Structural and magnetic properties of Co-N thin films deposited using magnetron sputtering at 523 K

TL;DR

This study investigates the phase formation and magnetic properties of Co-N thin films deposited at 523 K using magnetron sputtering, revealing temperature-dependent phase behavior and magnetic characteristics.

Contribution

It demonstrates that Co-N phases formed at 523 K are consistent regardless of reactive gas flow, contrasting with lower temperature behavior, and provides detailed structural and magnetic analysis.

Findings

Co-N phases at 523 K are identical regardless of gas flow.

Magnetic moment slightly exceeds bulk Co and is unaffected by reactive gas flow.

Phase formation at high temperature differs from lower temperature deposition.

Abstract

In this work, we studied cobalt nitride (Co-N) thin films deposited using a dc magnetron sputtering method at a substrate temperature (\Ts) of 523\,K. We find that independent of the reactive gas flow (\pn) used during sputtering, the phases of Co-N formed at this temperature seems to be identical having N \pat~$\sim$5. This is contrary to Co-N phases formed at lower \Ts. For \Ts$\sim$300\,K, an evolution of Co-N phases starting from Co(N)$\rightarrow$\tcn$\rightarrow$Co$_3$N$\rightarrow$CoN can be seen as \pn increases to 100\p, whereas when the substrate temperature increases to 523\,K, the phase formed is a mixture of Co and \tcn, independent of the {\pn} used during sputtering. We used x-ray diffraction (XRD) to probe long range ordering, x-ray absorption spectroscopy (XAS) at Co absorption edge for the local structure, Magneto-optical Kerr e ffect (MOKE) and polarized neutron reflectivity (PNR) to measure the magnetization of samples. Quantification of N \pat~was done using secondary ion mass spectroscopy (SIMS). Measurements suggest that the magnetic moment of Co-N samples deposited at 523\,K is slightly higher than the bulk Co moment and does not get affected with the \pn~used for reactive sputtering. Our results provide an important insight about the phase formation of Co-N thin films which is discussed in this work.