Variable range hopping and thermally activated transport in molybdenum-based MXenes

The magnetotransport of freestanding, vacuum filtered, thin films of Mo₂CTz, Mo1.33CTz, Mo₂TiC₂Tz, and Mo₂Ti₂C₃Tz was measured in the 10--300-K temperature (T) range. Some of the films were annealed before measuring their transport properties. Analysis of the results suggest that---with the exception of the heavily defective Mo1.33CTz composition---in the 10- to 200-K temperature regime, variable range hopping between individual MXene sheets is the operative conduction mechanism. For Mo1.33CTz it is more likely that variable range hopping within individual flakes is rate limiting. At higher temperatures, a thermally activated process emerges in all cases. It follows that improved fabrication processes should lead to considerable improvements in the electrical transport of Mo-based MXenes.