Ripple is a common deformation in two-dimensional materials due to localized strain, which is expected to greatly influence the physical properties. The effects of the ripple deformation in the MoS ₂ layer on their physics, however, are rarely addressed experimentally. We here grow atomically thin MoS ₂ nanostructures by employing a vapor phase deposition method without any catalyst and observed the ripples in MoS ₂ nanostructures. The MoS ₂ ripples exhibit quasi-periodical ripple structures in the MoS ₂ surface. The heights of the ripples vary from several angstroms to tens of nanometers and the wavelength is in the range of several hundred nanometers. The growth mechanism of rippled MoS ₂ nanostructures is elucidated. We have also simultaneously investigated the electrostatic properties of MoS ₂ ripples by using Kelvin probe force microscopy, which shows inhomogeneous surface potential and charge distributions for MoS ₂ ripple nanostructures with different local strains.

Atomically thin transition metal dichalcogenides (TMDCs) have drawn much interest for their promising applications in electronic, optoelectronic, valleytronic and sensing fields. Controlled growth of large-scale and high-quality TMDC nanostructures is highly desirable but remains challenging. In the present work, large-scale monolayer, bilayer and few-layer MoSe ₂ films have been controllably synthesized by ambient pressure chemical vapor deposition (APCVD). Hydrogen flow rate, growth temperature as well as selenium–metal flux ratio have been systematically investigated, which were demonstrated to play a key role in the synthesis of MoSe ₂ nanostructures. We have also reported the successful growth of MoSe ₂ nanoribbons with controlled width and length on diverse substrates by APCVD with the assistance of sodium chloride and corresponding growth mechanism was proposed. Our findings highlight the prospects for the controlled growth of novel 1D and 2D TMDC nanostructures for nanoelectronic devices and the development of mixed-dimensional heterostructures.

As one of two-dimensional (2D) semiconductor materials, transition metal dichalcogenides (TMDs) have sparked enormous potential in next-generation electronics due to their unique and excellent physical, electronic and optical properties. Controllable growth of wafer-scale 2D TMDs is essential to realize the various high-end applications of TMDs, while it remains challenging. Herein, 2 inch 2D WS₂ films were successfully synthesized by ambient pressure chemical vapor deposition based on substrate engineering and space-confined strategies. WS₂ nucleation density can be effectively modulated depending on the annealing conditions of sapphire substrate. The thickness of WS₂ films can be controllably fabricated by adjusting the space-confined height. Moreover, our strategies are demonstrated to be universal for the growth of other 2D TMD semiconductors. WS₂-based photodetectors with different thicknesses were systematically investigated. Monolayer WS₂ photodetector displays large responsivity of 0.355 A W⁻¹ and high specific detectivity of 1.48 × 10¹¹ Jones. Multilayer WS₂ device exhibits negative self-powered photoresponse. Our work provides a new route for the synthesis of wafer-scale 2D TMD materials, paving the way for high performance integrated optoelectronic devices.