Understanding ion and atom fluxes during high-power impulse magnetron sputtering deposition of NbC_x films from a compound target.

This article investigates the transport processes of ions and atoms during high-power impulse magnetron sputtering (HiPIMS) of niobium carbide (NbCx) films from a stoichiometric NbC compound target under varying pulse conditions. Using time-averaged mass spectroscopy (MS), optical emission spectroscopy (OES), and plasma transport modeling, the study reveals that increasing pulse power density enhances electron density and ionization, leading to a transition from carbon-rich to niobium-rich fluxes reaching the substrate. The findings show that niobium ions, particularly Nb+ and Nb2+, dominate the ion flux due to their lower ionization energy and higher ionization cross section compared to carbon ions, whose contribution is negligible. The combined diagnostics and modeling suggest that changes in film composition arise from altered transport dynamics, including scattering effects of heavier niobium species on carbon atoms, rather than from sputtering yields alone. These insights contribute to understanding and controlling film stoichiometry in HiPIMS deposition from compound targets.