Oxide charge evolution under crystallization of amorphous Li–Nb–O films

摘要

Li–Nb–O amorphous films were deposited onto Si substrates by the radio-frequency magnetron sputtering method in an Ar environment and an Ar(60%)+O2(40%) gas mixture. A positive effective fixed oxide charge Qeffhaving negative, -Qeff, and positive,?+Qeff, components, exists in the as-grown heterostructures. -Qeffis located near the substrate/film interface, whereas?+?Qeffis determined by a deficit of Li and O (vacancies) in the bulk of Li–Nb–O films. As-grown films crystallized under thermal annealing (TA) at temperatures up to 600?°C and revealed the formation of polycrystalline LiNbO3. TA at about 520?°C resulted in the formation of the second phase LiNb3O8, increasing?+?Qeff, and compensating -Qeffentirely. The dielectric constants of the as-grown films exhibit two peaks at the annealing temperatures of 450?°C and 550?°C, which are attributed to the total crystallization and recrystallization of the LN films under TA, respectively.