Preparation and characterization of LiNbO3 thin films produced by chemical-vapor deposition

Lithium niobate [LiNbO3 (LN)] thin films with good surface morphology and crystallinity have been epitaxially grown on lithium tantalate [LiTaO3 (LT)] substrates by chemical-vapor deposition using lithium dipivaloylmethane [Li(C11H19O2)] and niobium pentaethoxide [Nb(OC2H5)5] without postannealing. The Li/Nb ratio of LN thin films was easily controlled by adjusting the Nb source temperature, and it is possible to prepare LN thin films with stoichiometric composition (Li/Nb=1). The crystallinity of LN thin films greatly depends on substrate temperature and surface orientation of the LT substrate. It becomes better with increasing substrate temperature and is equivalent to a single crystal at 700 °C. It also becomes better in the order of (012), (110), and (001) planes of the LT substrate. The properties of surface acoustic wave propagation can be improved by preparing the LN thin film on the LT substrate. The electromechanical coupling factor k2 of LN/(012)LT is 0.52%, and is greater than that of the (012)LT substrate alone, 0.081%. The sound velocity of LN/(012)LT calculated from the central resonant frequency is 3200 m/s, and this value is greater than that of the (012)LT substrate by itself, 3140 m/s.