Comparative STM and RHEED studies of Ge/Si(001) and Si/Ge/Si(001) surfaces

Although epitaxial growth has been traditionally monitored by reciprocal space techniques, such as reflection highenergy electron diffraction (RHEED), the development of surface-sensitive imaging techniques, such as scanning tunneling microscopy (STM), allows for monitoring in the real-space. RHEED averages information over relatively large sample regions, and is thus more representative of the dominant surface morphology, which, however, makes it less sensitive than STM to the presence of small amounts of scatterers, or to local surface modifications. Compressively strained Ge/Si(001) surfaces exhibit a rich variety of twoand three-dimensional structures, which are interesting from a phenomenological standpoint, and may have far-reaching implications for the semiconductor industry. A comparison between these two techniques in the specific case of a Ge–Si heterosystem emphasizes how the complementary information provided by RHEED and STM is essential for a correct interpretation of the data. © 1999 Elsevier Science B.V. All rights reserved.