High-resolution lattice parameter measurement by X-ray grazing incidence diffraction

Surface sensitive grazing incidence diffraction (GID) is used to study the interface between silicon and sapphire. A thin crystalline layer of aluminum silicate with a lateral lattice parameter slightly different from sapphire is found and quantified by model calculations. We demonstrate that in GID, very thin interface layers can be investigated for which the sensitivity for measuring small Bragg angle differences, Δθ, is enhanced by a factor of about 25 by the projection of Δθ into the plane perpendicular to the sample surface. The accuracy of the lattice parameter determination is thereby improved by at least one order of magnitude.