Investigation of GeO2 thin film properties for improvement of temperature coefficient of frequency of SAW devices

We have investigated the temperature dependent elastic constants of SiO2 and GeO2. For this purpose, the phase velocity of the layered system has to be calculated using surface acoustic wave (SAW) differential delay lines on LiNbO3 substrates. Both SiO2 and GeO2 have a positive temperature coefficient of velocity. The GeO2 layer shows a significant reduction of the phase velocity compared to SiO2 which yields to an improved energy trapping of the surface acoustic wave in the overlay. However, severe stability issues arise using the GeO2 layer.