Semiconducting Properties\nof Delaminated Titanium\nNitride Ti<sub>4</sub>N<sub>3</sub>T<sub><i>x</i></sub> MXene\nwith Gate-Tunable Electrical Conductivity

MXenes\nhave garnered significant attention due to their\natomically\nthin two-dimensional structure with metallic electronic properties.\nHowever, it has not yet been fully achieved to discover semiconducting\nMXenes to implement them into gate-tunable electronics such as field-effect\ntransistors and phototransistors. Here, a semiconducting Ti<sub>4</sub>N<sub>3</sub>T<sub><i>x</i></sub> MXene synthesized by\nusing a modified oxygen-assisted molten salt etching method under\nambient conditions, is reported. The oxygen-rich synthesis environment\nsignificantly enhances the etching reaction rate and selectivity of\nAl from a Ti<sub>4</sub>AlN<sub>3</sub> MAX phase, resulting in well-delaminated\nand highly crystalline Ti<sub>4</sub>N<sub>3</sub>T<sub><i>x</i></sub> MXene with minimal defects and high content of F and O, which\nled to its improved hydrophobicity and thermal stability. Notably,\nthe synthesized Ti<sub>4</sub>N<sub>3</sub>T<sub><i>x</i></sub> MXene exhibited p-type semiconducting characteristics, including\ngate-tunable electrical conductivity, with a current on–off\nratio of 5 × 10<sup>3</sup> and a hole mobility of ∼0.008\ncm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> at 243\nK. The semiconducting property crucial for thin-film transistor applications\nis evidently associated with the surface terminations and the partial\nsubstitution of oxygen in the nitrogen lattice, as corroborated by\ndensity functional theory (DFT) calculations. Furthermore, the synthesized\nTi<sub>4</sub>N<sub>3</sub>T<sub><i>x</i></sub> exhibits\nstrong light absorption characteristics and photocurrent generation.\nThese findings highlight the delaminated Ti<sub>4</sub>N<sub>3</sub>T<sub><i>x</i></sub> as an emerging two-dimensional semiconducting\nmaterial for potential electronic and optoelectronic applications.