ALPHA-QUARTZ AS A SUBSTRATE IN THERMAL PHONON RADIATION

Using the mechanical strong anisotropic α-quartz, measurements of radiation temperature as a function of phonon radiation power were performed for gold and copper radiators evaporated on the X- or Z-crystal face, respectively. The comparison with theoretical model calculations of phonon transmission across the interface yields agreement with the isotropic/anisotropic acoustic mismatch model. A strong increase in radiation temperature in comparison to linear emission models is observed at temperatures above about 40 K. We suppose that this effect is due to phonon back-scattering which leads to a back-heating of the metal film. © 1979 Springer-Verlag.