Moreira M., Fleming Y., Grysan P., Vergne C., Philippe A.M., Lunca-Popa P.
Journal of Materials Science, vol. 61, n° 4, pp. 2380-2395, 2026
Cu–Cr–O delafossite thin films were grown by metal–organic chemical vapor deposition with various extrinsic dopants (Al, Mg, Mn, Sc, Y, and Zn) targeted at 5 at% to investigate how such doping influences their structure and properties. X-ray photoelectron spectroscopy revealed that the actual dopant incorporation is well below the nominal 5%, with only Al and Sc present above quantification limit. An off-stoichiometric CuCrO<sub>2+0.15</sub> composition is determined, with no secondary phases detected. Transmission electron microscopy indicates that films grown on c-plane sapphire are epitaxial near the substrate interface but relax into a polycrystalline structure beyond 20–30 nm, while films on silicon are polycrystalline throughout. All films show high p-type conductivity (on the order of 10–10<sup>2</sup> S cm<sup>−1</sup>) attributable to the excess oxygen, with no significant variation among different dopants. Optical transmission measurements indicate a slight red-shift (~ 20 nm) of the absorption edge for all doped films, likely arising from strain effects and subtle structural disorder introduced during growth. We discuss the influence of lattice strain (sin<sup>2</sup>ψ measurements showing residual strain) and small-polaron absorption behavior in these films. Despite limited incorporation of dopants, subtle structural and optical shifts suggest that dopant precursor chemistry and growth conditions play a significant role in influencing film stoichiometry and properties.
