Publication No: 4867

Origin of UV-induced poling inhibition in lithium niobate crystals

H.Steigerwald¹, M.Lilienblum¹, F.von Cube¹, Y.J.Ying², R.W.Eason², S.Mailis², B.Sturman³, E.Soergel¹, and K.Buse¹

1. Institute of Physics, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany
2. Optoelectronics Research Centre, University of Southampton, UK
3. Institute of Automation and Electrometry, 630090 Novosibirsk, Russia

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.

Physics Review B (2010) Vol.82(21) pp.214105 (6pp)

doi: 10.1103/PhysRevB.82.214105