Precipitation of lamellar phases in H: LiNbO3 layers

Abstract

Structural defects in a surface layer of the proton-exchanged waveguide layer formed on a substrate prepared from an X-cut lithium niobate single crystal are revealed and investigated using scanning electron microscopy and optical interference profilometry in combination with selective etching. It is established that these structural defects, which are oriented along the [0 15 1] crystallographic direction and matched to the matrix (the β phase of the HxLi1 − xNbO3 solid solution) through a network of misfit dislocations, consist of one of the HxLi1 − xNbO3 phases precipitated in the form of lamellar regions ∼100 nm thick. Precipitation of lamellar phases precedes the destruction of the surface of the proton-exchanged layer. The presence of residual internal stresses in the LiNbO3 initial crystal favors the formation of the lamellar phases.