Chemical Interaction of Hydrogen Radicals (H*) with Transition Metal Nitrides

Abdul Rehman; Robbert W E van de Kruijs; Wesley T E van den Beld; Jacobus M Sturm; Marcelo Ackermann

doi:10.1021/acs.jpcc.3c04490

Chemical Interaction of Hydrogen Radicals (H*) with Transition Metal Nitrides

J Phys Chem C Nanomater Interfaces. 2023 Sep 6;127(36):17770-17780. doi: 10.1021/acs.jpcc.3c04490. eCollection 2023 Sep 14.

Authors

Abdul Rehman¹, Robbert W E van de Kruijs¹, Wesley T E van den Beld¹, Jacobus M Sturm¹, Marcelo Ackermann¹

Affiliation

¹ Industrial Focus Group XUV Optics, MESA+ Institute for Nanotechnology, University of Twente, Drienerlolaan 5, Enschede 7522NB, Netherlands.

Abstract

Transition metal nitrides (TMNs) are reported as protective coatings in reactive hydrogen environments. Although the permeation of H₂ through TMN coatings is well reported, their reducibility in H* environments is less investigated. In this work, we categorize the interaction of H* with ambient exposed TiN, ZrN, HfN, VN, NbN, and TaN thin films at 700 °C into three classes. We find that in TiN and VN samples, H*-induced reduction was limited to the surface (≈ top 2 nm). Significant denitridation was observed in ZrN and HfN samples beneath the surface, along with an increase in the transition metal oxide (TMO_x) fraction. Denitridation was observed in NbN and TaN samples as well, but the increase in the TMO_x content was less than for ZrN and HfN. We propose a model in three steps: hydrogenation, formation of volatile species, and diffusion of subsurface atoms to the surface. We show that the interaction of H* with TiN, ZrN, HfN, VN, NbN, and TaN with partially oxidized surfaces can be explained using the preferred hydrogenation pathway (based on the work functions) and the thermodynamic driver for forming volatile species (NH₃ and H₂O; based on the change in Gibbs free energy).