Characterization of copper–manganese-oxide thin films deposited by dip-coating

Abstract

Thin films of copper–manganese oxide were prepared by dip-coating method and annealed between 400 and 500 °C for periods of time from 15 to 90 min. The influence of both annealing time and temperature on film composition and optical properties was studied. X-ray photoelectron spectroscopy (XPS) measurements indicated that the initially formed mixture of copper and manganese oxides leads to Cu 1.5Mn 1.5O 4 through a solid state red-ox reaction. This reaction takes place at temperatures higher than 450 °C and the full conversion of single oxides into Cu 1.5Mn 1.5O 4 needs at least 60 min to proceed. In relation to the optical properties we found that low solar absorptance ( α s∼0.6) can be associated with the mixture of single oxides whereas the formation of Cu 1.5Mn 1.5O 4 dramatically increases solar absorptance values ( α s∼0.9). The presence of Mn 3+ and Mn 4+ in octahedral sites and Cu + and Cu 2+ in tetrahedral sites is also evidenced by XPS and can explain the high conductivity of films where Cu 1.5Mn 1.5O 4 is present.