The use of SiO2 sublayers beneath titanium transition edge sensors for the purpose of phonon spectroscopy

We have investigated the effect of thin SiO2 sublayers on the transmission of phonons into titanium transition edge sensors (TESs) fabricated on high-resistivity (100) float zone (FZ) silicon substrates. The response of a TES on native oxide is compared to that of an adjacent TES on a thermally grown SiO2 sublayer. Latching current measurements indicate that thermal phonons are not attenuated by the film. However, pulse data from X-ray scattering experiments suggest that high frequency phonons are preferentially scattered.