Nov 16, 2007
Thermopower measurements on individual 30nm nickel nanowires
The miniaturization of electronic devices has now reached a point where even the metallic interconnects are approaching the length scale of their electron mean free path (a few tens of nanometers at room temperature), where strong deviation from bulk electrical properties takes place. If any predictions on these properties have to be made, the basic mechanisms contributing to the scattering of electrons in reduced dimensions must be known. However, the development of experimental approaches for this study is very challenging.
A new experimental approach was developed by researchers at Tel Aviv University. This was developed on the basis that the same size-dependent electron scattering mechanisms that affect the conductance of nanoscale metal structures should also affect their thermoelectric properties. Thus, by determining attributes such as the Seebeck coefficient of nanoscale materials, valuable insight into electron scattering processes can be gained. Additional information can also be obtained that is critical in the search for superior thermoelectric materials that are expected to very efficiently convert a temperature difference into electricity (Seebeck effect) and vice versa (Peltier effect).
As a specific example, the thermopower of individual, 30 nm diameter, Ni nanowires has been determined as a function of temperature. The role of boundary scattering of phonons on the Seebeck coefficient and electron scattering at grain boundaries on conductance were determined. Any future interpretation of size-dependent thermopower in nanoscale ferromagnetic materials will have to explicitly consider the observed effects from this study.
About the author
Yoram Selzer is a senior lecturer at the school of chemistry in Tel Aviv University, Israel. He is also associated with the center for nanoscience and nanotechnology at this university. His group is currently conducting research projects on molecular electronics and the development of novel methods to probe the thermophysical properties of materials on the molecular scale.