Abstract
Lithium niobate (LiNbO3) has a very large electro-optic coefficient of r33=30.8×10-12m/V, and is used as a substrate for the optical waveguide and the SAW (Surface Acoustic Wave) device. The LiNbO3 thin film is very useful for micro devices and hybridization of optical devices and electrical devices.
Lithium niobate thin films were prepared by a rf-magnetron sputtering method. Enough O2 gas pressure or enough power makes a single pahse LiNbO3. At the low O2 pressure or the low rf power, coexistence of LiNbO3 and LiNb3O8 was observed. The LiNbO3 grows epitaxially on a α-Al2O3 substrate. Crystallinity of an epitaxial LiNbO3 film on a C-cut α-Al2O3 is better than that on R-cut α-Al2O3. A lattice parameter (a-axis) of the epitaxial LiNbO3 film decreases 5% from the ordinary value. It makes the lattice mismatch decrease.
