Preparation and characterization of CrO₂ films by Low Pressure Chemical Vapor Deposition from CrO₃

Highly oriented CrO₂ thin films have been heteroepitaxially grown on TiO₂ rutile (110), (100) and (001) single crystalline substrates, by Low Pressure Chemical Vapor Deposition from CrO₃ as precursor and flowing oxygen as carrier gas, under a pressure of 67 Pa. The experimental conditions were fine tuned by depositing on polycrystalline Ti foils, to improve the purity of the films and the deposition rate. A maximum deposition rate of 175 nm h⁻¹ was obtained. The composition and texture of films, up to 2 μm thick, have been determined by X-ray diffraction (XRD) and Micro Raman, while their microstructure has been examined by Scanning Electron Microcopy and Atomic Force Microscopy, and their magnetic behavior has been tested by superconducting quantum interference device magnetometry. These techniques reveal that the phase purity, texture, microstructure and thickness of these films are dependent on the crystalline face of the rutile substrate and the deposition temperature. Thus, microscopy techniques, XRD and Raman spectroscopy confirm that highly textured CrO₂ films were always obtained on the three rutile substrate faces when deposition temperature ranges between 616 K and 636 K. But these techniques also show that CrO₂ films are unpurified with inclusions or patches of Cr₂O₃, for the most of the substrates and especially at high deposition temperatures. Magnetic measurements conclusively demonstrate that pure CrO₂ films are only obtained when TiO₂ (110) is used as a substrate. - Highlights: • CrO₂ films were grown by Low Pressure Chemical Vapor Deposition by using CrO₃. • CrO₂ films were grown at pressures as low as 67 Pa. • Pure and highly textured CrO₂ films were obtained on TiO₂ (110) rutile substrates. • Minor amounts of Cr₂O₃ were found on TiO₂ (100) and (001) rutile substrates