nature06381-s1

nature06381-s1 - doi 10.1038/nature06381 SUPPLEMENTARY...

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Enhanced Thermoelectric Performance of Rough Silicon Nanowires Allon I. Hochbaum 1 *, Renkun Chen 2 *, Raul Diaz Delgado 1 , Wenjie Liang 1 , Erik C. Garnett 1 , Mark Najarian 3 , Arun Majumdar 2,3,4 , Peidong Yang 1,3,4 1 Department of Chemistry, University of California, Berkeley, CA 94720 2 Department of Mechanical Engineering, University of California, Berkeley, CA 94720 3 Department of Materials Science and Engineering, University of California, Berkeley, CA 94720 4 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 *These authors contributed equally to this work Supplementary methods and discussion Thermal bonding of nanowires Excess thermal anchor deposition by FIB bonding is in the form of a Pt-C composite, is due to low intensity secondary electron emission away from the irradiated region, and is unavoidable. Fig. S1a shows a TEM of such deposition on two bridging Si nanowires near the midpoint between both membranes. The Pt is deposited in the form of SUPPLEMENTARY INFORMATION doi: 10.1038/nature0 6 381 www.nature.com/nature 1
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nanoparticles embedded in an amorphous C matrix – a product of the organic ligand decomposition. The nanoparticles do not form a continuous film, and the contribution of the Pt-C composite to thermal conductance is negligible, as demonstrated by repeated bonding and excess deposition on the same nanowire after a first measurement (Fig. S1b). The temperature-dependent thermal conductivity from both measurements is the same. Calibration of nanowire measurements To demonstrate the accuracy of these thermal transport experiments, the k of SiO 2 nanowires was measured with this apparatus. SiO 2 nanowires were prepared by dry oxidation of VLS-grown Si nanowires at 1000 ° C for 24 hours. TEM analysis of the oxidized wires showed no crystalline material remaining and energy dispersive X-ray spectroscopy confirmed the presence of abundant O within the nanowires. The k of these wires (Fig. S1c) is very close to that of bulk amorphous SiO 2 , which was expected since the mean free path of phonons approaches that of the inter-atomic spacing in an amorphous solid. Consequently, no increased boundary scattering was observed as compared to bulk. The experimental error shown in the main text plots of k was derived from these measurements using the average error around room temperature (~ 8% at 290K, decreasing with temperature).
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This note was uploaded on 05/21/2010 for the course MS Thermoelec taught by Professor Snyder during the Spring '10 term at Caltech.

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nature06381-s1 - doi 10.1038/nature06381 SUPPLEMENTARY...

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