Environmental Stability and Electronic Properties of Individual Flakes of Ti₂CT_x MXene

Ti2CTx MXene holds promise for high‑performance electronics, yet its intrinsic electronic properties have remained unclear because large, stable flakes are difficult to obtain and monolayers rapidly oxidize in air. Here we report a scalable LiF‑HCl etching and gentle delamination protocol that yields Ti₂CT_x monolayers with lateral dimensions of 10–15 µm (up to 40 µm) suitable for device fabrication. Systematic electrical measurements on single flakes reveal a stark contrast between environmentally vulnerable monolayers and more robust multilayer samples. Monolayer devices exposed to ambient conditions within hours become partially oxidized, displaying low conductivity, electron mobility ≈0.2 cm² V⁻¹ s⁻¹ and semiconducting temperature coefficients (dR/dT < 0). In contrast, multilayer flakes retain their metallic character, achieving conductivities of ~3 700 S cm⁻¹ and mobilities of ~1.6 cm² V⁻¹ s⁻¹ with dR/dT > 0, values among the highest reported for MXenes and consistent with theoretical predictions for Ti₂CT_x (Tx = –F, –OH, =O). Film studies corroborate that thicker assemblies exhibit superior environmental stability. In addition to providing insights into the electronic properties of Ti₂CT_x, this study outlines a strategy for electrical characterization of individual flakes of MXenes with poor environmental stability, which involves rapid processing of the material as well as a direct comparison of monolayer and few-layer flakes.