Lattice Mismatch‐Driven In‐Plane Strain Engineering for Enhanced Upper Critical Fields in Mo ₂ N Superconducting Thin Films

Abstract Transition metal nitrides are a fascinating class of hard coating material that provides an excellent platform for investigating superconductivity and fundamental electron‐phonon ( e‐ph ) interactions. In this work, the structural, morphological, and superconducting properties have been studied for Mo ₂ N thin films deposited via direct current magnetron sputtering on c‐plane Al ₂ O ₃ and MgO substrates to elucidate the effect of internal strain on superconducting properties. High‐resolution X‐ray diffraction and time‐of‐flight elastic recoil detection analysis confirm the growth of single‐phase Mo ₂ N thin films exhibiting epitaxial growth with twin‐domain structure. Low‐temperature electrical transport measurements reveal superconducting transitions at ≈5.2 and ≈5.6 K with corresponding upper critical fields of ≈5 and ≈7 T for the films deposited on Al ₂ O ₃ and MgO, respectively. These results indicate strong type‐II superconductivity, and the observed differences in superconducting properties are attributed to substrate‐induced strain, which leads to higher e‐ph coupling for the film on MgO substrate. These findings highlight the tunability of superconducting properties in Mo ₂ N films through strategic substrate selection.