High-resolution lattice parameter measurement by X-ray grazing incidence diffraction - Application to the interface of silicon on sapphire

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