End States in One-Dimensional Atom Chains

Jason N. Crain, Daniel T. Pierce

A new kind of state is observed at the boundaries of one-dimensional atom chains via scanning tunneling microscopy.  Such “end states” can be thought of as zero-dimensional analogs to two-dimensional states that occur at the surfaces of three-dimensional crystals. 

To fabricate chains we take advantage of the self-assembly of gold on the vicinal Si(553) surface. This approach produces parallel arrays of metallic chains that cover macroscopic sample areas [1]. Scanning tunneling microscopy images taken at positive and negative polarities reveal contrast reversal at the end atoms.  Spatially resolved scanning tunneling spectroscopy is used to map the density of states along the chains revealing a transfer from the empty to the filled states over the end atoms. 

The formation of end states leads to a breakdown in the simple particle in a box model for quantized states in finite chains.  A comparison to a tight-binding model demonstrates how the formation of end states transforms the density of states and the quantized levels within the chains.  Calculated STM topography profiles at positive and negative biases reproduce the experimentally observed end-atom contrast [2].

[1] J. N. Crain, A. Kirakosian, K. N. Altmann, C. Bromberger, S. C. Erwin, J. L. McChesney, J.-L. Lin, and F. J. Himpsel, PRL 90, 176805 (2003).

[2] J. N. Crain and D. T. Pierce, scheduled for publication in Science in February.

Presenting Author’s Information

Name: Jason N. Crain

Mentor: Daniel T. Pierce

Division: 841

Laboratory: Physics

Room: A241

Building address: Building 216

Mail Stop: 8412

Telephone: 3744

FAX #: (301)-926-2746

Email:Jason.crain@nist.gov

Sigma Xi member: no

Category: Physics