Fig. 3: Depth profiles of the different oxidation states of Nb.
From: Microscopic relaxation channels in materials for superconducting qubits
The profiles for the sputtered (a), HiPIMS optimized (b), and HiPIMS normal (c) Nb films were reconstructed from PES data using a maximum-entropy method algorithm. Each film shows a surface layer of a few nm of Nb2O5, a transition layer with varying concentrations of different suboxides, and the Nb metal bulk. In particular, the HiPIMS normal film shows significant concentrations of NbO and NbO2 in the transition layer and deeper penetration of NbOx into the metal.
