STTR Phase I: Materials for Sustainability

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This Small Business Technology Transfer Phase I project will evaluate a novel approach to fabricate high efficiency quantum well thermoelectric films on low thermal conductivity, affordable substrates. Hi-Z Technology has made significant advances in developing thermoelectric thin film materials based on Quantum Well (QW) to achieve high figure of merit using single crystal silicon substrate, but the higher thermal conductivity of the substrate greatly increases the heat losses and reduces overall efficiency, so lower thermal conductivity and low-cost QW thermoelectrics have not been possible on these substrates. This innovation is to create single crystalline-like films of silicon atop Kapton and glass substrates so as provide a surface similar to single crystal silicon wafer for growth of QW thermoelectrics. The enabling method to achieve single crystalline-like silicon films is a template synthesized by ion beam assisted deposition which is expected to provide biaxial texture of crystals even on Kapton and glass substrates. The anticipated result is QW thermoelectric films on low thermal conductivity, affordable substrates with figure of merit comparable with that achieved on single crystal Si substrates. A successful implementation of this innovation would lead to highly efficient, commercially feasible systems for both power generation and large-scale cooling application which are the markets that Hi-Z technology is addressing in its business. Power generation from waste heat recovery by thermoelectric materials can greatly improve the efficiency of use of fossil fuels especially in automobiles. Thermoelectric materials can enhance efficiency of photovoltaic energy generation by converting otherwise wasted heat into power. Thermoelectric materials provide multifunctionality in that they could also be used in cooling applications and replace current mechanical vapor compression systems. In addition to commercial potential, a strong understanding of the mechanisms of biaxailly-textured crystalline growth by ion beam assisted deposition on polymer and glass substrates is expected to be gained from work. Additionally, investigation of epitaxy of silicon on lattice mismatched template layers would lead to a broad impact beyond this project. Furthermore, this project is anticipated to shed light on mechanisms of intricate interplay among electrical and thermal parameters governing thermoelectric thin film properties. Students and post-doc working at the University of Houston, subcontractor to this project, will benefit from research and education experience on thin film growth mechanisms, texture, epitaxy, and thermoelectrics properties.