Tunable superconductivity in fluorine-functionalized molybdenum carbide

Abstract

Two-dimensional transition metal carbide, molybdenum carbide (Mo2C), has been explored for applications in catalysts, energy storage devices, and superconductors. Generally, selectively etching Ga from Mo2Ga2C in HF solution is the most popular method for synthesizing Mo2CTx, where Tx represents the surface functional group (−O, –OH, –F). The functional groups on their surface strongly influence the density of states on the Fermi surface and thereby the electronic structure. Therefore, tailoring the surface functionalization demonstrates a great potential for tuning the electronic properties of Mo2C. To precisely investigate the effect of the fluorine functional group on the superconductivity of Mo2C, we adopted the topochemical method to synthesize 2D Mo2C. The fluorine-functionalized Mo2C was obtained by sintering the mixture of Mo2C and NH4F in different ratios, in which NH4F was considered a fluorine source. Due to the strong electronegativity of fluorine, the surface of Mo2C was easily functionalized by fluorine. Notably, the superconductivity of Mo2C was enhanced by increasing the fluorine content and reached the highest Tc value of 5.7 K, compared with 3.2 K of pure Mo2C. A clear magnetization hysteresis loop was observed at 2.0 K, indicating a typical type-II superconductor.