The microscopic structure of the polar (000$\overline{1}$) and (0001) surfaces of lithium niobate is investigated by atomic-resolution frequency modulation atomic force microscopy and first-principles calculations. It is found that the surface reconstructs at annealing temperatures sufficiently high to drive off external adsorbates. In particular a ($\sqrt{7}\times \sqrt{7}$)$R$19.1${}^{\circ }$ reconstruction is found for the (000$\overline{1}$) surface. Density-functional theory calculations show that—apart from the $(\sqrt{7}\times \sqrt{7})$—a series of adatom-induced surface reconstructions exist that lower the surface energy and reduce the surface charge.

• Received 2 June 2013

DOI:https://doi.org/10.1103/PhysRevB.88.115422