Conductive transition metal nitrides, a fascinating class of thin film materials: insights into crystal growth, elastic and optical properties

The nitrides of most of the group IVb-Vb-VIb transition metals (TM) constitute the unique category of conductive ceramics, characterized by substantial electronic conductivity, high hardness and thermal stability. They find widespread applications, such as protective hard coatings or metallization layers in microelectronics, and their promise as alternate plasmonic candidates for high temperature applications has recently aggregated interest [1].

In this talk, I will present and discuss results obtained on group IVb-VIb TM nitride (TMN) thin films deposited by reactive magnetron sputtering, including epitaxial binary layers on MgO substrates as well as polycrystalline films deposited at oblique incidence angles [2-4]. The issue of stress evolution during thin film growth will be also addressed, highlighting the role of ion bombardment in dcMS and HiPIMS discharges [3].

The influence of point defects on the phase stability and elastic properties of binary TMN will be assessed based on a comparison of experimentally measured elastic constants and computed data from first-principles calculations.

Finally, the optical properties of group IVb-TMN will be presented in the frame of their potential use as alternate plasmonic materials. In particular, a new route towards the synthesis of TMN nanowires on nano-rippled surfaces will be examined.

[1] P. Patsalas et al., Mat. Sci. Eng. R 123 (2018) 1
[2] B. Bouaouina et al., Mat. Design. 160 (2018) 338
[3] F. Cemin et al., Thin Solid Films 688 (2019) 137335
[4] G. Abadias et al., Coatings 9 (2019) 712