Dresden 2020 – scientific programme

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DS: Fachverband Dünne Schichten

DS 12: Thermoelectric and Phase Change Materials

DS 12.5: Talk

Monday, March 16, 2020, 17:30–17:45, CHE 91

Phonons and thermal conductivity in Si/SiO₂ rolled-up nanostructures — •Igor Bogush^1,2 and Vladimir Fomin^3,4 — ¹Scoala Doctorala de Stiinte Fizice si Ingineresti, Institutul de Cercetare si Inovare, Moldova State University, Chisinau MD-2009, Republic of Moldova — ²Department of Theoretical Physics, Faculty of Physics, Moscow State University, 119899, Moscow, Russia — ³Department of Theoretical Physics, Moldova State University, Chisinau MD-2009, Republic of Moldova — ⁴Institute for Integrative Nanosciences, Leibniz IFW Dresden, Dresden D-01069, Germany

We have developed a differential-geometry formalism for elastodynamic equations applicable for analytical and numerical simulations of phonons in nanowires with arbitrary cross-section geometry and applied it for rolled-up nanostructures. Phonon spectrum for rolled-up Si/SiO₂ bilayer nano-structures with free boundaries is shown to have a similar form as that for unrolled flat nanostructures. Analytical calculations lead to the energy corrections proportional to the ratio of the bilayer width to the structure radius. Geometrical effects for rolled-up structures with small width/radius ratio are neglectable. Therefore realistic rolled-up structures with contacting boundaries can be simulated as flat structures preserving contacting boundary conditions in geometrically non-local sense. Phonon modes are denser for structures with more windings. On this basis we explain the experimentally observed thermal conductivity decrease with increasing number of windings. The present work is supported by the DFG grant no. FO 956/4-1.