Nano-mechanical and microstructural characterization of MS-PVD Nb thin films – Marco Sebastiani – TFSRF-2010

Title: Nano-mechanical and microstructural characterization of MS-PVD Nb thin films
Author: Marco Sebastiani
Institution: Roma 3 University
Abstract: E. Bemporad1, M. Sebastiani1, F. Carassiti1

1Mechanical and Industrial Engineering Department, University of Rome ‘Roma Tre’, Via della Vasca Navale 79-00146 Rome, Italy

The main objective of the present study was to identify the influence of the applied bias voltage on the microstructural and mechanical properties of magnetron sputtering physical vapour deposition (MS-PVD) niobium thin films for use in superconducting resonant cavities for particle accelerators.
The microstructure and mechanical properties evolution as a function of the applied bias voltage and nature of the substrate (copper or quartz) were investigated by means of micro-hardness and nanoindentation testing, FIB/SEM, AFM and TEM techniques.
The superconducting properties (critical temperature Tc and residual resistivity) were determined by a calibrated four-contact probe and a cryogenic apparatus and then correlated to the mechanical properties.
Significant difference in terms of microstructure, surface roughness and mechanical properties were observed for biased coatings grown on different substrates. The observed differences are likely connected to the low conductivity of quartz that induces a re-sputtering effect and a consequent modification of the superconducting performances.