Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 97: Nanostructure at Surfaces: Structures and Properties

O 97.2: Vortrag

Freitag, 20. März 2015, 10:45–11:00, MA 005

novel structures and phenomena in ultrathin films — •rajib batabyal and bhupendra nath dev — indian association for the cultivation of science, kolkata, india

Nanostructures and thin films on well-defined substrate surfaces, their stability and exploration of new physical phenomena are important aspects not only for the development of future nanoscale devices but also for the advancement of basic physics research.

Here we discuss two major aspects of Ag ultrathin films on Si(111)-7x7 surfaces. In the first section, we demonstrate a new phenomenon related to the electronic transport in 2-D to 3-D crossover. By STS measurement we show the dependence of the negative differential resistance (NDR) with film thickness for one-atomic layer to five-atomic layer thick films. The dependence of the onset voltage at which NDR sets in, is shown as a function of ultrathin film thickness. These results are explained via density functional theory (DFT) calculations. In the other section, we report on a novel mechanism in electric filed induced atomic migration and formation of one-atom thick fractal nanostructures. Application of a voltage pulse at an edge of a flat-top Ag island results in migration of Ag atoms from edge to the top of the island and aggregation to form a precisely one-atom thick fractal Ag layer. Diffusion limited aggregation (DLA) appears to be responsible for the formation of fractal nanostructures. We have also determined various fractal dimensions and corelated them to describe the morphology of fractal clusters.