The synthesis of novel functional crystalline films on semiconductor substrates calls for atomic-level knowledge and controlling of the initial stages of interface or junction formation. Technologically relevant epitaxial oxide films can be grown on Si(100) surfaces modified by submonolayer alkaline earth adsorbates, e.g., barium (Ba) and strontium (Sr). Nevertheless, the fundamental properties of such surfaces, that is, Ba/Si(100) and Sr/Si(100) reconstructions are still controversial, which hinders a deeper insight into the synthesis of crystalline oxide films on silicon. In this study, scanning tunneling microscopy (STM), low-energy electron diffraction, synchrotron-radiation photoemission, and ab initio calculations have been utilized to examine Sr- and Ba-induced Si(100)(2 x 3) reconstructions that form the first mediating step in the growth of various functional oxide films on Si(100). The presented results elucidate the atomic and electronic structures of the Si(100)(2 x 3)-Sr and -Ba interfaces, giving support to the so-called (2 x 3) dimer vacancy structure. In particular, using STM, we demonstrate an evidence for the Si dimer, one of the main structural elements of metal-induced reconstructions on semiconductor (100) surfaces. It is also shown that in contrast to the dimer vacancy geometry, the other models, proposed for the Sr- and Ba/Si(100)(2 x 3) earlier, cannot be adopted.
2014. Vol. 118, no 4, 1894-1902 p.