Electron beam domain writing in reduced LiNbO3 crystals

Electron-beam domain writing (DEBW) on the nonpolar surfaces of reduced LiNbO3 crystals was studied. Essential distinctions were found as compared with DEBW in as-grown congruent LiNbO3 crystals (CLN). The threshold dose Dthr of domain emerging in reduced LiNbO3 (RLN) exceeds essentially Dthr in CLN, which is related to a decreased space-charge Qsc in the irradiated area due to the increase of the bulk leakage current ILbulk. The shape of domain gratings in RLN differs from that in CLN because of an increased dark conductivity. The velocity of domain-wall frontal motion in RLN is more than by a factor of 20 lower than in CLN, which is due both to a decreased Qsc and to an essential reduction of the domain-wall mobility. All these effects related to a fundamental change of the charge transport in RLN are discussed in the framework of the current model of the LiNbO3 defect structure. The results obtained show that the only path to realize DEBW in crystals with varied conductance is the adjustment of EB current density.