Transition metal dichalcogenides (TMDs) have attracted significant interest as one of the key materials in future electronics such as logic devices, optoelectrical devices, and wearable electronics. However, a complicated synthesis method and multistep processes for device fabrication pose major hurdles for their practical applications. Here, we introduce a direct and rapid method for layer-selective synthesis of MoS 2 and WS 2 structures in wafer-scale using a pulsed laser annealing system (λ = 1.06 μm, pulse duration ∼100 ps) in ambient conditions. The precursor layer of each TMD, which has at least 3 orders of magnitude higher absorption coefficient than those of neighboring layers, rigorously absorbed the incoming energy of the laser pulse and rapidly pyrolyzed in a few nanoseconds, enabling the generation of a MoS 2 or WS 2 layer without damaging the adjacent layers of SiO 2 or polymer substrate. Through experimental and theoretical studies, we establish the underlying principles of selective synthesis and optimize the laser annealing conditions, such as laser wavelength, output power, and scribing speed, under ambient condition. As a result, individual homostructures of patterned MoS 2 and WS 2 layers were directly synthesized on a 4 in. wafer. Moreover, a consecutive synthesis of the second layer on top of the first synthesized layer realized a vertically stacked WS 2 /MoS 2 heterojunction structure, which can be treated as a cornerstone of electronic devices. As a proof of concept, we demonstrated the behavior of a MoS 2 -based field-effect transistor, a skin-attachable motion sensor, and a MoS 2 /WS 2 -based heterojunction diode in this study. The ultrafast and selective synthesis of the TMDs suggests an approach to the large-area/mass production of functional heterostructure-based electronics.

Thin film fabrication is necessary to realize the device integration of organic–inorganic hybrid perovskites (OIHPs), and solution-based crystallization methods have been employed widely to this end. Despite the versatility of the solution approach, device fabrication using typical “top-down” lithography is generally incompatible with as-prepared OIHPs films because of the low stability of perovskites to polar solvents involved in the lithographic process. Moreover, solution-prepared perovskites usually exhibit irregular surface roughness, implying the existence of randomly oriented crystal domains with a large density of grain boundaries, which are ultimately detrimental to the material properties. Here, we report a patterning of CH3NH3PbI3 (MAPbI3) thin films using a photolithographically fabricated cross-linked copolymer template on Si or SiO2 substrates via a chemical vapor deposition (CVD) method. Perovskite patterning is accomplished by growing PbI2 precursor layers selectively on template patterns and subsequently converting to MAPbI3 using CH3NH3I (MAI) in the vapor phase. We confirm that [0001]-oriented PbI2 nanoplatelets nucleate primarily on a Si or SiO2 surface and grow by surface diffusion from a polymer surface. The MAPbI3 conversion process preserves the original pattern morphology through the vapor–solid intercalation of MAI. Prototype photodetector arrays based on MAPbI3 patterns are also demonstrated. Our results highlight the advantages of the CVD patterning of perovskite materials in large-scale production for a range of optoelectronic applications.

Here, we studied the triboelectric properties of structurally controlled laser-induced graphene (LIG) to clarify the key factors for improving the energy harvesting performance. With a facile defocusing method, the LIG...

A transparent and flexible film capable of shielding electromagnetic waves over a wide range of frequencies (X and K u bands, 8−18 GHz) is prepared. The electromagnetic wave shielding film is fabricated using the excellent transmittance, electrical conductivity, and thermal stability of indium tin oxide (ITO), a representative transparent conductive oxide. The inherent mechanical brittleness of oxide ceramics is overcome by adopting a nanobranched structure. In addition, mechanical stability is maintained even after repeated bending experiments (200 000 times). The produced transparent and flexible shielding film is applied to practical GHz devices (Wi-Fi and LTE devices), and signal sensitivity is confirmed to decrease. Therefore, it can be widely applied to various transparent and flexible electronic devices.