Natural Layered Phlogopite Dielectric for Ultrathin Two-Dimensional Optoelectronics

The integration of high-dielectric-constant (high-κ) materials with two-dimensional (2D) semiconductors is promising to overcome performance limitations and reach their full theoretical potential. Here, we show that naturally occurring phlogopite mica, exfoliated into ultrathin flakes, can serve as a robust high-κ dielectric layer for transition metal dichalcogenide-based 2D electronics and optoelectronics. The wide band gap (∼4.8 eV), high dielectric constant (∼11), and large breakdown field (>10 MV cm^–1) of phlogopite enable transistors with subthreshold swings down to 100 mV dec^–1, minimal hysteresis (∼30–60 mV), and interface trap densities comparable to those of state-of-the-art oxide dielectrics. Moreover, phototransistors built upon monolayer molybdenum disulfide (MoS₂) and phlogopite exhibit responsivities up to 3.3 × 10⁴ AW^–1 and detectivities close to 10¹⁰ Jones, surpassing devices based on conventional gate insulators. We further demonstrate the versatility of this natural dielectric by integrating phlogopite/MoS₂ heterostructures into NMOS inverters, showcasing robust voltage gains and low-voltage operation. Our findings establish phlogopite as a promising, earth-abundant dielectric for next-generation 2D transistor technologies and high-performance photodetection.