(rough) polyimide substrates. Polyimide yields lower dark currents by more than two orders of magnitude, cf. Figure , presumably due to its rougher surface (30.7 ± 11.6 nm vs 5.5 ± 0.7 nm on glass). Such an increase in the resistance is detrimental to the RC time and the expected response time. In a similar context, Haizmann et al. have recently shown that substrate roughness and its effect on thin TMDC layers also alters the orientation of small molecules adsorbed to the TMDC surface. While the exact consequences of this alteration remain to be explored, it is likely that this will affect the chemical interactions at the interface and, thus, the efficiency with which such small molecules saturate surface defects. Therefore, a popular and powerful strategy is the insertion of an atomically smooth protection layer of hexagonal boron nitride underneath the TMDC layer. This action improves the charge carrier mobility, however at the expense of additional fabrication steps. from Ref. with permission from the PCCP Owner Societies.