Ultra Thin Quantum Well Materials
This project has enabled Hi-Z technology Inc. (Hi-Z) to understand how to improve the thermoelectric properties of Si/SiGe Quantum Well Thermoelectric Materials. The research that was completed under this project has enabled Hi-Z Technology, Inc. (Hi-Z) to satisfy the project goal to understand how to improve thermoelectric conversion efficiency and reduce costs by fabricating ultra thin Si/SiGe quantum well (QW) materials and measuring their properties. In addition, Hi-Z gained critical new understanding on how thin film fabrication increases the silicon substrate's electrical conductivity, which is important new knowledge to develop critical material fabrication parameters. QW materials are constructed with alternate layers of an electrical conductor, SiGe and an electrical insulator, Si. Film thicknesses were varied, ranging from 2nm to 10nm where 10 nm was the original film thickness prior to this work. The optimum performance was determined at a Si and SiGe thickness of 4nm for an electrical current and heat flow parallel to the films, which was an important conclusion of this work. Essential new information was obtained on how the Si substrate electrical conductivity increases by up to an order of magnitude upon deposition of QW films. Test measurements and calculations are accurate and include both the quantum well and the substrate. The large increase in substrate electrical conductivity means that a larger portion of the electrical current passes through the substrate. The silicon substrate's increased electrical conductivity is due to inherent impurities and thermal donors which are activated during both molecular beam epitaxy and sputtering deposition of QW materials. Hi-Z's forward looking cost estimations based on future high performance QW modules, in which the best Seebeck coefficient and electrical resistivity are taken from separate samples predict that the electricity cost produced with a QW module could be achieved at <$0.35/W. This price would open many markets for waste heat recovery applications. By installing Hi-Z's materials in applications in which electricity could be produced from waste heat sources could result in significant energy savings as well as emissions reductions. For example, if QW thermoelectric generators could be introduced commercially in 2015, and assuming they could also capture an additional 0.1%/year of the available waste heat from the aluminum, steel, and iron industries, then by 2020, their use would lead to a 2.53 trillion Btu/year reduction in energy consumption. This translates to a $12.9 million/year energy savings, and 383.6 million lb's of CO2 emissions reduction per year. Additionally, Hi-Z would expect that the use of QW TE devices in the automotive, manufacturing, and energy generation industries would reduce the USA's petroleum and fossil fuel dependence, and thus significantly reduce emissions from CO2 and other polluting gasses such as NOx, SOx, and particulate matter (PM), etc.
- Research Organization:
- Hi-Z Technology, Inc.
- Sponsoring Organization:
- USDOE-Advanced Manufacturing Office; USDOE EE Office of Industrial Technologies (EE-2F)
- DOE Contract Number:
- EE0003492
- OSTI ID:
- 1047577
- Report Number(s):
- EE0003492; TRN: US201216%%687
- Country of Publication:
- United States
- Language:
- English
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QUANTUM WELL THERMOELECTRICS FOR CONVERTING WASTE HEAT TO ELECTRICITY
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Related Subjects
02 PETROLEUM
30 DIRECT ENERGY CONVERSION
ALUMINIUM
COST ESTIMATION
DEPOSITION
EFFICIENCY
ELECTRIC CONDUCTIVITY
ELECTRICAL INSULATORS
ELECTRICITY
ENERGY CONSUMPTION
FABRICATION
FOSSIL FUELS
HEAT FLUX
IMPURITIES
MOLECULAR BEAM EPITAXY
PARTICULATES
PETROLEUM
QUANTUM WELLS
SILICON
SUBSTRATES
THERMOELECTRIC CONVERSION
THERMOELECTRIC GENERATORS
THERMOELECTRIC MATERIALS
THERMOELECTRIC PROPERTIES
THIN FILMS
WASTE HEAT
NESDPS Office of Nuclear Energy Space and Defense Power Systems
Direct Conversion
Efficient
Quantum Well Thermoelectrics