Growth of Li 2 B 4 O 7 films on LiNbO 3 and LiTaO 3 substrates

Lithium niobate (LiNbO 3 : LN) and lithium tantalate (LiTaO 3 : LT) are widely used for bulk and surface acoustic wave devices because of their excellent piezoelectricity and high mechanical Q-factors. However, the frequency temperature coefficients (TCF) of these crystals are relatively large. On the contrary, lithium tetraborate (Li 2 B 4 O 7 : LBO) has high piezoelectricity and a positive TCF. We investigated a method of growing LBO single crystal films on LN and-/or LT substrates in order to achieve piezoelectric substrates with high electromechanical coupling and low TCF.