Abstract:
Optothermal Raman spectroscopy is a steady-state technique for measuring the
thermal conductivity of materials. In this method, Raman spectroscopy is used to
measure the local temperature rise of the sample, using the excitation laser as a
heat source. Optothermal Raman is used to measure the thermal conductivity of
silicon-carbon nanograins mixtures as a function of carbon and silicon content, to
determine the effect of boundaries on nanoscale heat transport experimentally. It
is found that the thermal conductivity of silicon-carbon nanograins mixtures varies
rapidly between 4.3 W/m.K and 15.3 W/m.K as a function of silicon and carbon
content. We thus demonstrate that optothermal Raman spectroscopy is an effective
non-destructive method for measuring the thermal conductivity of random materials
and that the thermal conductivity of silicon-carbon nanograins mixtures is highly
sensitive to the ratio of silicon-to-carbon content. In other words, we found that
grain boundary density significantly affects nanoscale heat transport. We hope that
our work will pave the way for an experimental study of nanoscale thermal resistance,
which has remained obscure to scientists
