Phonon-blocking electron-transmitting structures

We present the concept of phonon-blocking electron-transmitting structures, desirable for high-performance thermoelectric devices, with the measured properties of p-type Bi/sub 2/Te/sub 3//Sb/sub 2/Te/sub 3/ superlattice materials. Transmission electron microscopy data indicate that these superlattices are structurally nearly ideal; this is also supported by the in-plane carrier transport measurements which suggest that superlattices offer higher mobilities compared to alloy films. The cross-plane carrier transport has been evaluated by a transmission line model technique, adapted to measure the electrical conductivities normal to the plane of the thin films. From a phonon-transport point of view, the superlattices offer significantly reduced lattice thermal conductivities compared to that of alloys. Prototypal thermoelements have been prepared with these superlattice films and other reference materials. Peltier-effect differential temperatures in the range of 2 to 4K are inferred across the thermoelements during quasi-steady state current flow. Figure of merit (ZT), from isothermal cross-plane electrical resistivities and adiabatic Peltier voltages, in bulk, thin-film alloys, and superlattice thermoelements were /spl sim/1, /spl sim/0.4, and 1.6 to 3, respectively.