Recent developments in nanostructured thermoelectric materials and devices

Thermal management is a critical issue for microelectronic and microphotonic devices. The efficiency of actual thermoelectric devices is determined by the thermoelectric figure of merit Z. Because Z has unit of inverse temperature, nondimensional figure-of-merit ZT that appears often in device analysis is commonly used. The best ZT materials are found in heavily doped semiconductors which has ZT /spl sim/ 1. One particularly fruitful and exciting approach has been the use of nanostructures. In this paper, the low-dimensional structures can be considered as new materials, despite the fact that they are made of the same atomic structures as their parent materials. Because the constituent parent materials of low-dimensional structures are typically simple materials with well-known properties, the low-dimensional structures are amenable to a certain degree of analysis, prediction and optimization. The state-of-the-art of thermoelectric materials research is described here. In thermoelectric devices it is the electrons that do the useful energy conversion work and the electron temperature that matters for energy conversion. If there is a way to impart energy to electrons while minimizing the coupling to phonons, it is possible to decouple the electrons and phonons. The schematic diagram of surface plasmon coupled nonequilibrium thermoelectric cooler, which uses surface plasmons to transfer energy preferentially to electrons and utilizes non-equilibrium electron-phonon effect in thermoelectric device is shown.