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An investigation of properties of nanoscale metallic structures on silicon is in the center of interest of surface physicists. However, utilization of such structures for production of nanodevices requires deep understanding of their local electronic structure which is intimately related to their geometry and also reflects the interaction between metal atoms and the silicon surface.
Here we present a study of local density of states of indium chains formed on the Si(100)-(2x1) surface studied by spatially resolved scanning tunneling spectroscopy. Indium deposited on Si(100)-(2x1) surface forms atomic chains perpendicular to the dimer rows of the reconstruction. It has been already shown, that the growth is strongly influenced by the so called C-type defects (formed by disociated water molecule). They act as nucleation centre and represent a stable termination of the indium chains during further growth. Tunnel spectra were measured at significant positions of (2x1) reconstruction, at dimer rows of the reconstruction above and between silicon dimers, and between dimer rows. In every experiment we measured spectra of the clean silicon surface together with spectra at positions of C-type defects and on different parts of indium chains, especially on the chain end pinned to the C-type defect. Well known tunnel spectra of the clean Si(100)-(2x1) surface were used as reference to assure reliable and reproducible measurement. We will discuss an influence of the adsorbed indium atoms on the surface electronic structure of the clean Si surface as well as on electronic properties of the C-type defects.
We use a non-commercial ultra high-vacuum STM system with DSP based control electronic (TORO-16 card from Innovative Integration). dI/dV-V curves are taken directly during the scanning at choosen positions of the surface using lock-in technique. This together with the real time compensation of lateral drifts allows precise determination of positions, where the spectra are measured, even at room temperature. |