Heterogeneous Electronic and Photonic Devices Based on Monolayer Ternary Telluride Core/Shell Structures

Abstract

Device engineering based on the tunable electronic properties of ternary transition metal dichalcogenides has recently gained widespread research interest. In this work, monolayer ternary telluride core/shell structures are synthesized using a one‐step chemical vapor deposition process with rapid cooling. The core region is the tellurium‐rich WSe2−2xTe2x alloy, while the shell is the tellurium‐poor WSe2−2yTe2y alloy. The bandgap of the material is ≈1.45 eV in the core region and ≈1.57 eV in the shell region. The lateral gradient of the bandgap across the monolayer heterostructure allows for the fabrication of heterogeneous transistors and photodetectors. The difference in work function between the core and shell regions leads to a built‐in electric field at the heterojunction. As a result, heterogeneous transistors demonstrate a unidirectional conduction and strong photovoltaic effect. The bandgap gradient and high mobility of the ternary telluride core/shell structures provide a unique material platform for novel electronic and photonic devices.

Maneuvering Tellurium Chemistry to Design Metal–Telluride Heterostructures for Diverse Applications

“…Additionally, metal–tellurides have a shorter bandgap and absorb light at longer wavelength; hence, their applications in solar-energy-harvesting devices is gradually gaining momentum. The structural variety and distinct properties of Te-based nanocrystals prompted researchers to design and generate several intriguing metal–telluride heterostructures with unique properties and enhanced performances in their technological applications. − Among these, several disk or dot on Te nanorod, ,,− twin, core/shell, − and other complex metal–telluride heterostructures − have been synthesized and explored for various applications. ,− ,, …”

“…Research on heterostructure nanocrystals, in general, has attracted greater attention in the past few decades due to their broad range of applications in several areas of nanoscience, including electronics, magnetism, catalysis, self-assembly, optics, energy, biology, and so on. The advancement of the synthetic methodology enabled precise control over the shape, size, and morphology of these heterostructures, thus opening a pandora’s box of opportunities and challenges to investigate the structure–property relationships and their related applications. ,,− Being low bandgap semiconductors, the Te-based heterostructures are considered to have potential applications in high-efficiency energy devices such as electrocatalysis, photodetectors, and photovoltaics, to name a few. However, unlike sulfides and selenides, there are fewer reports that discuss the electrocatalytic behavior of metal–telluride heterostructures.…”

“…Recently, Zhu and co-workers synthesized monolayer WSe 2–2 x Te 2 x /WSe 2–2 y Te 2 y core/shell heterostructures following a single-step chemical vapor deposition process . The core consists of the tellurium-rich WSe 2–2 x Te 2 x alloy, while the shell region consists of the tellurium-poor WSe 2–2 y Te 2 y alloy.…”

“…(a) Schematic of the growth process of monolayer WSe 2–2 x Te 2 x /WSe 2–2 y Te 2 y core/shell heterostructures, (b) different transistor behaviors in the core and shell regions of the heterostructures;, (c) I D – V D output characteristics with variations in the applied gate voltage V G of an EDLT-capped core/shell PbTe/PbS nanocrystal assembly for both p-channel (blue) and n-channel (red) operations (the inset shows a schematic of the EDLT circuit), (d) comparison of the logarithmically scaled I D – V ref transfer characteristics of EDLTs using PbTe/PbS (red) and the core PbTe nanocrystals, (d′) corresponding transfer characteristics plotted on a linear scale of the conductivity, (e) schematic circuit diagram illustrating the Seebeck effect, (f) ZT of the PbTe–Ag 2 Te nanocomposite compared with that of the Ag 2 Te nanocomposite, and (g) scheme depicting the applicability of Au/ZnTe core/shell nanoparticles in chemotherapeutic drugs for targeted drug delivery and bioimaging. Panels (a and b) were reprinted with permission from ref . Copyright 2020 Wiley-VCH.…”

Magnetic Nanosheets via Chemical Exfoliation of K2xMnxSn1–xS2

“…Layered transition metal dichalcogenides (TMDs) stand out as an interesting family, as they adopt crystal structures in which adjacent layers are merely held together by weak van der Waals (vdW) interactions. In fact, many groups have reported successful exfoliation of TMDs with a wide range of methods. − In the early stages of Li-ion battery development, TMDs were researched as potential cathodes due to their layered structures. For example, TiS 2 was among the first materials used in Li-ion batteries, before John Goodenough discovered much more successful cathodes such as LiCoO 2 and LiFePO 4 . , TMDs are considered to be great candidates for a large variety of other applications as well, including transistors, emitters and detectors, hydrogen evolution reaction (HER) catalysts, and sensing devices. − As a low cost and nontoxic material, SnS 2 is considered a promising TMD for realizing many of the applications mentioned above. ,− SnS 2 adopts a CdI 2 -type structure (space group P 3̅ m ), possesses a band gap of 2.1–2.3 eV, and has high surface activity and sensitivity.…”