Structural, electrical, optical and magnetic properties of p-type Cu(Cr_(1-x)Mn_x)O_2 thin films prepared by pulsed laser deposition

摘要

Cu(Cr_(1-x)Mn_x)O_2 delafossite thin films (0≤x≤ 15at.%), with a c-axis quasi-epitaxial orientation, were prepared by pulsed laser deposition. The effects of Mn content on microstructure and physical properties were investigated. Both the variation of lattice constant c and X-ray photoelectron spectroscopy reveal that the Mn ions substitute for Cr~(3+) as Mn~(3+) and Mn~(4+). The proportion of Mn~(4+) is gradually increased with the Mn doping, leading to the changes of hole density and mobility. As a result, the p-type conductivity is decreased at first and then increased. The conduction mechanism is thermal activation between 130 and 300 K. It is indicated that the PLD method and the Mn~(3+)-O-Mn~(4+) and Mn~(3+)-O-Cr~(3+) double-exchange interactions are favorable to the high hole density and mobility, respectively. Meanwhile, the double-exchange interactions produce the near-room-temperature ferromagnetism. The saturation magnetization and Curie temperature are gradually increased with the Mn content. For optical properties, all thin films have a comparatively high transmittance for visible light, with the highest value 70% for x = 15 at.% at the wavelength of 750 nm. As increasing the Mn content, the transparency and direct optical bandgap exhibit the similar trend as the hole density. With the relatively balanced electrical, magnetic and optical properties, these pulsed-laser-deposition-grown Cu(Cr_(1-x)Mn_x)O_2 thin films are expected to become a promising p-type transparent diluted magnetic semiconductor material.