Natural Layered Phlogopite Dielectric for Ultrathin Two-Dimensional Optoelectronics.

Pucher, Thomas; Hernandez-Ruiz, Julia; Tajuelo-Castilla, Guillermo; Martín-Gago, José Ángel; Munuera, Carmen; Castellanos-Gomez, Andres · ACS Nano · 2025

basic_science · Level V

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Abstract

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<sup>-1</sup>) of phlogopite enable transistors with subthreshold swings down to 100 mV dec<sup>-1</sup>, 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 (MoS<sub>2</sub>) and phlogopite exhibit responsivities up to 3.3 × 10<sup>4</sup> AW<sup>-1</sup> and detectivities close to 10<sup>10</sup> Jones, surpassing devices based on conventional gate insulators. We further demonstrate the versatility of this natural dielectric by integrating phlogopite/MoS<sub>2</sub> 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.