Nonvolatile Control of Optical and Electronic Responses in Two-Dimensional MoS via Ferroelectric ScAlN Thin Films.

Wurtzite-structured ScAlN is a recently discovered ferroelectric material, and unique functionalities can emerge at the heterointerface between ScAlN and two-dimensional (2D) semiconductors, a territory that has yet to be fully explored. In this work, we report the controlled fabrication of inch-scale ScAlN thin films with high ferroelectric properties via reactive co-sputtering as well as the nonvolatile control of photoluminescence (PL) emission and electronic responses in 2D MoS by interfacing with ScAlN. The results show that as-grown ScAlN thin films are uniform at wafer scale (≥2 in.) and possess an ultrasmooth surface (≤1.7 Å), ultralow coercive field (≤0.04 V/nm), and out-of-plane polar axis. By interfacing monolayer MoS with ScAlN, we realize nonvolatile modulation of PL intensity and position in MoS, which is attributed to ScAlN's ferroelectric polarization-induced exciton-to-trion conversion, as evidenced by pizoresponse force microscopy and PL mapping analyses. Moreover, we fabricate high-performance ScAlN/2D MoS ferroelectric field-effect transistors, which exhibit a high current switching ratio (≥4.3 × 10) and an ultralow subthreshold swing (≤4.17 mV dec), exceeding most of the previously reported ScAlN/semiconductor devices. This study not only offers a cost-effective route to inch-scale fabrication of high-quality ScAlN films but also promotes the development of advanced optoelectronic devices based on III-nitride ferroelectric/2D heterostructures.