Atomic and Electronic Structure of Clusters on Silicon Surfaces
Final Report Abstract
In this project, the growth, atomic structure and local electronic properties of selected cluster structures on silicon surfaces were investigated using scanning tunneling microscopy (STM) and spectroscopy (STS). It turned out that the Si(111)7x7 surface is an ideal template for the formation of a variety of cluster structures, since the 7x7 periodicity and most of the silicon surface remain intact upon cluster formation. For the case of antimony deposition on Si(111)7x7, the formation of ringlike clusters was observed and their atomic structure was determined. These clusters are characterized by different apparent heights in the STM images, indicating a substitutional replacement of different numbers of silicon atoms by antimony atoms, while the fundamental atomic structure remains unaffected. This behavior, which may be considered antimony doping, also leads to corresponding shifts of the Fermi level position within the clusters, as revealed by STS. Rare earth deposition on Si(111)7x7 leads to two different cluster types, one positioned centrally within the Si(111)7x7 half unit cell and one positioned off-center, and the structure of both types could be determined from the STM data. For the centered rare earth clusters, a switching between two mirror-symmetric configurations was found in the case of a closely approached tunneling tip, which is attributed to a tip-induced lowering of the energy barrier between the two configurations. Hence these clusters are an interesting model system for atomic-scale nanomemories with extremely high area densities that may be operated even at room temperature. A detailed STS investigation of indium clusters on Si(111)7x7 demonstrated semiconducting properties with an energy gap depending on the cluster position on the surface as well as on the presence of neighboring clusters, indicating a considerable electronic cluster-cluster interaction as well as a strong influence of the neighboring quasi-metallic Si(111)7x7 surface. On the Si(557) surface, which is vicinal to Si(111), these indium clusters were found to assemble in one-dimensional cluster chains.
Publications
- Antimony induced cluster formation on the Si(111)7x7 surface, Surf. Sci. 608, 109 (2013)
S. Appelfeller, M. Franz, and M. Dähne
(See online at https://doi.org/10.1016/j.susc.2012.09.021) - Formation and atomic structure of self-assembled Dy silicide clusters on the Si(111)-7x7 surface, Surf. Sci. 609, 215 (2013)
M. Franz, S. Appelfeller, M. Rychetsky, and M. Dähne
(See online at https://doi.org/10.1016/j.susc.2012.12.010) - Atomic structure and electronic properties of self-assembled clusters on silicon surfaces, PhD Thesis, Technische Universität Berlin 2015
M. Franz
(See online at https://doi.org/10.14279/depositonce-5007) - Terbium induced nanostructures on Si(111), Surf. Sci. 637-638, 149 (2015)
M. Franz, J. Große, R. Kohlhaas, and M. Dähne
(See online at https://doi.org/10.1016/j.susc.2015.03.026) - Capping of rare earth silicide nanowires on Si(001), Appl. Phys. Lett. 108, 013109 (2016)
S. Appelfeller, M. Franz, M. Kubicki, P. Reiß, T. Niermann, M.A. Schubert, M. Lehmann, and M. Dähne
(See online at https://doi.org/10.1063/1.4939693) - Modification of the electronic properties of magic In clusters on Si(111)7x7 by different environments, J. Vac. Sci. Technol. B 34, 04J101 (2016)
M. Franz, J. Schmermbeck, and M. Dähne
(See online at https://doi.org/10.1116/1.4947265)
