Thermal Conductivity of Suspended Si Nanostructures: Design and Fabrication

Abstract

It is presented a process for engineering suspended Si nanostructures in order to measure the thermal conductivity in Si thin films and nanowires based on standard photolithographic techniques. Unlike previous works where the nanostructure was typically grown ex situ, and then mechanically placed and contacted between the two microheaters which introduce a contact thermal resistance that difficult an easy interpretation of the experimental results by increasing the uncertainty of the measured thermal conductance of the nanostructure; in this research, the nanostructure is defined from silicon-on-insulator wafers via FIB with the objective to minimize the thermal contact resistance between the nanostructure under test and the heat sources. It has been demonstrated by experimental measurements that this suspended device is well adapted for the measurement, control and analysis of the thermal conductivity of nanoscale Si thin films and nanowires. FIB micro-fabrication strategy could be used to obtain Si based nanostructures with very low thermal conductivity which is a desirable characteristic in thermoelectric applications for thermal energy harvesting and solid state refrigeration as well.