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• Nanomagnetics
• Atomic scale characterization & fabrication
• Modeling nanostructures in mesoscopic environments
• Nanoscale measurement & fabrication using laser-controlled atoms
• Atom Optics
• Magneto-Optic Microscopy
• Magnetic Force Microscopy
• Nanoscale Physics
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• UHV STM

Spectroscopy of Quantized States in Finite Atomic Chains

In recent years, one-dimensional systems have been found to exhibit surprising electronic properties that are different than in three dimensional systems. To study electronic states in one-dimension, we fabricate atomic chains by depositing gold on stepped silicon surfaces. The energetics of the stepped surfaces drives the formation of atomic chains that cover the entire surface. Perfect chains can be up to 70 atoms in length.

Figure 1
Figure 1. 10 nm × 60 nm STM topography image of self assembled atom chains on the Si(553) surface.

The finite length of the chains plays a crucial role in determining their electronic structure. By mapping the density of states along finite chains using scanning tunneling spectroscopy (STS), we find the formation of quantized states within finite chains and localized states at the end atoms. In the limit of infinite chains, these "end states" can be thought of as the zero-dimensional analogs to two-dimensional states that occur at a bulk surface.


Figure 2
Figure 2. 8 nm × 19 nm STM topography images of the same sample area at positive (top left) and negative (bottom left) biases reveal a contrast reversal over the end atoms. A tight binding model shows the density of states along a four-atom chain (right) with atomic position along the horizontal direction and energy along the vertical direction. Red shows regions of high density of states. At +0.5eV the density of states is localized over the center two atoms while at -0.7eV localized states are found over the end atoms. The missing density of states over the end atoms at positive energies accounts for the observed change in contrast on the end atoms seen in the STM on reversing the sample bias and is due to the formation of "end states".


Related Publications listings
End States in One-Dimensional Atom Chains

Staff listings
Daniel T. Pierce

Former Staff listings
Jason Crain

Online: April 2005
Last Updated: February 2008

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