UV laser-induced ferroelectric domain structures investigated by piezoresponse force microscopy

Ferroelectric domains have been generated on the +z and the ^-z faces of congruent undoped lithium niobate (LiNbO₃) single crystals by direct UV writing using a continuous wave (c.w.) frequency doubled argon ion laser (lambda=244 nm). The width of the domains was observed to depend on the intensity of the laser beam. Interestingly, also the contrast of the domains seen by piezoresponse force microscopy (PFM) was observed to increase with higher laser intensity. The contrast difference could be attributed to a difference of the depth of these surface domains as the depth sensitivity of the PFM is ~1 mum for LiNbO₃.