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Cating EE, Pinion CW, Van Goethem EM, et al. Imaging Spatial Variations in the Dissipation and Transport of Thermal Energy within Individual Silicon Nanowires Using Ultrafast Microscopy. Nano Lett. 2015;16(1):434-9doi: 10.1021/acs.nanolett.5b04075.
Cating, E. E., Pinion, C. W., Van Goethem, E. M., Gabriel, M. M., Cahoon, J. F., & Papanikolas, J. M. (2016). Imaging Spatial Variations in the Dissipation and Transport of Thermal Energy within Individual Silicon Nanowires Using Ultrafast Microscopy. Nano letters, 16(1), 434-9. https://doi.org/10.1021/acs.nanolett.5b04075
Cating, Emma E M, et al. "Imaging Spatial Variations in the Dissipation and Transport of Thermal Energy within Individual Silicon Nanowires Using Ultrafast Microscopy." Nano letters vol. 16,1 (2016): 434-9. doi: https://doi.org/10.1021/acs.nanolett.5b04075
Cating EE, Pinion CW, Van Goethem EM, Gabriel MM, Cahoon JF, Papanikolas JM. Imaging Spatial Variations in the Dissipation and Transport of Thermal Energy within Individual Silicon Nanowires Using Ultrafast Microscopy. Nano Lett. 2016 Jan 13;16(1):434-9. doi: 10.1021/acs.nanolett.5b04075. Epub 2015 Dec 08. PMID: 26629610.
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Nano Lett. 2016 Jan 13;16(1):434-9. doi: 10.1021/acs.nanolett.5b04075. Epub 2015 Dec 08.

Imaging Spatial Variations in the Dissipation and Transport of Thermal Energy within Individual Silicon Nanowires Using Ultrafast Microscopy.

Nano letters

Emma E M Cating, Christopher W Pinion, Erika M Van Goethem, Michelle M Gabriel, James F Cahoon, John M Papanikolas

Affiliations

  1. Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-3290, United States.

PMID: 26629610 DOI: 10.1021/acs.nanolett.5b04075

Abstract

Thermal management is an important consideration for most nanoelectronic devices, and an understanding of the thermal conductivity of individual device components is critical for the design of thermally efficient systems. However, it can be difficult to directly probe local changes in thermal conductivity within a nanoscale system. Here, we utilize the time-resolved and diffraction-limited imaging capabilities of ultrafast pump-probe microscopy to determine, in a contact-free configuration, the local thermal conductivity in individual Si nanowires (NWs). By suspending single NWs across microfabricated trenches in a quartz substrate, the properties of the same NW both on and off the substrate are directly compared. We find the substrate has no effect on the recombination lifetime or diffusion length of photogenerated charge carriers; however, it significantly impacts the thermal relaxation properties of the NW. In substrate-supported regions, thermal energy deposited into the lattice by the ultrafast laser pulse dissipates within ∼10 ns through thermal diffusion and coupling to the substrate. In suspended regions, the thermal energy persists for over 100 ns, and we directly image the time-resolved spatial motion of the thermal signal. Quantitative analysis of the transient images permits direct determination of the NW's local thermal conductivity, which we find to be a factor of ∼4 smaller than in bulk Si. Our results point to the strong potential of pump-probe microscopy to be used as an all-optical method to quantify the effects of localized environment and morphology on the thermal transport characteristics of individual nanostructured components.

Keywords: Nanowires; pump−probe microscopy; silicon; thermal conductivity; thermal diffusion

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