Bright edges of potassium islands on graphite are caused by the measurement

15.04.2009

Researchers at the Nanoscience Center (NSC) of the University of Jyväskylä, together with researchers from the University of Birmingham, have shown that scanning tunneling microscopy (STM) measurements of nanoscale phenomena can be affected by the measurement device.

The research group at the University of Birmingham experimentally observed monolayer-thick islands of potassium atoms on graphite substrate. Using STM imaging they discovered that the edges of the potassium islands shone brightly.

Using ab initio density functional calculations and STM simulations, the NSC researchers at the University of Jyväskylä showed that the results are affected by the potential difference between the measuring probe and the target, and that the bright edges are caused by the electric field of the device itself.

Hence, measuring in the quantum world may change the measuring object, and this should be taken into account in future STM imaging. "The dependence on potential in STM imaging is also an important finding for theorists, because the electric field is commonly ignored in STM simulations", says Jaakko Akola (University of Jyväskylä, Nanoscience Center and Tampere University of Technology, Department of Physics).

The research group used CSC's computing resources and the GPAW software developed by CSC, Helsinki University of Technology, Tampere University of Technology, the University of Jyväskylä, and the Technical University of Denmark. The results were published in Physical Review Letters, a highly regarded scientific journal, where the article received a special marking as "Editors' Suggestion".

Read more

F. Yin, J. Akola,  P. Koskinen, M. Manninen, and R. E. Palmer1: Bright Beaches of Nanoscale Potassium Islands on Graphite in STM Imaging. 13.3.2009

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