Probing the Near-Surface Regions of Magnetron Sputtered Alcrnbyzrnx High Entropy Materials Using Haxpes

Abstract

Hard X-ray photoelectron spectroscopy (HAXPES) has been used to probe the near-surface regions of AlCrNbYZrN x (N = 0 to ∼50 at.%) thin films. Photon energies of∼ 2 and 6 keV allowed non-destructive depth profiling of the passive layers as well asthe underlying regions. The metal core level spectra revealed a preferential order inwhich nitrogen interacted with the different metals, where nitrogen interacted first withY, then Zr, then Al and Nb, and lastly Cr in order of increasing nitrogen concentration.The native oxide contained oxidized species of all the metals, with higher coordinatedoxides at the outermost surface. Beneath this there was a layer of low-coordinated ox-ides or oxynitrides. After corrosion in 1.0 M HCl (2 hours of immersion followed bypolarisation from –0.7 to +0.6 V vs. Ag/AgCl (3 M KCl)), there was a transition fromlow-coordinated oxide or oxynitrides to the higher coordinated oxides for Cr, Nb and Alin films with intermediate nitrogen concentration. At the same time there was a loss ofhigh-coordinated oxides of Al and Y from the surface. The film with highest nitrogenconcentration appeared similar before and after corrosion and also at different depths inthe film, which was explained by its high porosity.

Keywords: Multicomponent alloys, passivation, Corrosion, metal nitrides, synchrotron radiation