Controlling the electronic surface properties of a material

July 17, 2009
A two-dimensional “electronic metamaterial” is generated by supramolecular selfassembly on a metal surface. The periodic influence of the porous molecular network on the otherwise free-electron-like surface state results in the formation of an electronic band.

A recent breakthrough by researchers at the Swiss Nanoscience Institute sees for the first time the creation of thin films with controllable electronic properties. This discovery could have a large impact on future applications in sensors and computing. The international collaboration of researchers from the Universities of Basel and Heidelberg and the Paul Scherrer Institute (Switzerland) have published the work in the prestigious scientific journal Science.

It's commonly accepted that electrical resistance of a given material cannot be adjusted as is the case with, for example, density and color. However, Dr Meike Stöhr and her collaborators have now succeeded in developing a new method to selectively tune surface properties such as resistance.

The interdisciplinary team of physicists and chemists have developed a substance which, after heating on a surface, exhibits a two dimensional network with nanometer sized pores. The interaction of this network with the existing electron gas on the metal surface leads to the following effect: the electrons underneath the network are pushed into the pores to form small bunches of electrons called .

By varying parameters such as the height and diameter of the pores the possibility arises to selectively tune the properties of the material. Further possibilities arise from the ability to fill the pores with different molecules. This allows direct access to the properties of the material which are dependent on the electronic structure, such as conductivity, reflectivity and surface catalysis properties. This will lead to the emergence of new materials with adjustable .

The underlying physical mechanisms can best be understood by a comparison of the electron-gas with waves in water. Waves on a water surface are reflected by any obstacle they meet. If the obstacle on the surface in question resembles a honeycomb structure, standing waves are set up in each cell of the honeycomb. This then leads to a wave pattern representative of the honeycomb structure of the same size and shape. “Applying this analogy to the electron gas, we see that the interaction of the network structure with the electron gas on the metal surface confines the electrons giving rise to a characteristic electron wave structure of the new material.” says Stöhr.

These pore networks are good candidates for new meta-materials. These are man-made materials which, due to their period architecture, have specific optical and electronic properties not found in nature. These properties can be tuned by changing the properties of their component materials. In the case of pore networks, it is the electronic surface properties which can be tuned by careful selection of the nano-pores.

Source: Paul Scherrer Institut

Explore further: A mysterious change in the wave properties of electrons

Related Stories

A mysterious change in the wave properties of electrons

September 30, 2004

The electrons of a perfect metallic surface move like free waves in a plane. Nevertheless, if atomic barriers are inserted, this may restrict their movement in one dimension, forming stationary waves such as those on the ...

Experiments Prove Existence of Atomic Chain Anchors

February 3, 2005

Atoms at the ends of self-assembled atomic chains act like anchors with lower energy levels than the “links” in the chain, according to new measurements by physicists at the National Institute of Standards and Technology ...

Innovation in Nanoporous Chemistry

September 30, 2005

Science researchers from the University of Versailles (France), in collaboration with the ID31 beam line at the European Synchrotron Radiation Facility (ESRF), report their progress in the design and characterisation of microporous ...

Physicists discover surprising variation in superconductors

January 28, 2009

( -- MIT physicists have discovered that several high-temperature superconductors display patchwork quilt-like variations at the atomic scale, a surprising finding that could help scientists understand a new class ...

Recommended for you

Physicists develop new technique to fathom 'smart' materials

November 26, 2015

Physicists from the FOM Foundation and Leiden University have found a way to better understand the properties of manmade 'smart' materials. Their method reveals how stacked layers in such a material work together to bring ...

Mathematicians identify limits to heat flow at the nanoscale

November 24, 2015

How much heat can two bodies exchange without touching? For over a century, scientists have been able to answer this question for virtually any pair of objects in the macroscopic world, from the rate at which a campfire can ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.