Phonon engineering in nanocrystal solids
Maximilian Jansen a, Nuri Yazdani a, Vanessa Wood a
a Swiss Federal Institute of Technology ETH Zurich, Switzerland
Online Conference
Proceedings of Internet Conference for Quantum Dots (iCQD)
Online, Spain, 2020 July 14th - 17th
Organizers: Quinten Akkerman, Raffaella Buonsanti, Zeger Hens and Maksym Kovalenko
Poster, Maximilian Jansen, 079
Publication date: 3rd July 2020

The assembly of semiconductor nanocrystals (NCs) into conductive and ordered solids is of interest for a wide range of electronic applications. Control of the constituent NCs allows for facile tuning of the NC solids electronic, structural and thermal properties. An important contributor to the thermal characteristics is the vibrational spectrum of the NC solid. We expect inter-particle vibrations, analogous to phonons on the atomic level, to be of importance for long range heat transport. These vibrational excitations involving multiple NCs are of a longer length scale than any other vibration type in the NC solid. By implementing a three-dimensional mass-spring model, we demonstrate effect of mass-spring disorder on these long-range vibrations. Further, we explore the parameter space of particle size and ligand type and their effect on the energy regime of the inter-particle vibrations. [1]  Additionally, we experimentally confirm their existence through inelastic neutron scattering and determine their characteristic energy scale and density.[2] We successfully demonstrate that the energy regime of these inter-particle excitations can be engineered by varying particle size and ligand type of the NCs.

Project funding was provided by the Swiss National Foundation. Inelastic Neutron Scattering measurements were performed at SINQ spallation source, Paul Scherrer Institute, Switzerland.

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