Observation of ferroelectric domain structures by secondary-electron microscopy in as-grown KTiOPO4crystals

Ferroelectric domain structures of as-grown KTiOP${\mathrm{O}}_4$ crystals are observed on polished polar surfaces by the scanning secondary-electron microscopy (SEM) method. The results demonstrate a different contrast origin for domain boundaries and domains themselves. It is shown that the electron-beam irradiation in SEM causes a local heating of the ferroelectric crystal. Detailed calculations of the effects involved allow to assume that pyroelectric potentials induced by heating are opposite in sign for $C^{+}$ and $C^{-}$ domains which is the main reason for the domain contrast. Domain boundaries are revealed due to the converse piezoelectric effect and the corresponding crystal deformations of ferroelectric domains are induced by electron-beam charging.