Surface structure determination with X-ray standing waves

The SiC(0001)6√3 × 6√3 reconstruction studied with STM and LEED

SUMMARY

We have used scanning tunnelling microscopy (STM) to study changes in the structure of the Si(111) surface induced by deposition of the group III metals In and Ga. For both metals, several different ordered reconstructions are seen as a function of coverage. The STM images provide new structural information on each of these reconstructions. With In metal deposition, we have seen the surface reconstructions √3×, √3, √31× √31, √7×√3 and 4×1 as the coverage increases. In the case of Ga on Si(111), we have studied structures that exist up to 0·7 ML. At 1/3 ML, there is a √3×√3 structure identical to that of In. Above 0·3 ML there is a different phase that may correspond to the (6·3times6·3) RHEED pattern reported in this coverage range. This surface tends to grow as triangular islands at higher coverages.

Metal-induced reconstructions of the silicon(111) surface

The present work is devoted to the application of STM to the study of the initial stages of film growth. The aim of such measurements is to learn more on the atomic processes during the overlayer deposition. So far, most results in this field have been obtained on metalkemiconductor systems. Under optimum resolution the adsorption sites in the low-coverage regime can be observed directly. For larger coverages the metal deposit very often condenses in form of three-dimensional islands, whose shape and size distribution may be determined. To understand the content of the STM images more clearly, theoretical concepts of STM are summarized. Experimental details are also given. The possibility of spectroscopic imaging with STM gives access to electronic effects during nucleation and film growth.

STM studies of nucleation and the initial stages of film growth

SUMMARY

The scanning tunnelling microscope (STM) has proved to be an extraordinary method to investigate surfaces in vacuum, air and liquid environments. Several issues regarding the use of the STM for atomic resolution studies are discussed. These include electronic contributions to STM images, the role of the tip in resolution and spectroscopy, as well as the need for complementary information about chemical composition or sub-surface structure.

Salvan F

Papers

Examination of the Cu/Si(111) 5×5 structure by scanning tunneling microscopy