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

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 Qeff having negative, -Qeff, and positive, +Qeff, components, exists in the as-grown heterostructures. -Qeff is located near the substrate/film interface, whereas + Qeff is 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 -Qeff entirely. 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.