Enhanced Fröhlich interaction of semiconductor cuprous oxide films determined by temperature-dependent Raman scattering and spectral transmittance

Anomalous low temperature behaviors in cuprous oxide (Cu₂O) film grown on quartz substrate have been investigated by temperature-dependent Raman and transmittance spectra. The longitudinal optical components of two Γ₁₅- phonon modes become sharper and more intense at a low temperature. It can be found that the highest-order electronic transition located at 6.4 eV exhibits a minimum transmittance near 200 K. Correspondingly, the variations from phonon intensity ratios reveal obvious anomalies with the decreasing temperature, indicating the existence of strong electron-phonon coupling mediated by Fröhlich interaction in the Cu₂O films below the temperature of 200 K.