Synthesis and Characterization of Single‐Phase ReN Thin Films

Herein, a systematic study is reported on the synthesis and characterization of single-phase rhenium nitride (ReN) thin films grown using a reactive dc magnetron sputtering (R-dcMS). ReN thin films are expected to be superhard (bulk modulus ≈ 400 GPa) and superconducting (Tc ≈ 5 K). Since the formation enthalpy of ReN ≈ –0.14 eV is comparatively high, a stringent control of growth parameters such as partial N2 gas flow () and growth temperature (Ts) is necessary to achieve an impurity free and single-phase ReN. The and the Ts are systematically varied during the R-dcMS process to find the optimal conditions for growth of ReN phase. Resulting samples are studied using X-ray reflectivity to determine the deposition rate, density, and roughness. The crystal structure and depth profile of ReN thin films have been probed using X-ray diffraction and secondary ion mass spectroscopy. The electronic structure is studied using hard X-ray photoelectron spectroscopy and N K-edge X-ray absorption near edge structure. The superconducting transition temperature (Tc) is found to be 3.3 K from the zero field electrical resistivity measurement. The present work constructs a phase diagram to identify the optimal conditions for forming single-phase ReN films.