Anomalous domains formed under AFM-TIP voltages in Sr0.61Ba0.39Nb2O6 crystals and their suppression

Submicro- and nanosized domain patterns are demanded by various applications. The most attractive method for fabrication of structures of these scales is the domain writing by an AFM-tip voltage Utip. The use of this method is limited by the appearance of so-called anomalous domains, in which a small area under the tip is polarized oppositely to the poling field. We present the studies of anomalous domains in zero-field cooled (ZFC) and field cooled Sr0.61Ba0.39Nb2O6 crystals. A correlation between the spatial distribution of the domain shape and the bias Ub of local hysteresis loops was found in ZFC crystals, namely, in the points with a larger Ub the anomalous domains appeared at higher Utip. Based on this correlation, we managed to prevent the formation of anomalous domains by a strong preliminary poling of the crystal resulting in an essential increase in Ub all over the bulk. The dependences of the domain diameter D on Utip and the exposure time tp are described by the unique linear and power D ∼ tpk functions, respectively. These dependences are not affected by the appearance of an anomalous region growing with Utip and tp.