Diversity of electronic transitions and photoluminescence properties of p -type cuprous oxide films: A temperature-dependent spectral transmittance study

Cuprous oxide films have been deposited on quartz substrates by a sol-gel method under various annealing temperatures. The X-ray diffraction analysis and Raman scattering show that all the films are of pure Cu₂O phase. From comparison of photoluminescence with 488 and 325 nm laser excitations, the electronic transition energies and intensities present the annealing-temperature dependent behavior. The electronic band structures of the Cu₂O film annealed at 800 °C, especially for the contribution of exciton series and high energy transitions, have been investigated by temperature dependent transmittance. The extracted refraction index and the high frequency dielectric constant both abruptly decrease until the temperature rises up to 100 K. Six transitions can be clearly identified and the red shift trend of E_o3-E_o5 transition energies with increasing the temperature can be found. Moreover, the anomalous behavior takes place at about 200 K from the E_o6 transition. The singularities indicate that the change in the crystalline and electronic band structure occurs as the temperature near 100 K and 200 K for the film.