Out-of-plane charge transport anomalies in polytypes of NbS₂

Tuning interlayer coupling in quasi-two-dimensional materials is a powerful tool for realising novel electronic states for potential applications in electronic and optical devices. Crucial information regarding the underlying interactions can be obtained by probing the c-axis resistivity¹. We present the case of the 2H and 3R polytypes of NbS₂, which have the same in-plane structure but different stacking of the layers and as a result exhibit very contrasting charge transport properties. By utilising focused-ion-beam-assisted sample preparation we were able to unambiguously probe the in-plane and out-of-plane resistivities of the compounds. The corresponding anisotropies are substantially lower than has been thought before. Furthermore, we show a number of previously unobserved features, including non-monotonic temperature dependence of resistivity and negative longitudinal magnetoresistance. We suggest that the stacking faults, occurring naturally in the studied compounds², are the primary cause of the aforementioned behaviours.

1. Martino, E. et al. https://arxiv.org/abs/1910.03817 (2019).
2. Katzke, H. Z. Kristallogr. 217, 127–130 (2002).