Phonon transport properties depending on crystal orientation analyzed by nanoindentation using single-crystal silicon wafers

The influences of crystal orientation on phonon transport properties were analyzed by nanoindentation using single-crystal Si wafers. The elastic moduli and group velocities of [100]-oriented Si were lower than those of [111]-oriented Si. The phonon mean free path (MFP) exhibited the opposite trend. Phonon transport properties were calculated using the Hooke's law with a stiffness tensor. The measured phonon MFP of the [100]-oriented Si were approximately 13% different from the corresponding semi-theoretical values, while those of the [111]-oriented Si were comparable to the corresponding semi-theoretical values, according to the difference in atomic density of each crystal plane of Si.