ABSTRACTWe compare electron-beam writing of domains and domain patterns in He-implanted planar optical waveguides fabricated on X-cut LiNbO3 crystals to the results of domain writing on the nonpolar surfaces in unimplanted LiNbO3. The characteristics of written patterns, in particular the exposure dependences of the domain length L and spatial regularity of written domain gratings depend on the relation between the domain depth Td controlled by the acceleration voltages U, and thickness D of the optical barrier, determined by He-ion beam energy. An increased average L in domain gratings as compared to isolated domains is discussed with account for dependence of the electron emission coefficient σ on U.