Temperature and pressure effects on the spectral reflection of layered polar dielectrics

Official URL: http://dx.doi.org/10.1088/2053-1591/aade33

In addition to their ability to reflect radiation in the Reststrahlen band, polar dielectrics are known for their good thermo-mechanical properties for potential use as aerospace materials in extreme environments. Here, we investigate the effect of temperature and pressure on the spectral reflection from single layer polar dielectrics (GaN and SiC) and heterojunction polar stacked dielectric layers. Stacked layers of polar dielectrics are expected to yield four distinct peaks in the reflection spectrum. However, our results show that the transverse optical phonon resonance of the substrate destructively damps the longitudinal phonon resonance of the over layer. Depending on the layer thickness, the longitudinal phonon resonant frequency of the thin polar-dielectric layer cannot be observed in the reflection or transmission spectrum of heterojunction polar stacked dielectric layers. Our results further indicate that increasing the temperature leads to a wider Reststrahlen band for GaN than SiC, although the spectral broadening is more prominent for SiC than GaN under applied external pressure.