Electrical spectroscopy of defect states and their hybridization in monolayer MoS.

Defects in solids are unavoidable and can create complex electronic states that can significantly influence the electrical and optical properties of semiconductors. With the rapid progress in the integration of 2D semiconductors in practical devices, it is imperative to understand and characterize the influence of defects in this class of materials. Here, we examine the electrical response of defect filling and emission using deep level transient spectroscopy (DLTS) and reveal defect states and their hybridization in a monolayer MOCVD-grown material deposited on CMOS-compatible substrates.

Wafer-scale MoS with water-vapor assisted showerhead MOCVD.

Among numerous thin film synthesis methods, metalorganic chemical vapor deposition performed in a showerhead reactor is the most promising one for broad use in scalable and commercially adaptable two-dimensional material synthesis processes. Adapting the most efficient monolayer growth methodologies from tube-furnace systems to vertical-showerhead geometries allows us to overcome the intrinsic process limitations and improve the overall monolayer yield quality. Here, we demonstrate large-area, monolayer molybdenum disulphide growth by combining gas-phase precursor supply with unique tube-furnace approaches of utilizing sodium molybdate pre-seeding solution spincoated on a substrate along with water vapor added during the growth step.

Superconducting 2D NbS Grown Epitaxially by Chemical Vapor Deposition.

Metallic two-dimensional (2D) transition metal dichalcogenides (TMDCs) are attracting great attention because of their interesting low-temperature properties such as superconductivity, magnetism, and charge density waves (CDW). However, further studies and practical applications are being slowed down by difficulties in synthesizing high-quality materials with a large grain size and well-determined thickness. In this work, we demonstrate epitaxial chemical vapor deposition (CVD) growth of 2D NbS crystals on a sapphire substrate, with a thickness-dependent structural phase transition.

One-step vapour phase growth of two-dimensional formamidinium-based perovskite and its hot carrier dynamics.

Formamidinum lead iodide perovskite is one of the most promising materials for application in solar cells due to its narrow band gap and higher thermal stability. In this work, we demonstrate the facile synthesis of square-shaped formamidinium lead iodide single crystals on indium tin oxide (ITO) substrates using a one-step vapour phase deposition method. Formamidinium lead iodide-based two-dimensional layered perovskite crystals were successfully synthesized by controlling the deposition conditions.

Scanning Moiré Fringe Method: A Superior Approach to Perceive Defects, Interfaces, and Distortion in 2D Materials.

Scanning moiré fringe (SMF) is a widely utilized technique for the precise measurement of the strain field in semiconductor transistors and heterointerfaces. With the growing challenges of traditional chip scaling, two-dimensional (2D) materials turn out to be ideal candidates for incorporation into semiconductor devices. Therefore, a method to efficiently locate defects and grain boundaries in 2D materials is highly essential.

Vapor Phase Selective Growth of Two-Dimensional Perovskite/WS Heterostructures for Optoelectronic Applications.

Organic-inorganic hybrid perovskites have attracted increased interest owing to their exceptional optoelectronic properties and promising applications. Monolayers of transition metal dichalcogenides (TMDCs), such as tungsten disulfide (WS), are also intriguing because of their unique optoelectronic properties and their atomically thin and flexible structures. Therefore, the combination of these different types of materials is very attractive in terms of fundamental science of interface interaction, as well as for the realization of ultrathin optoelectronic devices with high performance.

Chemically Tuned p- and n-Type WSe Monolayers with High Carrier Mobility for Advanced Electronics.

Monolayers of transition metal dichalcogenides (TMDCs) have attracted a great interest for post-silicon electronics and photonics due to their high carrier mobility, tunable bandgap, and atom-thick 2D structure. With the analogy to conventional silicon electronics, establishing a method to convert TMDC to p- and n-type semiconductors is essential for various device applications, such as complementary metal-oxide-semiconductor (CMOS) circuits and photovoltaics. Here, a successful control of the electrical polarity of monolayer WSe is demonstrated by chemical doping.

van der Waals interaction-induced photoluminescence weakening and multilayer growth in epitaxially aligned WS.

Recently, transition metal dichalcogenides (TMDCs) have attracted great interest due to their unique electronic and optical properties. Chemical vapor deposition (CVD) has been regarded as the most promising method for the synthesis of large-area TMDCs with high reproducibility. Having similar hexagonal crystal structures with many TMDCs, c-plane sapphire is commonly used as a growth substrate in CVD.

Surface-Mediated Aligned Growth of Monolayer MoS and In-Plane Heterostructures with Graphene on Sapphire.

Aligned growth of transition metal dichalcogenides and related two-dimensional (2D) materials is essential for the synthesis of high-quality 2D films due to effective stitching of merging grains. Here, we demonstrate the controlled growth of highly aligned molybdenum disulfide (MoS) on c-plane sapphire with two distinct orientations, which are highly controlled by tuning sulfur concentration. We found that the size of the aligned MoS grains is smaller and their photoluminescence is weaker as compared with those of the randomly oriented grains, signifying enhanced MoS-substrate interaction in the aligned grains.