Semiconductor Nanowire and Nanoribbon Thermoelectrics: A Comprehensive Computational Study
Technical Report,15 Mar 2009,14 Mar 2012
University of Wisconsin - Madison Madison United States
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Through detailed microscopic simulation, this project advances our understanding of the transport of charge and heat in Si, SiGe, and graphene nanostructures, with the objective of furthering their applications in thermoelectric cooling and energy harvesting. Main findings include 1 Room-temperature thermoelectric figure of merit, ZT, of ultrathin silicon nanowires varies slowly with thickness, having a soft maximum of about 0.4 at the nanowire thickness of 4 nm. The benefit of nanostructuring is much less dramatic than previously suggested 2 We find a significantly enhanced thermoelectric power factor in gated Si nanomembanes, and explain that it occurs due to include quantum confinement, low scattering due to the absence of dopants, and, at low temperatures, a significant phonon-drag contribution 3 In Si nanomembranes, in-plane thermal conductivity is minimal on 001, due to the strong coupling of TA modes to 001 surfaces. Highest in-plane conductivity is achieved in 100011 SOI, with benefits for passive cooling applications. 4 Thermal transport in suspended graphene nanoribbons is edge-dominated and highly anisotropic, but isotropic in realistic-sized supported nanoribbons owing to strong substrate scattering.