Electrical resistivity of SmB6 thin films prepared by pulsed laser deposition with various heat treatment

Thin films of SmB 6 were prepared by PLD on several substrates kept at ambient temperature or at 600 ° C during the deposition. As shown, also post-deposition annealing at 600 ° C can be used to obtain good quality SmB 6 , but heating the substrate during deposition results in higher normalized resistance. The highest value R (2 K)/ R (300 K = 2.21 was achieved for the film deposited on a heated, polished ultra-low expansion glass ceramics substrate Clearceram®-Z. Electrical resistance measurements were performed at temperatures from 300 K down to 2 K. Numerical analysis showed that the resistivity can be described by a two-channel model with temperature activated and non-activated terms, while two energy scales were found. Activation energy W A = 3.7 − 4.8 meV, relevant in temperature interval 16 − 22 K, has been attributed to presence of a forbidden gap in SmB 6 and W D = 0.31 − 0.37 meV, which corresponds to the region 2 − 3.3 K is assumed to be a consequence of an impurity band in the forbidden gap.