Depth profiling of thin ITO films by grazing incidence X-ray diffraction

Abstract

Tin-doped In2O3 (ITO) films, deposited at room temperature by d.c. magnetron sputtering, display a double-layer structure after post-deposition annealing. The films consist of a stress-free polycrystalline bottom layer and a severely stressed polycrystalline top layer. Standard 2θ − θ X-ray diffraction reveals doublet-type peak profiles. Asymmetric Bragg X-ray diffraction with a grazing angle of incidence was used to assess the stress-depth relation. Measuring diffraction peak positions of the doublet peak profiles and correcting for refraction has enabled us to determine Young's modulus E and Poisson' s ratio v for ITO. The thicknesses of the two constituent layers of the ITO film can be determined by measuring the integrated peak intensities as a function of incidence angle and correcting for texture. The X-ray diffraction results were compared with a single cross-sectional transmission electron microscopy analysis.