Magnetic, electrical and optical properties of p-type Fe-doped CuCrO2 semiconductor thin films

• First study on high-quality Cu(Cr1−xFex)O2 diluted magnetic semiconductor films.
• All thin films have a quasi-epitaxial growth orientation along the c axis.
• Room-temperature ferromagnetism comes from hole-mediated Fe3+–Cr3+ super-exchange.
• P-type conductivity is enhanced by more than one order of magnitude via Fe doping.
• All thin films show a comparatively high transparency in the visible range.

Fe-doped CuCrO2 delafossite thin films, with a c-axis quasi-epitaxial orientation, were prepared by pulsed laser deposition, exhibiting reasonably good p-type conductivity, ferromagnetism with TC well above room temperature, and comparatively high transparency in the visible range. The influence of Fe concentration (0–15 at%) on microstructure and physical properties was investigated. The substitution of Fe3+ for Cr3+ induces the lattice expansion, which is favorable for the oxygen insertion and thus produces the higher hole concentration. Accordingly the p-type conductivity is remarkably improved to 28 S cm−1. Moreover, the introduction of Fe3+ leads to the hole-mediated Fe3+–Cr3+ super-exchange coupling responsible for the room-temperature ferromagnetism. The saturation magnetization is enhanced as the Fe concentration increases, with Curie temperature ⩾550 K. Nevertheless, the transparency in the visible range does not profit from the Fe doping. The transmittance is diminished from 75% for x = 0 to 65% for x = 15 at% at the wavelength of 750 nm, which can be interpreted as the strengthened scattering of photons by charge carriers. The direct optical bandgap is modulated by 3.8% via the Fe addition. The results show that the substitution of iron for chromium is an effective way to achieve high-performance CuCrO2 thin films which are supposed to become a promising p-type transparent diluted magnetic semiconductor material.

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