ICT2014 Abstracts

Thermoelectric generator devices are of interest in waste heat recovery and as primary heat-to-electricity sources. One concept of interest to achieve high energy conversion efficiency is a thin film superlattice, where the n-type or p-type legs are composed of 1000s of nanometer-scale thick layers. Superlattice systems, such as the n-type silicon/silicon-carbide films described here, aim to take advantage of quantum-scale effects, increasing both Seebeck coefficient and electrical conductivity, and decreasing thermal conductivity, in comparison to bulk form values. Film morphology and fabrication are important factors in determining the figure of merit of the material. Si/SiC superlattices were deposited onto several candidate substrate materials using ion beam sputter deposition with varying substrate temperature and layer thickness. Si/SiC n-type films have been previously grown on intrinsic silicon substrates. Substrates with low thermal and electrical conductance as well as geometric complexity are needed for real-world devices, and specific ideal substrates must match coefficients of thermal expansion to the film. The substrate-film interface is also important to achieve well adhered films. It  has been shown that the temperature of deposition has a direct effect on the thermoelectric properties. Two components of the figure of merit, the Seebeck coefficient and electrical resistivity, are measured and used to compare film performance among samples. Mobility, carrier density, and activation energy are measured to characterize the film quality. Finally, film morphology is evaluated with atomic force microscopy and scanning white light interferometry.