Effective charge in LiNbO$_{3}$ films fabricated by radio-frequency magnetron sputtering method

Amorphous Li–Nb–O films were deposited onto Si substrates by radio-frequency magnetron sputtering method. The fabricated heterostructures demonstrated the presence of effective oxide charge $Q_{\operatorname{eff}}$ having both negative and positive components. Thermal annealing (TA) of as-grown heterostructures leads to the crystallization of a Li–Nb–O system with the formation of LiNbO$_{3}$ films. The $Q_{\operatorname{eff}}$ changes with TA, reaching a minimum at the annealing temperature of about 470$^\circ$C, corresponding to the entire film's crystallization.