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Description
Gate dielectrics are a central materials challenge for reliable 2D electronics, where device behaviour is strongly governed by interfacial quality and high-field stability. While hexagonal boron nitride (hBN) is widely used as the benchmark van der Waals dielectric, layered silicates offer an attractive alternative due to their compositional versatility, abundance, and robustness. Here, we present a comparative study of synthetic fluorophlogopite mica (FPh) and hBN as gate dielectrics in MoS₂-based 2D devices.
By combining structural characterization with electrical measurements on capacitor and transistor geometries, we show that FPh sustains markedly higher breakdown fields than hBN, reaching values up to about 10 MV/cm and yielding Weibull statistics consistent with a substantially improved dielectric strength. At moderate gate fields, FPh-based field-effect transistors remain comparable to hBN devices in key figures of merit such as transfer characteristics, threshold voltage, subthreshold swing, and transconductance-based mobility. Dual-gate measurements further give a dielectric constant of about 7 for FPh.
At higher applied fields, however, FPh exhibits an additional functionality absent in hBN: a pronounced and continuously increasing hysteresis that can be tuned by the maximum gate field. We demonstrate field-induced writing of distinct conductance states around zero gate bias and analyse their temporal relaxation. Temperature-dependent hysteresis, Kelvin probe force microscopy, and cross-sectional compositional analysis indicate a mixed mechanism involving both charge trapping and mobile ionic species. These results identify fluorophlogopite as a promising van der Waals dielectric that combines competitive low-field transistor operation with high-field memory-like functionality.