Raman scattering and photoluminescence studies on Cu2O

Cuprous oxide (Cu₂O) crystals were grown by the two step crystallization method in air atmosphere conditions from polycrystalline copper plates. The method comprises two stages; in the first one the copper plates are oxidized at 1020degC by some hours in line with its initial thickness. In the second stage the growth of large crystalline areas is promoted by annealing the Cu₂O samples at 1100degC for long periods. The effects on the crystalline structure and photoluminescence (PL) response were studied as a function of the conditions used in the second stage of the synthesis method. Raman scattering and X-ray measurements demonstrates the existence of the single phase Cu₂O. PL spectra were taken from 10 to 180 K to define the main radiative recombination paths. Besides of the near band excitonic transitions, two strong emission bands at 720 and 920 nm associated with relaxed excitons at oxygen and copper vacancies were detected. Both excitonic-vacancy bond transitions presented similar intensities which can be associated with the preparation method. The PL and the Raman scattering measurements were used to assess the evolution of the crystalline quality.