CPM Seminar

Measuring Electronic Effects in Reduced Dimensions:
Scanning Tunneling Microscopy of Atomic Chains and Sheets

Jason Crain

National Institute of Standards and Technology

As the size of nanostructures approach the atomic scale, boundaries and defects play an increasingly crucial role in the electronic structure. Scanning tunneling microscopy (STM) provides a unique tool to investigate these electronic effects with atomic resolution. In this talk I will present recent work investigating the electronic structure for model systems at the one- and two- dimensional limits via STM. One-dimensional chains of atoms are self-assembled by depositing gold on stepped silicon surfaces. We find that individual defects effectively break the chains into isolated segments leading to quantum size effects. These size effects are manifest in both localized resonances observed in individual segments [1] and preferred lengths observed in the distribution of segments [2]. To achieve two-dimensional sheets, silicon is thermally evaporated from a SiC surface to form ultra-thin graphite films. We investigate the interfacial electronic structure that forms between the SiC and the first layer of graphite. For few layer films electron interference patterns are observed that display both atomic scale and nanometer scale fluctuations, due to the unique band structure of the graphite.

[1] J.N. Crain and D.T. Pierce, Science 307, 703 (2005).
[2] J.N. Crain, M.D. Stiles, J.A. Stroscio, and D.T. Pierce, PRL 96, 156801 (2006).