A systematic experimental investigation was performed of the thermal conductivity of InAs wires with diameters between 40 and 1500 nm. The thermal conductivity has been shown to vary significantly between a large number of similar nanowires smaller than 250 nm. Any dependence on the diameter was obscured by this variation. On average, the thermal conductivity was 3.9±1.0 W·m-1K-1, which is a considerable reduction from bulk and shows that surface scattering is important. This value is in agreement with other measurements and theory.For wire diameters larger than 700 nm, an extremely low apparent conductivity was measured. For these wires, values near the bulk level of 27 W·m-1K-1 were expected, but values smaller than for the thin wires were obtained instead. This is a consequence of contact resistance. The contact conductance is proportional to the contact area and thus to the diameter of the wire. The conductance of the wire itself on the other hand, is proportional to the diameter squared. This means that for increasingly thick wires, the conductance of the wire becomes much larger than that of the contacts, and the overall measured conductivity becomes dominated by the contacts. This trend was reproduced in a simple qualitative model.
Diameter dependence of the thermal conductivity of InAs nanowires
van Delft, M. R. (Author). 31 Aug 2014
Student thesis: Master