Chalcogenide halide ScXY (X = S, Se, Te; Y = Cl, Br, I) monolayers as gate dielectrics for two-dimensional field-effect transistors

In recent years, rare-earth oxyhalides and transition-metal nitride halides have been reported as gate dielectrics in field-effect transistor (FET) applications. However, chalcogenide halides have been rarely explored as gate dielectrics. In this work, we systematically evaluated the potential of ScXY (X = S,Se,Te; Y = Cl,Br,I) monolayers as replacements for hBN, focusing on their stability, electronic properties, dielectric properties, and leakage current through first-principles calculations. Based on analyses of stability and band gap, we identified five monolayers, namely ScSY (Y = Cl,Br,I), ScSeBr, and ScSeI, which are easily exfoliable and exhibit both thermodynamic and dynamic stability, with large band gaps (>2.0 eV). These materials also exhibit favorable band offsets, high dielectric constants (ϵ∥0∼14.36-18.54 and ϵ⊥0∼3.25-4.35), high breakdown strength (0.99 - 1.54 MV/cm), and low leakage currents (<10-6 A cm-2), indicating their potential as gate dielectric materials. Notably, the ScSBr monolayer stands out as the most promising candidate among the five ScXY monolayers, owing to its highest breakdown strength (1.54 MV/cm), largest conduction band minimum (CBM) offset, and the lowest leakage current (<10-10 A cm-2). Our study offers valuable insights into the development of chalcogenide halide gate dielectrics for next-generation electronic devices.