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Large-scale, high-quality growth of transition metal dichalcogenides (TMD) of controlled thickness is paramount for many applications in opto- and microelectronics. This paper describes the direct growth of well-controlled large area molybdenum disulfide (MoS 2 ) on Si/SiO 2 substrates by direct liquid injection pulsed-pressure metal-organic chemical vapor deposition (DLI-PP-MOCVD) using low-toxicity precursors. It is shown that control of the deposited thickness can be achieved by carefully tuning the amount of molybdenum precursor evaporated and that continuous layers are routinely obtained. Homogeneity and reproducibility have also been examined, as well as the average size of the grains. When targeting monolayer thickness, the MoS 2 showed near stoichiometry (S/Mo = 1.93-1.95), low roughness and high photoluminescence (PL) quantum yield, equivalent to exfoliated monolayers and CVD MoS 2 grown on the same substrates.

Active commuting (AC) may have the potential to prevent the incidence of cardiovascular disease (CVD). However, the evidence for a correlation between AC and the risk of CVD remains uncertain. The current study thoroughly and qualitatively summarized research on the relationship between AC and the risk of CVD disease. From conception through December 2022, researchers explored four databases (PubMed, PEDro, Cochrane, and Bibliothèque Nationale of Luxembourg [BnL]) for observational studies. The initial findings of the search yielded 1042 references. This systematic review includes five papers with 491,352 participants between 16 and 85 years old, with 5 to 20 years of follow-up period. The exposure variable was the mode of transportation used to commute on a typical day (walking, cycling, mixed mode, driving, or taking public transportation). The primary outcome measures were incident CVD, fatal and non-fatal (e.g., ischemic heart disease (IHD), ischemic stroke (IS), hemorrhagic stroke (HS) events, and coronary heart disease (CHD). Despite methodological variability, the current evidence supports AC as a preventive measure for the development of CVD. Future research is needed to standardize methodologies and promote policies for public health and environmental sustainability.

Raman spectroscopy is a widely used technique to characterize nanomaterials because of its convenience, non-destructiveness, and sensitivity to materials change. The primary purpose of this work is to determine via Raman spectroscopy the average thickness of MoS 2 thin films synthesized by direct liquid injection pulsed-pressure chemical vapor deposition (DLI-PP-CVD). Such samples are constituted of nanoflakes (with a lateral size of typically 50 nm, i.e., well below the laser spot size), with possibly a distribution of thicknesses and twist angles between stacked layers. As an essential preliminary, we first reassess the applicability of different Raman criteria to determine the thicknesses (or layer number, N ) of MoS 2 flakes from measurements performed on reference samples, namely well-characterized mechanically exfoliated or standard chemical vapor deposition MoS 2 large flakes deposited on 90 ± 6 nm SiO 2 on Si substrates. Then, we discuss the applicability of the same criteria for significantly different DLI-PP-CVD MoS 2 samples with average thicknesses ranging from sub-monolayer up to three layers. Finally, an original procedure based on the measurement of the intensity of the layer breathing modes is proposed to evaluate the surface coverage for each N (i.e., the ratio between the surface covered by exactly N layers and the total surface) in DLI-PP-CVD MoS 2 samples., (Copyright © 2024, Wasem Klein et al.)

We report on transport measurements in monolayer MoS 2 devices, close to the bottom of the conduction band edge. These devices were annealed in situ before electrical measurements. This allows us to obtain good ohmic contacts at low temperatures, and to measure precisely the conductivity and mobility via four-probe measurements. The measured effective mobility up to μ eff = 180 cm 2 V -1 s -1 is among the largest obtained in CVD-grown MoS 2 monolayer devices. These measurements show that electronic transport is of the insulating type for σ ≤ 1.4 e 2 / h and n ≤ 1.7 × 10 12 cm -2 , and a crossover to a metallic regime is observed above those values. In the insulating regime, thermally activated transport dominates at high temperature ( T > 120 K). At lower temperatures, conductivity is driven by Efros-Schklovkii variable range hopping in all measured devices, with a universal and constant hopping prefactor, that is a clear indication that hopping is not phonon-mediated. At higher carrier density, and high temperature, the conductivity is well modeled by the Boltzmann equation for a non-interacting Fermi gas, taking into account both phonon and impurity scatterings. Finally, even if this apparent metal-insulator transition can be explained by phonon-related phenomena at high temperature, the possibility of a genuine 2D MIT cannot be ruled out, as we can observe a clear power-law diverging localization length close to the transition, and a one-parameter scaling can be realized., (© 2023 IOP Publishing Ltd.)

Hybrid van der Waals heterostructures made of 2D materials and organic molecules exploit the high sensitivity of 2D materials to all interfacial modifications and the inherent versatility of the organic compounds. In this study, we are interested in the quinoidal zwitterion/MoS 2 hybrid system in which organic crystals are grown by epitaxy on the MoS 2 surface and reorganize in another polymorph after thermal annealing. By means of field-effect transistor measurements recorded in situ all along the process, atomic force microscopy and density functional theory calculations we demonstrate that the charge transfer between quinoidal zwitterions and MoS 2 strongly depends on the conformation of the molecular film. Remarkably, both the field effect mobility and the current modulation depth of the transistors remain unchanged which opens up promising prospects for efficient devices based on this hybrid system. We also show that MoS 2 transistors enable fast and accurate detection of structural modifications that occur during phases transitions of the organic layer. This work highlights that MoS 2 transistors are remarkable tools for on-chip detection of molecular events occurring at the nanoscale, which paves the way for the investigation of other dynamical systems., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)