Hydrogen effect on diffuson-dominant thermal conductivity in a−SiNx

Introducing hydrogen bonds into the structure of amorphous silicon nitride ($a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{N}}_{x}$:H) is attractive for dielectrics seeking extremely low thermal conductivity. Yet, experimental explorations of enhancing diffuson scattering are still insufficient. Here, $a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{N}}_{0.91}$:H films containing $(25\ifmmode\pm\else\textpm\fi{}5)%$ hydrogen as well as control samples of hydrogen-free $a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{N}}_{0.96}$ films were characterized using microbelt thermal bridge devices. The capability of employing a transfer length method to extract intrinsic thermal conductivity was demonstrated. Unusual thermal contact resistances and diffuson transfer lengths were corroborated, which provided evidence of diffuson crowding phenomena at bridge-end homojunctions. Two distinct features, including diffuson population-dictated thermal conductivity at low temperature and diffuson scattering-dominant thermal conductivity at high temperature were revealed. The effect of a hydrogen heavily-incorporated structure showed that room temperature thermal conductivity of $a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{N}}_{0.91}$:H is largely suppressed to $0.8\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.16em}{0ex}}\mathrm{W}/(\mathrm{m}\phantom{\rule{0.16em}{0ex}}\mathrm{K})$, compared with $1.8\ifmmode\pm\else\textpm\fi{}0.3\phantom{\rule{0.16em}{0ex}}\mathrm{W}/(\mathrm{m}\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ of hydrogen-free $a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{N}}_{0.96}$.