EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Alloys of light main group elements are attractive due to a unique combination of properties ranging from high hardness through optical transparency to high temperature stability and oxidation resistance. The properties, in the first place electrical conductivity, can be further modulated by addition of early transition metals. Amorphous Hf(M)SiBCN thin films are investigated by combining magnetron sputtering of composite B₄C–Si–Hf–M targets in Ar + N₂ plasma with ab-initio calculations [1]. First, we study the effect of the M choice and fraction on calculated mechanical properties and formation energy of MN and Hf_xM_1–xN crystals. We discuss the dependence of formation energy on the crystal structure and on the distribution of Hf and M in the metal sublattice. The calculated mechanical properties of MN correlate with those measured on HfMSiBCN. The driving force towards N incorporation, monotonically decreasing with increasing periodic-table group number of M according to the calculated formation energy of MN, very well correlates with measured electrical conductivity and extinction coefficient of HfMSiBCN. Second, we use ab-initio molecular dynamics to model the amorphous HfMSiBCN materials themselves. The calculated band gap, localisation of states around the Fermi level and bonding preferences of M atoms (in particular their tendency to bind with N) also correlate with the measured metallicity and confirm the possibility of predicting the trends of characteristics of HfMSiBCN using those of MN. Third, we identify an optimum target composition leading to hard (>20 GPa) HfMSiBCN films with a relatively high conductivity at a given extinction coefficient. The results are important for the design of hard, conductive and/or transparent high-temperature coatings.

[1] M. Matas, M. Prochazka, J. Vlcek, J. Houska, Acta Mater. 206 (2021) 116628