Residual compressive stress induced infrared-absorption frequency shift of hexagonal boron nitride in cubic boron nitride films prepared by plasma-enhanced chemical vapor deposition

The effects of compressive stress on the TO phonon frequencies of hexagonal boron nitride (hBN) in cubic BN (cBN) films were investigated using infrared absorption spectroscopy, showing that the B–N stretching vibration of hBN at 1380 cm^-1 shifted to high wavenumbers under biaxial compressive stress with the rate 2.65 cm^-1 per GPa, while the B–N–B bending vibration near 780 cm^-1 shifted to low wavenumbers with the rate -3.45 cm^-1/GPa. The density functional perturbation theoretical calculation was carried out to check the above phonon frequencies under stress for two typical orientations of hBN crystallite. The results are shown to be in fair agreement with the experimental data. Our results suggest that the residual compressive stress accumulated in cBN films can be evaluated from the IR peak position near 780 cm^-1.