Domain formation on the nonpolar lithium niobate surfaces under electron-beam irradiation: A review

Abstract

In this review, our recent results on the electron-beam domain writing (EBDW) on the nonpolar surfaces of LiNbO3 crystals of different compositions are presented. Under EB irradiation of the nonpolar surfaces, domains nucleated in irradiation points grow frontally along the polar Z-direction in a thin (of microns in thickness) surface layer; the driving force is the tangential component of space-charge fields induced by EB in irradiation points. This geometry of the experiment provides a possibility of three-dimensional (3D) characterization of domain patterns using the combination of atomic force microscopy (AFM) and second harmonic generation (SHG) confocal microscopy methods. The obtained results permitted us to relate the main characteristics of domain formation (the domain sizes and velocity Vf of the frontal motion) to the irradiation conditions (the accelerating voltage U of scanning electron microscopy (SEM), EB current I, the inserted charge Q). The domain depth Td is controlled by U via the electron penetration depth; the domain length Ld increases linearly with Q owing to the domain frontal growth by the viscous friction law. The electron emission coefficient σ affects the domain formation due to the fundamental dependence of σ on U. In the framework of current approach to EB charging of insulators, the effect of an enhanced conductance on EBDW characteristics is analyzed. The difference between EBDW characteristics observed in varied LiNbO3 compositions is discussed in the framework of the intrinsic defect structure of LiNbO3. The obtained results extend the possibility of EBDW application to a wider range of crystals