Preparation of LiNbO3 Thin Films by Metal-Organic Chemical Vapor Deposition

Abstract

Lithium niobate thin films were prepared on heated substrates by metal-organic chemical vapor deposition from dipivaloylmethanato lithium [Li(C111-11902)] and trichlorobis(dipivaloylmethanato)niobium(V) [Nb(C111-11902)2C18u] nder a reduced pressure of 5 Torr. In preliminary experiments, deposition behavior of Li20 and N13205 films from the respective sources was examined separately. The main reaction in Nb205 deposition was pyrolysis of [Nb(C11H19O2)2Cl3], whereas Li20 deposition involved the oxidation of [Li(C11H1902)]. The deposition rate as well as the chemical composition of LiNbO3 films were controlled by adjusting the source temperature and carrier gas flow rate. Stoichiometric LiNbO3 films with a single phase of trigonal structure were obtained when the deposition rate ratio [r=R(N13205)/R(Li20)]was controlled to be 0.4 in molar ratio at 625-650 °C under the conditions of a total gas flow rate of 300 m//min and an oxygen concentration of 50%. The films were preferentically oriented along (012) face on Si (100) substrate, while epitaxially grown films were deposited on LiTa08 (001) substrate.