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Title: Ge/SiGe-based thermoelectric generator
Author: Odia, Ameze
ISNI:       0000 0004 6347 3454
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 2017
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This thesis summarizes the milestones achieved in building a thermoelectric generator (TEG) device using a novel p- and n- type 2-D thermoelectric material called Ge/SiGe superlattice; which was grown by low energy plasma- enhanced chemical vapour deposition (LEPECVD). It begins by describing in a nutshell the advances made in the area of thermoelectrics since its inception in 1821, to the present application of nanotechnology to develop state-of-the-art thermoelectric materials of which the aforementioned material is one. Next, characterisation of the Ge/SiGe superlattice using a combination of experiment and Finite Element (FE) modelling is explained and the results obtained are discussed in comparison with published experimental results. Thereafter, experimental and FE results of the application of the Ge/SiGe superlattice to fabricate a TEG device are presented and discussed. The experimental results on the fabrication of Ge/SiGe TEG device is the first major success at achieving practically feasible voltage output of up to 2.16 mV. For ease of comparison with other published work, an effective Seebeck coefficient of 471.9V/K was estimated. At impedance matched loads of 15  and temperature difference measured across the device of 5.6 K, a power density of 0.111 W/cm2 and thermal efficiency factor of 0.0035 Wcm-2 K-2 were also estimated. The results though comparable to a few published works, still required further improvements. The limitations of the TEG that resulted to the low aforementioned performances were discussed; some of which include the restriction of the TEG to a unicouple, having only one p- and n-leg. This limitation is related to the development of the p-type Ge/SiGe material which was identified during the course of this research work. Another major limitation is that the improvised design of the unicoupled TEG, makes use of indium bonding to connect the p- and n- legs electrically in series and thermally in parallel. Indium has a low melting temperature of about 120ºC. Hence increasing the heat source above this temperature will dislocate the legs. The consequence of this is that the attainment of a significant temperature difference across the TEG that will eventually result to a high Seebeck voltage, based on the Seebeck effect principle, is limited. Ways to address these problems were therefore discussed as recommendations for future research work.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TK Electrical engineering. Electronics Nuclear engineering