Polarization switching of lithium niobate with giant internal field

We report a high-field analysis on the sidewise 180 degrees domain motion i n congruent-grown Z-cut lithium niobate (LiNbO3) crystals. Polarization swi tching in reverse poling is found to take place at a smaller field strength (E), exhibit a larger switching current (i(s)), and substantiate a faster switching time (t(s)) compared with the forward poling case. Such an axial anisotropy is correlated to a defect-induced internal field E int in the bu lk and has a strength of 2.37 kV/mm and pointing along the crystal c axis. In the high-field regime ranging from 19 to 24 kV/mm, a linear dependence o f i(s) and 1/ t(s) on E is resolved. These observations are ascribed to a f ast nucleation process followed by a sidewise 180 degrees domain expansion, whose velocity can be characterized according to nu(s) = mu(s) [E - ( E-c/-E-int)], where the threshold field E-c and mobility mu(s) measure a stren gth of 18.74 kV/mm and 1.6+/-0.1 mm(2)/kV s, respectively. (C) 1999 America n Institute of Physics. [S0003-6951(99)04914-1].