Asymmetric Thermal Transport and The Influence of Contact Resistance in Telescopic Nanowires

Heat dissipation has become a critical problem in the performance of electronic devices, thus reducing their lifespans [1]. To cope with this, researchers are using several approaches like thermoelectric generators, coolers, thermal diodes, heat guides, and more [2]. A thermal diode works as a rectifier, allowing the flow of heat preferentially in one direction. In our current research, we have studied telescopic nanowires for their thermal transport and rectification capabilities [3].<br/><br/>A telescopic nanowire is a quasi-one-dimensional structure with a thick and a thin part having diameters of 300 and 90 nm, respectively, with a transition region in between. The GaAs telescopic nanowires are grown by MBE technique using the VLS mechanism [4]. Thermal conductivity measurements of one-dimensional (1D) structures were conducted using thermal bridging technique [5]. Thermal rectification ratios of up to 8% were measured as a function of applied temperature bias.<br/><br/>Further, the temperature jump at the contacts is extracted using Raman thermometry [6] while applying different temperature biases. In numerous instances within the literature, this crucial contact contribution tends to be overlooked despite its substantial influence on the determination of thermal properties. In our case, a thermal contact resistance of (2.71 ± 8.43) × 10⁸K/W was estimated and compared to reference homogeneous nanowires. This enables a corrected estimation of the rectification from the nanostructure. The thermal mapping along the nanowire axis was also done to extract the thermal conductance of the corresponding thick and thin parts.<br/><br/>These results underscore the significance of accounting for thermal contact resistance in accurately characterizing the thermal properties of nanowire-based systems. Moreover, this is the first experimental study on telescopic nanowires indicating rectification and an important contribution towards the development of thermal circuit elements.<br/><br/>[1] M. Maldovan, Nature 503, 209 (2013)<br/>[2] S. Volz, The European Physical Journal B 89, 1 (2016)<br/>[3] X. Cartoixà, L. Colombo and R. Rurali, Nano Letters 15, 8255 (2015)<br/>[4] W. Kim, A. Fontcuberta i Morral, Nano Letters 18, 49 (2018)<br/>[5] L. Shi, A. Majumdar, Journal of Heat Transfer 125<b>,</b> 881 (2003)<br/>[6] Doerk et al., ACS Nano, Vol.4, 4908-4914 (2010)