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New Approach for the Synthesis of IV-VI Thermoelectric Thin Film Materials and Devices on Si: (211) PbSnSeTe/ZnTe/Si Heterostructures
Published online by Cambridge University Press: 01 February 2011
Abstract
Low-dimensional thin-film thermoelectric materials including superlattices and quantum-dot heterostructures have shown significant potential for improving the thermoelectric properties. Highly structured thin film materials such as these would be useful for integrated microdevices such as power MEMS and thermally triggered MEMS actuators. For reasons including scalability and ease-of-integration, silicon is the choice material for the substrate, however there is a lattice and a thermal-expansion mismatch. In this work, a new approach for the synthesis of integrated PbSnSeTe based thermoelectric thin film materials on silicon is demonstrated by employing an epitaxial buffer layer of II-VI compound telluride materials (e.g., ZnTe, CdTe) to help bridge the lattice and thermal expansion mismatches with silicon. This multilayer can be used for subsequent growth of thick films having low-dimensionality structures. We report the initial results from studying the structural and thermoelectric properties of simple solid-solution alloy PbSnSeTe thin films on ZnTe/Si heterostructures. Data from transmission electron microscopy and in-situ electron diffraction will be presented that shows that despite the large lattice mismatch with silicon and the three different crystal structures, unusually high structural quality PbSnSeTe has been obtained by matching the (211) lattice symmetry and the lattice spacing along the [110] directions of the ZnTe and PbSnSeTe. The structural quality of the PbSnSeTe was studied by measuring the dislocation density through etch-pit counting and x-ray diffraction. Results presented will show that a dislocation density as low as 1.2 × 106/cm2 can be achieved by strategic lattice-matching between the buffer and thermoelectric layers. Electrical resistivity, doping density, and Seebeck coefficient values for solid-solution alloys without low-dimensional structuring will be shown to approach those of high-performance bulk.
Keywords
- Type
- Research Article
- Information
- MRS Online Proceedings Library (OPL) , Volume 1044: Symposium U – Thermoelectric Power Generation , 2007 , 1044-U09-07
- Copyright
- Copyright © Materials Research Society 2008