Fig. 4: Resonant inelastic X-ray scattering (RIXS) spectra measured for the Nb films.
From: Microscopic relaxation channels in materials for superconducting qubits
a RIXS measurements at the oxygen K-edge resonance for an incident energy of 531 eV. The inset shows the O-K absorption spectrum of the sputtered film with a vertical dashed line at the resonance. b Close-up view of the RIXS spectra after subtraction of the elastic line, with the phonon density of states (DOS) calculated for Nb2O5 from45. The overall scaling factor of the DOS was chosen to aid visualization. The DOS was reported to arise from both niobium and oxygen up to ≈70 meV, and mostly from oxygen at higher energies, as represented by the blue and pink bands, respectively. The lower intensity at higher energies for the HiPIMS films indicates a larger concentration of oxygen vacancies.
