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Ultralow Thermal Conductivity in Polycrystalline CdSe Thin Films with Controlled Grain Size

TitleUltralow Thermal Conductivity in Polycrystalline CdSe Thin Films with Controlled Grain Size
Publication TypeJournal Article
Year of Publication2013
AuthorsFeser, Joseph P., Emory M. Chan, Arun Majumdar, Rachel A. Segalman, and Jeffrey J. Urban
JournalNano Letters
Volume13
Issue5
Pagination2122-2127
Date PublishedMay 8, 2013
ISBN Number1530-6984
Abstract

Polycrystallinity leads to increased phonon scattering at grain boundaries and is known to be an effective method to reduce thermal conductivity in thermoelectric materials. However, the fundamental limits of this approach are not fully understood, as it is difficult to form uniform sub-20 nm grain structures. We use colloidal nanocrystals treated with functional inorganic ligands to obtain nanograined films of CdSe with controlled characteristic grain size between 3 and 6 nm. Experimental measurements demonstrate that thermal conductivity in these composites can fall beneath the prediction of the so-called minimum thermal conductivity for disordered crystals. The measurements are consistent, however, with diffuse boundary scattering of acoustic phonons. This apparent paradox can be explained by an overattribution of transport to high-energy phonons in the minimum thermal conductivity model where, in compound semiconductors, optical and zone edge phonons have low group velocity and high scattering rates.

URLhttp://dx.doi.org/10.1021/nl400531f
Short TitleNano Lett.