Interaction of Radiation with Surfaces and Electron Tunneling · Figs. 9 - 23

This chapter discusses scanning tunneling microscopy (STM) images of silicon (Si) and germanium (Ge) semiconductors. Surfaces are listed in order of increasing sum of Miller indices. This chapter illustrates i) STM image, tunneling spectroscopy results, high resolution images of silicon. Large-area STM image of Si(001) surface shows characteristic defect concentrations. These defects play important roles both because of the electronic energy spectrum and the effects they have on the nearby surface. The STM images show that in defect-free regions of the surface the dimmers appear to lie in the surface plane, while near defects and steps a tilting of the dimers can often be observed. On samples tilted by several degrees toward [110], the surface tends to adopt a single-domain structure, with terraces separated by double-height steps. Samples tilted at arbitrary angles show a mixture of single- and double-height steps. On scrupulously clean surfaces, it was found that only a "16 x 2" reconstruction is observed. The 2 x 1 reconstruction of Si(111) is readily produced by cleavage. STM images of the Si(111)7 x 7 surface reveal two triangular subunits. Each triangular subunit contains six protrusions at the locations of the "adatoms" of the DAS model. STM images of this surface show chain-like structures. STM images of Ge(001) show that the Ge(001) surface reconstructs by pairing of atoms to form dimers, in a manner similar to the Si(001) surface.