Reversed domains in x-cut lithium niobate thin films

Abstract Periodically poled domain inversion structures with a period of 20 μm had been prepared on x-cut lithium niobate films using the external electric field. The effects of voltage and pulse number on the polarization reversal were investigated using the piezoresponse force microscopy (PFM), and the temperature stability and depth distribution of the reversed domains were studied. The minimum electric field intensity for the domain inversion growth was 28.2 kV/mm, which was higher than that of z-cut bulk lithium niobate (21 kV/mm). When the electric field intensity was large, such as 36.9 kV/mm, the reversed domain had obvious lateral expansion. Increasing the pulse number could cause the lateral expansion and the mergence of the domains. A proper choosing of voltage, pulse number and pulse duration would result in a domain with a 50% duty cycle. The temperature stability of the reversed domain was tested. When the annealing temperature was below 300°C, there was no obvious change in the domain reversal regions. When the annealing temperature was 400°C, the shape of the micro-domain structure near the negative electrode regions changed. The cone-shaped small reversed domains near the negative electrode regions disappeared after annealed for 3 h. There was no further change of the reversed domain when the annealing time exceeded 3 h. Argon ion etching was used to gradually strip the film, and the shape of the reversed domains at different depths was measured. When the domain inversion region was 200 nm below the surface, there was almost no change compared to the domain at the surface. As the depth became deeper, the domain reversal area became smaller. Compared to domain at the surface, the domain width at a depth of 412 nm was reduced by 0.5 μm in width.