Germanium Nanostructures on Silicon Observed by Scanning Probe Microscopy

Scanning tunneling microscopy and noncontact atomic force microscopy have beenused to observe germanium growth on Si(001) and Si(111). The atomically resolvedimages provide invaluable information on heteroepitaxial film growth from the viewpointsof both industrial application and basic science.We briefly review the history ofcharacterizing heteroepitaxial elemental semiconductor systems by means of scanningprobe microscopy (SPM), where the Stranski-Krastanov growth mode can be observedon the atomic scale: the detailed phase transition from layer-by-layer growth tothree-dimensional cluster growth was elucidated by the use of SPM. In addition, wecomment on the potential of SPM for examining the spectroscopic aspects ofheteroepitaxial film growth, through the use of SPM tips with well-defined facets.