Electronic properties and circuit applications of networks of electrochemically exfoliated 2D nanosheets

Abstract High aspect-ratio 2D materials offer promise for solution-processed electronics. However, the factors controlling exfoliation are unclear while solution-processed networks have been electrically characterized for relatively few materials. This study combines theory and experimentation to show that electrochemical exfoliation of various layered crystals with sufficient stiffness-anisotropy (Ein/Eout>1.7) produces high aspect-ratio nanosheets with intrinsic mobilities of μNS=20–75 cm²V⁻¹s⁻¹ (MoS2, WS2, WSe2, MoSe2, PtSe2, MoWSe2, MoSe2:Nb and WSe2:Nb). Impedance spectroscopy indicates that solution-deposited networks of these nanosheets have a junction-to-nanosheet resistance ratio (RJ/RNS) as low as ~3 (MoS2). These networks display n-type (PtSe2, WS2, MoS2), p-type (InTe, GaTe, MoSe2:Nb, WSe2:Nb, Tellurene, Black Phosphorus), and ambipolar behaviour (WMoSe2, MoSe2, WSe2, MoTe2), with on/off ratios and mobilities up to 10⁵ and μNet=13 cm²V⁻¹s⁻¹ respectively. Network properties are consistent with theoretical predictions that μNS/μNet=RJ/RNS+1, suggesting that further reductions in RJ will increase μNet toward the nanosheet limit (μNS). High-performing 2D materials were used to create functional circuits (WMoSe2 and WS2) including inverters, buffers, a 4-bit digital-to-analog converter, and a circuit capable of encoding and decoding 7-bit ASCII messages.