Dresden 2011 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 60: Thermoelectric Materials, Thin Films, and Nanostructures II (Focused Session -- Organisers: Nielsch, Rastelli, Balke)

DS 60.3: Vortrag

Freitag, 18. März 2011, 14:30–14:45, GER 37

Cross-plane thermal conductivity of Ge/Si multilayers — •Peixuan Chen, Jianjun Zhang, Fabio Pezzoli, Mathieu Stoffel, Christoph Deneke, Armando Rastelli, and Oliver Schmidt — Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany

One of the approaches to increase the efficiency of a thermoelectric converter is the reduction of the lattice thermal conductivity k of the employed materials. By using multilayers of Ge nanodots separated by Si barriers we have shown that it is possible to precisely control the thermal conductivity of the resulting nanostructured material by simply varying the thickness of the Si spacer [1]. Here, we study the dependence of k of Ge/Si layers on the amount of deposited Ge. By gradual increasing the amount of deposited Ge, flat Ge/Si multilayers with different Ge thickness and nanodot Ge/Si multilayers with different dot density were obtained. We performed thermal conductivity measurements by using the 3-omega method and found that: (i) in the case of Ge/Si flat multilayers the total thermal resistance increases and k decreases with increasing Ge amount; (ii) in the case of Ge/Si nanodot multilayers, the change of total thermal resistance and thermal conductivity is smaller than the error bar. In order to study the effect of alloying and interface sharpness, we have performed postgrowth annealing on the nanodot multilayers. By gradual increase of the annealing temperature, the thermal conductivity of Ge/Si film increases and finally approaches the values of GeSi alloys.

[1] G. Pernot et al., Nature Materials 9, 491 (2010)