Aniketa Shinde

Morphological work function dependence of rare-earth disilicide metal nanostructures.

The work functions of various DySi(2-x) nanostructures epitaxially grown on a Si(001) surface were correlated with the structure using high-resolution Kelvin probe force microscopy and scanning tunneling microscopy in ultrahigh vacuum. Dy adatoms induce a surface dipole on Si(001) that increases the surface potential from 0.26 to 0.42 eV with respect to 2 x 1 reconstructed Si(001). DySi(2-x) nanowires showed a 0.2-0.23 eV lower work function than DySi(2-x) nanoislands, which can be attributed to confinement of electrons along the surface normal that induces a surface dipole when the film thickness approaches the Fermi wavelength. The ability to tune the work function of metal nanostructures should be useful for understanding how electronic structure affects catalytic activity.

Structural Understanding of Self-Assembled Rare Earth Disilicide Nanostructures Via Scanning Probe Microscopy and First Principles Studies

We performed systematic experimental and computational studies to investigate the adsorption geometries of Y atoms on the Si(001) surface. This paves a way for understanding and eventually controlling the growth of rare earth disilicide wires on the Si(001) substrate that are promising for various applications. For a single Y atom, the interrowdn site was found to be at least 400 meV lower in energy than other possible binding sites. The emulated STM images are in good agreement with experimental results of Er on Si(001). The strong bias and coverage dependence indicates the need for theoretical guidance for the correct interpretation of experimental data. We elucidate the Y-Si binding mechanism and provide insights toward the onset of formation of hexagonal rare earth disilicide wires.

Structural and Chemical Properties of Gold Rare Earth Disilicide Core−Shell Nanowires

Clear understanding of the relationship between electronic structure and chemical activity will aid in the rational design of nanocatalysts. Core-shell Au-coated dysprosium and yttrium disilicide nanowires provide a model atomic scale system to understand how charges that transfer across interfaces affect other electronic properties and in turn surface activities toward adsorbates. Scanning tunneling microscopy data demonstrate self-organized growth of Au-coated DySi₂ nanowires with a nanometer feature size on Si(001), and Kelvin probe force microscopy data measure a reduction of work function that is explained in terms of charge transfer. Density functional theory calculations predict the preferential adsorption site and segregation path of Au adatoms on Si(001) and YSi₂. The chemical properties of Au-YSi₂ nanowires are then discussed in light of charge density, density of states, and adsorption energy of CO molecules.