Microstructural control of the transport properties of β-FeSe films grown by sputtering

In this work, we study thickness effects in the structural and electronic properties of $\beta$-FeSe films grown by sputtering. We report a superconductor-insulator transition (SIT) as a function of thickness, for films in different substrates (SrTiO$_{3}$, MgO and Si) in a wide range of growth temperatures. As the thickness increases the evolution of the structural properties and morphology is not trivial, which can be associated to a strained initial growth. In the limit of textured thick films, the critical temperature takes values slightly higher than the expected for bulk $\beta$-FeSe, $T_c\simeq12\,$K, probably owing to growth associated stress. The electronic structure was explored by performing magnetotransport and Hall effect experiments, finding features associated to the tetragonal-to-orthorrombic structural phase transition.