Preparation of crystalline LiNbO sub 3 films with preferred orientation by hydrolysis of metal alkoxides

Abstract

Homogeneous and stoichiometric LiNbO{sub 3} films were prepared on substrates from double alkoxide solutions by a dip-coating method. Structural control of the double alkoxide solution is critical in synthesizing crystalline stoichiometric LiNbO{sub 3} films. The coordination states of alkoxides in solution were monitored by Ir and NMR spectroscopy. A viscosity of the double alkoxide solution was adjusted to a value of 6 {times} 10{sup {minus}3} to 7 {times} 10{sup {minus}3} N{center dot}s/m{sup 2} (6 to 7 cP) by partial hydrolysis and the concentration of the solution. Amorphous LiNbO{sub 3} films prepared on Si- or sapphire-single-crystal substrates from controlled alkoxide solutions began to crystallize at temperatures as low as 250{degree}C. Films on sapphire substrates crystallized with the preferred orientation along each orientation, such as (001), (110), and (012) but not on Si(100) and Si(111) substrates. The crystallinity of the initial thin-film coating of LiNbO{sub 3} significantly influenced the crystallization of films deposited subsequently.