X-ray investigation of lateral hetero-structures of inversion domains in LiNbO3, KTiOPO4and KTiOAsO4

Abstract

In this paper periodically domain-inverted (PDI) ferroelectric crystals are studied using high-resolution X-ray diffraction. Rocking curves and reciprocal-space maps of the principal symmetric Bragg reflections in LiNbO3(LN) (Λ = 5 µm), KTiOPO4(KTP) (Λ = 9 µm) and KTiOAsO4(KTA) (Λ = 39 µm) are presented. For all the samples strong satellite reflections were observed as a consequence of the PDI structure. Analysis of the satellites showed that they were caused by a combination ofcoherentandincoherentscattering between the adjacent domains. Whilst the satellites contained phase information regarding the structure of the domain wall, this information could not be rigorously extracted withouta prioriknowledge of the twinning mechanism. Analysis of the profiles reveals strain distributions of Δd/d= 1.6 × 10−4and 2.0 × 10−4perpendicular to domain walls in KTP and LN samples, respectively, and lateral correlation lengths of 63 µm (KTP), 194 µm (KTA) and 10 µm (LN). The decay of crystal truncation rods in LN and KTP was found to support the occurrence of surface corrugations.