Lateral heterostructures of dissimilar monolayer transition metal dichalcogenides provide great opportunities to build 1D in‐plane p–n junctions for sub‐nanometer thin low‐power electronic, optoelectronic, optical, and sensing devices. Electronic and optoelectronic applications of such p–n junction devices fabricated using a scalable one‐pot chemical vapor deposition process yielding MoSe2‐WSe2 lateral heterostructures are reported here. The growth of the monolayer lateral heterostructures is achieved by in situ controlling the partial pressures of the oxide precursors by a two‐step heating protocol. The grown lateral heterostructures are characterized structurally and optically using optical microscopy, Raman spectroscopy/microscopy, and photoluminescence spectroscopy/microscopy. High‐resolution transmission electron microscopy further confirms the high‐quality 1D boundary between MoSe2 and WSe2 in the lateral heterostructure. p–n junction devices are fabricated from these lateral heterostructures and their applicability as rectifiers, solar cells, self‐powered photovoltaic photodetectors, ambipolar transistors, and electroluminescent light emitters are demonstrated.

The coupling of two-dimensional materials with optical metasurfaces is a promising avenue to enhance the advantageous properties of both platforms. Here we integrate an ultrathin monolayer of the transition metal dichalcogenide (TMD) MoS2, grown by chemical-vapor deposition, with a silicon metasurface, to obtain a hybrid system with enhanced nonlinear response. To this end, we utilize a metasurface exhibiting resonances with high quality factors, which provides increased optical fields. Using the nonlinearity of the TMD monolayer, these resonantly enhanced fields enable more efficient nonlinear frequency conversion. In particular, we experimentally observe an enhanced efficiency of second-harmonic generation in our hybrid structure. By comparing second-harmonic generation using different photonic resonances, we furthermore identify optimized conditions for the spatial distribution of the local optical fields to maximize the nonlinear response. Our results enable the precise design of hybrid structures consisting from TMDs and metasurfaces for future applications.

Silica-based optical fibres are a workhorse of nonlinear optics, providing ready access to a range of nonlinear phenomena including solitons and self-phase modulation. However, they have one fundamental limitation: due to the amorphous nature of silica, they do not exhibit second-order nonlinearity, except for negligible contributions from surfaces. Here we demonstrate second-harmonic generation in functionalized optical fibres by using a monolayer of highly nonlinear MoS2 directly grown on the fibre’s core. The MoS2-functionalized fibre exhibits a second-order susceptibility (χ(2)) value of 44 pm V–1 and a second-harmonic generation conversion efficiency of 0.2 × 10–3 m−2 W−1. This approach is scalable and can be generalized to other transition metal dichalcogenides and a wide range of waveguide systems. Our results demonstrate a new approach towards efficient in-fibre second-harmonic generation sources and may establish a platform for χ(2)-based nonlinear fibre optics, optoelectronics, photonics platforms, integrated optical architectures and active fibre networks.

Van der Waals (vdW) heterostructures composing of organic molecules with inorganic 2D crystals open the door to fabricate various promising hybrid devices. Here, a fully ordered organic self-assembled monolayer (SAM) to construct hybrid organic-inorganic vdW heterojunction phototransistors for highly sensitive light detection is used. The heterojunctions, formed by layering MoS 2 monolayer crystals onto organic [12-(benzo[b]benzo[4,5] thieno[2,3-d]thiophen-2-yl)dodecyl)]phosphonic acid SAM, are characterized by Raman and photoluminescence spectroscopy as well as Kelvin probe force microscopy. Remarkably, this vdW heterojunction transistor exhibits a superior photoresponsivity of 475 A W −1 and enhanced external quantum efficiency of 1.45 × 10 5 %, as well as an extremely low dark photocurrent in the pA range. This work demonstrates that hybridizing SAM with 2D materials can be a promising strategy for fabricating diversified optoelectronic devices with unique properties.

We studied the energy-level alignment at interfaces between various transition-metal dichalcogenide (TMD) monolayers, MoS 2 , MoSe 2 , WS 2 , and WSe 2 , and metal electrodes with different work functions (WFs). TMDs were deposited on SiO 2 /silicon wafers by chemical vapor deposition and transferred to Al and Au substrates, with significantly different WFs to identify the metal–semiconductor junction behavior: oxide-terminated Al (natural oxidation) and Au (UV–ozone oxidation) with a WF difference of 0.8 eV. Kelvin probe force microscopy was employed for this study, based on which electronic band diagrams for each case were determined. We observed the Fermi-level pinning for MoS 2 , while WSe 2 /metal junctions behaved according to the Schottky–Mott limit. WS 2 and MoSe 2 exhibited intermediate behavior.