Growth of LiNbO3 thin films on sapphire by pulsed-laser deposition for electro-optic modulators

Thin films of lithium niobate (LiNbO3: LN) have been successfully deposited onto c-axis sapphire substrates using the pulsed-laser deposition technique in order to grow epitaxially the expected phase. Films have been characterized by different techniques. X-ray diffraction measurements of these films deposited at temperature ranging from 600 to 750 8C and at oxygen pressures ranging from 10 to 30 Pa show the intense (0 0 0 6) peak of LN. In addition, epitaxial relationships between the LN thin films and the sapphire substrate are evidenced. The Rutherford backscattering spectroscopy measurements indicate that the films are nearly stoichiometric. The LN films are very smooth and practically free of droplets as highlighted by AFM experiments. The optical properties evaluated by m-line spectroscopy show a rather good light confinement but the grain size of crystallites in the films has to be improved to limit the optical losses.