Radiationless Raman versus Anger behavior at the Cu L-3 resonance of CuO and Cu2O

We have investigated the behavior of the 2p3p3p and 2p3s3p Anger lines of C uO and Cu2O scanning the photon energy across the Cu L-3 resonance. For bot h samples, when the excitation energy is below the L-3 resonance, we observ e the 2p3p3p and 2p3s3p peaks at constant binding energy. This behavior is typical of nonradiative resonant Raman scattering. If the photon energy is raised above the L-3 maximum, the two samples behave in different ways. In CuO, the Auger peaks are always observed at constant binding energy, while in Cu2O their kinetic energy first reaches a maximum at correspondence with the absorption threshold, and then stabilizes at a value slightly higher t han the off-resonance Auger peaks. These differences are interpreted in ter ms of the different electronic structure of the Auger intermediate state at resonance. In CuO, the intermediate state corresponds to a single 2p(3/2) core hole, with the Cu 3d band completely filled. On the contrary, in Cu2O the intermediate state is represented by the combination of a 2p(3/2) hole with a 4sp electron in strong interaction with the O-2sp valence band. In C uO, for photon energies higher than 1.5 eV above the L-3-edge maximum, the constant binding energy radiationless Raman peaks are accompanied by consta nt kinetic energy replicas. These are attributed to the relaxation of the A uger intermediate state through electron-hole pair generation across the ba nd gap of the material. Satellites that could be associated to relaxation p recesses involving energies smaller than the band gap are not resolved. No variation of the lineshape of the Anger peaks is observed as a function of the sample temperature, indicating that different densities of thermally ac cessible excitations do not have a strong influence on the recombination pr ocess of the core hole.