Investigation of the intermediate layers located between niobium substrate and lead films destined for superconducting photocathodes

The paper presents the recent studies carried out at National Centre for Nuclear Research (NCBJ) focused on improving adhesion between Pb films and Nb substrate. The impact of additional intermediate layers of Ti and Sn on the adhesion properties was also discussed. Structural and microstructural properties of the layers were investigated by using Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS). Tribological properties of the deposited layers were examined by using a profile measurement gauge and the scratch test techniques. It has been shown that the Pb layer deposited on Ti intermediate layer is characterized by the best properties in terms of smoothness and surface continuity. Apart from the classical tribological properties investigation, we demonstrated much better adhesion of a Pb layer to the Nb substrate covered with an interlayer of Ti or Sn compared to a Pb film deposited directly on Nb. Reported results prove the possibility of improvement of the lead film adhesion parameters and discuss a new development path for further work in this area.