TEM characterization of an epitaxial CrO2 film deposited by the CVD method and the transition interface

Epitaxial chromium dioxide (CrO2) film was grown on sapphire Al2O3 by the chemical vapor deposition (CVD) method. The interfacial structure of the epitaxial CrO2 was characterized by transmission electron microscopy (TEM), and the spatial distribution of the chromium valence in the film was qualitatively analyzed by electron energy loss spectroscopy (EELS). An uneven transition layer with a diffraction pattern consistent with that of Cr2O3 but with an anomalously large oxygen concentration (Cr/O ≈ 0.2–0.3) was found between the CrO2 film and the substrate.