Mechanical strain dependence of thermal transport in amorphous silicon thin films

Recent computational studies predict mechanical strain-induced changes in thermal transport, which is yet to be validated by experimental data. In this article, we present experimental evidence of an increase in thermal conductivity of nominally 200-nm-thick freestanding amorphous silicon thin films under externally applied tensile loading. Using a combination of nanomechanical testing and infrared microscopy, we show that 2.5% tensile strain can increase thermal conductivity from 1 to 2.4 W/m-K. We propose that such an increase in thermal conductivity might be due to strain-induced changes in microstructure and/or carrier density. Microstructural and optical reflectivity characterization through Raman and infrared spectroscopy are presented to investigate this hypothesis.