Growth of LiNbO₃ films on single crystal sapphire substrates using pulsed laser deposition

We report on the epitaxial growth of LiNbO₃ (112̄0) films on sapphire (112̄0) substrates using pulsed laser deposition. We have used a Li-enriched target of Li₂NbO₃ to compensate for the loss of Li at high deposition temperatures of 600-800 °C. X-ray θ-2θ scans reveal that the crystal orientation of our LiNbO₃ films is very sensitive to the deposition temperature and oxygen pressure. To obtain a single (112̄0) orientation, we need to use a deposition temperature of 800 °C and an oxygen pressure of 10^-5 Torr. Otherwise, an extra (0001) orientation of LiNbO₃ always occurs. From a rocking curve of the (112̄0) peak, we have measured a full width at half maximum of 0.3°, implying that our LiNbO₃ (112̄0) film is highly oriented. The measured dielectric constants of the LiNbO₃ (0001) and (112̄0) films at 1 MHz are 80 and 70, respectively.