaxial growth of Germanium on Silicon at 600 - 900 K sample temperature "in vivo". This technique gives access to the dynamics of the growth process on an atomic scale. The potential of the method is demonstrated by the following results:

The layer-by-layer growth of the two-dimensional Stranski-Krastanov layer of Ge on Si(111) and the formation of three-dimensional islands during further growth of Ge was observed. An inversion of the aspect ratio of the islands with increasing coverage indicates a transition from coherent to dislocated islands.

The transition from initial multilayer to pure layer-by-layer growth was imaged in Si(111) homoepitaxy.

In Si(111) homoepitaxy growth was observed along stripes of the width of a (7x7) unit cell. Upon coalescence of islands new growth facets with different growth speeds are observed.

Some of the results will be presented on videotape. This method (MBSTM) opens the possibility to follow MBE growth processes dynamically on a nanometer scale and gives access to the evolution of specific features during growth.