Abstract:

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) exhibit diverse structures, encompassing a broad spectrum of electronic types ranging from metal, semiconductor, to insulator and topological insulator. They hold immense potential for both Moore and more-than-Moore device applications. Among them, manganese telluride (MnTe), an emerging nonlayered 2D material, has garnered considerable attention due to its exceptional properties and significant application potential in next-generation electronic and optoelectronic devices. However, the controllable synthesis of ultra-thin 2D MnTe remains a great challenge, which hindering the comprehensive exploration of its fundamental properties and potential applications. In this study, we present the synthesis of large-area MnTe nanosheets through chemical vapor deposition growth, showcasing its thickness-dependent properties and device applications. By increasing the growth temperature from 500 to 750 ℃, the MnTe nanosheets' thickness transitions from thin-layer to a thick flake, the domain size increases from 10 to 125 μm, the morphology changes from triangle to hexagon, culminating in a highly symmetrical round shape. Structural characterization and second harmonic generation measurements reveal that the obtained MnTe nanosheets exhibit high crystallization quality and superior second-order optical nonlinearity. The field effect transistor (FET) constructed with thin-layer MnTe demonstrates a p-type semiconductor characteristic, transitioning to a semimetal feature as the thickness increases to a thick flake. Leveraging these thickness-dependent electrical conduction transition features, we explore diverse applications of MnTe with varying thicknesses. The semiconductive thin-layer MnTe, serving as the photosensitive channel in a device, achieves superior photoresponse, showcasing considerable potential for photodetection appliations. The semimetallic thick-layer MnTe, acting as the contact electrode in a MoS₂ FET, significantly enhances device performance, with carrier mobility increasing from 12.76 cm²∙V⁻¹∙s⁻¹ (Au contact) to 47.34 cm²∙V⁻¹∙s⁻¹ (MnTe contact). This work lays the foundation for the controllable synthesis of nonlayered 2D MnTe and provides insights into its prospective development for constructing innovative electronic and optoelectronic devices.

Key words: 2D materials, MnTe, Chemical vapor deposition, Field effect transistor, Photodetector, Contact electrode