Dresden 2014 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 49: Energy materials: Thermoelectrics

HL 49.4: Vortrag

Dienstag, 1. April 2014, 14:45–15:00, POT 051

Phononic thermal transport in nanostructured silicon membranes — •Sanghamitra Neogi, Luiz F. C. Pereira, and Davide Donadio — Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany

The interest in energy harvesting using thermoelectric devices and thermal management in nanostructures has heightened the necessity of understanding the phononic thermal transport in nanoscale materials. Nanostructuring can result in the reduction of the thermal conductivity of crystalline semiconductors while preserving their electronic properties, leading to an improved TE efficiency in these systems [1].

We use harmonic lattice dynamics and classical molecular dynamics to investigate the nature of phononic thermal transport in ultra-thin silicon membranes, with thicknesses up to 20 nm. We show that dimensionality reduction has a significant effect on the phonons of the membranes and leads to a 4-fold reduction in the thermal conductivity of the membranes. Nanostructuring Si membranes by means of pattern formation and surface oxidation, in combination with dimensionality reduction, results in a 25-fold reduction in the thermal conductivity of the membranes with respect to the bulk, implying a 25-fold enhancement of the thermoelectric figure of merit at room temperature. Such figures make nanostructured silicon membranes viable materials for thermoelectric units.

[1] M. S. Dresselhaus et al, Adv. Mater., 22, 3970 (2010).

Acknowledgment: This project is funded by the program FP7-ENERGY-2012-1-2STAGE under contract number 309150.