Origin of UV-induced poling inhibition in lithium niobate crystals

Steigerwald, H., Lilienblum, M., von Cube, F., Ying, Y.J., Eason, R.W., Mailis, S., Sturman, B., Soergel, E. and Buse, K. (2010) Origin of UV-induced poling inhibition in lithium niobate crystals. Physical Review B, 82 (21), [214105]. (doi:10.1103/PhysRevB.82.214105).

Abstract

Short-term exposure of the +z face of LiNbO₃ crystals to focused UV laser light leads to persistent inhibition of ferroelectric domain reversal at the irradiated area, a phenomenon referred to as "poling inhibition." Different types of crystals (stoichiometric, congruent, or Mg-doped ones) are exposed, creating the so-called "latent state" and domain growth during subsequent electric-field poling is visualized. The latent state is robust against thermal annealing up to 250 °C and uniform illumination. With the tip of a scanning force microscope the coercive field is mapped, showing not only the expected resistance against domain reversal in the UV-irradiated region but also easier poling adjacent to the UV-irradiated section. These results and theoretical estimates point to the following mechanism of poling inhibition: the UV light-induced heating results in a local reduction of the lithium concentration, via thermodiffusion. The required charge compensation is provided by UV-excited free electrons/holes. After cooling, the lithium ions become immobile, and the reduced lithium concentration causes a strong local increase in the coercive field in the exposed area, while the increased Li concentration next to this area reduces the coercive field.

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Contributors

Author: R.W. Eason

Author: S. Mailis

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