Different Charge Transport Mechanisms in Ti₃C₂T_x MXene Monoflakes and Multiflakes

MXenes have demonstrated their potential for various electronic and optoelectronic applications. However, our understanding of MXene charge transport mechanisms remains rather incomplete. Here, we provide a unifying picture of charge transport in monoflake and multiflake MXenes by measuring and calculating their temperature-dependent resistivity. We measure a positive temperature-dependent resistivity for both monoflakes and the out-of-plane direction of stacked multiflakes of Ti₃C₂T_x MXenes, indicating that charge transport is predominantly band-like. In contrast, a negative temperature-dependent resistivity is observed in the in-plane direction of multiflake MXenes, suggesting that charge transport is governed by thermally activated interflake hopping, which is facilitated by the presence of trapped water. These findings provide insight into the precise role of trapped water in Ti₃C₂T_x MXene resistivity, opening avenues for controlling charge transport in electronic and optoelectronic applications, especially in extremely high temperature environments.