Description
Epitaxial V thin films offer well-defined model systems for isolating strain-, dimensionality-, and interface-driven phenomena. We study epitaxial strain and lattice expansion in V(001) thin films grown on MgO(001), together with their possible effects on electronic transport. A series of Pd-capped films with V thicknesses ranging from roughly 50 to 500 Å was prepared by magnetron sputtering and characterized using X-ray reflectivity and diffraction. The films exhibit smooth interfaces, pronounced Laue oscillations, and narrow rocking curves, demonstrating high structural quality. For the thicker films, the out-of-plane lattice parameter increases approximately linearly with inverse V thickness. Below ∼100 Å, this trend is lost, and the out-of-plane lattice parameter instead shows large, nonsystematic increases, with the largest expansion exceeding 5%. Temperature-dependent four-point-probe measurements were performed on films with V thicknesses of 48, 90, and 121 Å. The 90 and 121 Å films exhibit superconducting transitions at approximately 2 and 3 K, respectively. No transition was resolved for the thinnest film in the investigated temperature range. This film exhibited a distinct resistivity behavior. The concurrence of anomalous lattice expansion and distinct transport behavior motivates further investigation of structure–transport relationships in epitaxial thin films of conventional superconductors.
