Refrigeration by combined tunneling and thermionic emission in vacuum: Use of nanometer scale design

We consider new possibilities for cooling by vacuum tunneling. We examine a nanogeometry and find that large cooling currents can be obtained by a combination of energy selective tunneling of electrons and thermionic emission. The energy selective tunneling is a result of the special form of a potential barrier which has wider gap for low energy electrons, which results in electrons above the Fermi level being the principal tunneling component. Numerical calculations show that available material with work functions about 1.0 eV are useful for cooling. For gaps of 5-15 nm, which are well within the present state of the art, only a small external voltage (1-3 V) is required to create large currents and a useful Peltier coefficient of about 0.3, and cooling power of 100 W/cm(2). (C) 2001 American Institute of Physics.