Temperature stability of c-axis oriented LiNbO3/SiO2/Si thin film layered structures

Theoretical calculations have been performed for the temperature stability of the c-axis oriented LiNbO3 thin film layered structures on passivated silicon (SiO2/Si) substrate with and without a non-piezoelectric SiO2 overlayer. The phase velocity, electromechanical coupling coefficient and temperature coefficient of delay (TCD) have been calculated. The thicknesses of various layers have been determined for optimum SAW performance with zero TCD. The presence of a non-piezoelectric SiO2 overlayer on LiNbO3 film is found to significantly enhance the coupling coefficient. The optimized results reveal that a high coupling coefficient of K-2 = 3.45% and a zero TCD can be obtained in the SiO2/LiNbO3/SiO2/Si structure with a 0.235 lambda thick LiNbO3 layer sandwiched between 0.1 lambda thick SiO2 layers.