MOCVD of ZrN: Tuning Thin Film Properties Towards Catalytic Applications

Abstract

Transition metal nitrides (TMN) have gained increasing attention over recent years as active materials for energy related applications including catalysis and energy storage. They feature high electrical conductivities, wide optical band gaps and superior chemical stability.[1] In particular, ZrN has been recently identified as a promising material for a range of potential applications that include plasmonic devices,[2] as a catalyst for the oxygen reduction reaction (ORR),[3] and as a catalyst for the nitrogen reduction reaction (NRR),[4] due to its appealing electronic properties, while being cheap and abundant compared to commonly used noble metals.[1,5] The fabrication of ZrN on large scale under moderate process conditions, with the required properties for catalytic applications, motivates the use of chemical vapor deposition (CVD) as the method of choice. Moreover, with the variation of process parameters that includes precursor choice and growth temperature, it is possible to tune the surface features as well as composition of the layers that are suitable for catalytic applications.In this study, we have employed metal organic chemical vapor deposition (MOCVD) to synthesize ZrN layers on Si and glassy carbon (GC) substrates in the temperature range of 550 – 850 °C. The influence of the nature of the precursor and deposition temperature on the structure, composition and surface morphology of the ZrN layers was systematically studied. Oriented ZrN layers with facetted grain morphology were obtained. ZrN films of different thickness were analyzed by complementary methods including X-ray diffraction (XRD) (Figure 1 a)), Raman spectroscopy, Rutherford backscattering spectrometry (RBS) (Figure 1 b)), nuclear reaction analysis (NRA), scanning electron microscopy (SEM) (Figure 1 c)), and X-ray photoelectron spectroscopy (XPS). Based on the detailed film analysis, catalyst surfaces were modeled by DFT calculations. The NRR activity and selectivity towards the competing hydrogen evolution reaction (HER) were evaluated by first principles simulations and electrochemical experiments. This preliminary study on material fabrication and theoretical investigations lays a foundation for the investigation of ZrN for NRR applications for future studies.