Optical and electronic properties of one-dimensional Ca3Co2O6 thin films: Influence of the oxygen pressure

Thin films of Ca3Co2O6 were fabricated on c-cut sapphire substrates by pulsed laser deposition. The films are polycrystalline and can be grown in a large interval of oxygen pressure with significant influence on the film texture. X-ray photoelectron spectroscopy analyses indicated that only Co3+ ions are present in our samples for both octahedral and trigonal prismatic sites. The band gap measured by ultraviolet-visible light absorption experiments was found about 1.35 eV and slightly larger when the oxygen partial pressure during the deposition is increased from 10(-3) to 7x10(-2) mbar. Temperature dependent transport measurements showed a semiconducting behavior of the films and the associated band gap was found similar to the one evaluated by optical measurements and reported by theoretical studies.