A metal insulator transition in YbFe4Sb12 granular thin films

Results are reported for YbFe4Sb12 thin films grown by pulsed laser deposition. Thick films (thickness > 1000 Å) show electrical transport behavior typical of bulk specimens. A metal to insulator transition is observed for films with thickness < 1000 Å. The low temperature electrical resistivity data for weakly insulating samples follow a power law (ρ(T) ∼ T− β) and a stretched exponential (ρ(T) ∼ exp[T1/T]x) for strongly insulating samples. A comparison of electrical resistivity to scanning electron microscope images indicates a correlation between the metal to insulator transition and the intergranular connectivity. Based on this result it is argued that the intergrain conductance governs the metal to insulator transition.