Symmetric faceting of a sapphire vicinal surface revealed by grazing incidence small-angle X-ray scattering 3D mapping

Abstract

A one dimensional periodic vicinal surface of sapphire was obtained through a self-ordering process after high-temperature thermal treatment. The morphology of the surface is described as an assembly of prisms exhibiting a rectangular base and a triangular profile orthogonal to the mean surface. Careful measurements of the whole 3D reciprocal map around the origin of the reciprocal space were performed through grazing incidence small-angle X-ray scattering experiments combined with a strict orientation procedure with respect to specific crystallographic directions of the sapphire crystal. We were thus able to determine accurately the actual shape of the prisms, which exhibit an isosceles triangular profile. Such a profile symmetric with respect to a plane normal to the mean sapphire vicinal surface has never been reported.