Field Emission Performance of 2D Ti ₂ CT _x (T _x = O ₂ , F ₂ , O–F) MXene: Experimental Insights and Theoretical Endorsement

Field emission (FE) is an important electron emission mechanism for vacuum microelectronic devices; however, conventional emitters often exhibit high turn-on fields, limited emission stability, and degradation during prolonged operation. Two-dimensional MXenes have recently emerged as promising FE materials due to their remarkable electrical conductivity, comparatively low work function, and tunnelable surface terminations. Nevertheless, most studies have focused on Ti 3 C 2 T x MXene, while other compositions such as Ti 2 CT x remain largely unexplored, particularly regarding the influence of surface terminal groups on their electronic and emission properties. Herein, Ti 2 CT x (T x = −F 2, −O 2, −OF) MXene was synthesized via selective chemical etching of the Ti 2 AlC MAX phase and investigated for its FE characteristics. The material exhibits a polycrystalline hexagonal layered structure with a high specific surface area of 349.02 m 2 g –1 . Ti 2 CT x MXene demonstrates excellent FE performance with a low turn-on field of 1.56 V μm –1 and a threshold field of 2.0 V μm –1 (at 10 μA cm –2 ), along with a stable emission for 4 h. Density functional theory calculations further reveal that surface terminations strongly influence the electronic structure and work function, with the experimental value of 4.66 eV closely matching the −F 2 termination. These results highlight Ti 2 CT x MXene as a promising material for stable and efficient FE applications.