Enhanced energy filtering and thermopower from synergetic scatterings of electrons at interface potential barriers (or wells) in semiconductor-based nanocomposites dispersed with metallic particles

The electron scattering by the mesoscopic interface potentials in semiconductor-based thermoelectric nanocomposites dispersed with spherical metallic nanoparticles was theoretically investigated. The scattering probabilities were analytically calculated by using perturbation theory, and scattering parameter lambda was determined through the energy dependence of relaxation time tau = tau E-0(lambda-1/2) (here, E is the energy). The results indicate that single scattering of electrons by either the interface potential barriers or wells formed due to the nanoparticles embedded in semiconductors cannot yield a magnitude of lambda larger than 2.4. In contrast, a magnitude of lambda as large as 3.4-4.9 can be achieved if synergetic scattering of electrons at ionized impurities and the potential barriers or wells occurs. In addition, on the whole, the scattering parameter for synergetic scattering is a weak function of temperature in the temperature range (100 K-850 K) investigated, and the magnitude of lambda is influenced to a degree by adoption of different energy dispersion relations. Based on the obtained lambda values, thermopower was calculated, which shows that thermopower of the nanocomposites was enhanced considerably for synergetic scattering as compared to single scattering, indicating that the synergetic scattering is an effective mechanism that strengthens energy filtering and enhances thermopower in nanocomposites. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3669447]