OBSERVATION OF SURFACE RECONSTRUCTION ON SILICON ABOVE 800-DEGREES-C USING THE STM

AN understanding of the kinetics of structural phase transitions in crystalline, semiconducting thin films is important for the control of film growth in techniques such as molecular-beam epitaxy, as well as in applications of such films at high temperatures. Electron diffraction techniques (LEED and RHEED) have been applied to the study of high-temperature surface reconstruction, but although these can detect changes in surface periodicity, they do not permit atomic-scale resolution of the nucleation and growth processes. The scanning tunnelling microscope (STM) provides an alternative tool to investigate changes of this sort, but high-temperature observations have been hampered by problems of thermal drift. Here we report our success in overcoming these problems and thus in obtaining atomic-resolution STM images of the 1 x 1 --> 7 x 7 surface reconstruction of a silicon thin film at about 860-degrees-C. Step formation and migration are clearly visible in these images.