Tip-induced domain growth on the non-polar cut of lithium niobate with various stoichiometry deviations

Abstract

Appearance of wedge-like domains during local switching by a biased tip of a scanning probe microscope (SPM) was studied in non-polar cut plates of lithium niobate (LN) with the spatial distribution of the deviation of Li concentration from stoichiometry composition (Δ cLi) created by vapor transport equilibration. The voltage dependences of the domain sizes were measured in the areas of LN plates with various values of Δ cLi. It was shown that the domain length increased linearly with the voltage, while the domain base width demonstrated a square root voltage dependence. The obtained dependence of the base width was attributed to the spatial distribution of the polar component of the external field produced by a biased SPM tip. The obtained results were considered in terms of the kinetic approach to domain growth. The growth of wedge-like domains was attributed to step generation and kink motion. The velocities of the base growth and kink motion were defined by the excess of the local value of superposition of the polar components of an external field produced by a biased tip, depolarization field, and screening fields over the threshold values. The average length of the elementary steps at the domain walls revealed from the domain length to width ratio demonstrated the square root voltage dependence. It was revealed that the domain length and the width of the base inversely depended on Δ cLi. The obtained dependences of the domain growth parameters on the composition allow for improving the periodical poling technique used for the fabrication of the nonlinear optical devices.