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

Introducing hydrogen bonds into the structure of amorphous silicon nitride (a-SiNₓ:H) is attractive for dielectrics seeking extremely low thermal conductivity. Yet, experimental explorations of enhancing diffuson scattering are still insufficient. Here, a-SiN0.91:H films containing (25±5)% hydrogen as well as control samples of hydrogen-free a-SiN0.96 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-SiN0.91:H is largely suppressed to 0.8±0.10.16em0exW/(m0.16em0exK), compared with 1.8±0.30.16em0exW/(m0.16em0exK) of hydrogen-free a-SiN0.96.