Thickness-dependent electrical resistivity evolution in Fe1−xNixSb2 thin films

Thin films of various thicknesses (40–150 nm) of Fe1−xNixSb2 with x=0.0 and 0.1 have been deposited on quartz substrate using the pulsed laser deposition technique. XRD reveals the formation of the requisite phase. The evolution of the ground state properties of FeSb2 and Fe0.9Ni0.1Sb2 as a function of film thickness (d) has been investigated via temperature (4.2–300 K)-dependent electrical resistivity (ρ(T)) studies. Interestingly, for the thinner films with d≤50, the ρ(T) of Fe1−xNixSb2 films exhibits a logarithmic temperature dependence similar to a Kondo scattering system, whereas an activated resistivity behaviour indicating the presence of energy gap is observed in thicker films (d≥90 nm). These observations may indicate transformation from Kondo insulating to Kondo metallic-type behaviour in Fe1−xNixSb2 thin film systems upon reduction of film thickness.