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

Abstract

Transition metal nitrides (TMNs) are reported as protective coatings in reactive hydrogen environments. Although the permeation of H 2 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 (NH 3 and H 2 O; based on the change in Gibbs free energy).

From Jekyll to Hyde and Beyond: Hydrogen’s Multifaceted Role in Passivation, H-Induced Breakdown, and Charging of Amorphous Silicon Nitride

“…Notwithstanding, experimental and theoretical studies have provided a number of important insights. H defects have been linked to the passivation of dangling bonds within the a-Si 3 N 4 network, − ,− based on a reduction of the observed concentration of paramagnetic centers upon increases in Si–H vs N–H concentration. , This reduction in undercoordinated Si and N has additionally been linked to the observed increase in breakdown strength and perhaps surprisingly to a decrease in the a-Si 3 N 4 film’s tensile stress . In addition, the post-deposition treatment with H leads to significant changes in the observed photoluminescence and EPR spectra. ,, The latter results suggest that H plays a dual role, leading to a reduction in midgap recombination centers while favoring or introducing others, resulting in both radiative and nonradiative recombination pathways .…”