MXenes combine distinctive properties, including high electrical conductivity, high thermal conductivity, and efficient absorption of electromagnetic waves, which allow them to be utilized in various applications such as electrical energy storage, sensors, and functional composites. This study aims to grow thin and large area Mo2C flakes in a controlled manner by using chemical vapor deposition, avoiding surface functionalization, and limited lateral dimensions. Herein, we investigate the effects of CH4 flow, the precursor/catalyst (Mo/Cu) ratio, and flow rates of carrier gas on the growth of two-dimensional Mo2C structures. This study examines the effects of the precursor/catalyst (Mo/Cu) ratio and flow rates of carrier gas on the growth of Mo2C structures. Our results show that when the flow rates of CH4, catalyst/precursor (Cu/Mo) ratio, and carrier gas (N2/H2) ratio are varied, we can control both thickness (from 7 to 145 nm) and coverage of the substrate surface (from 11% to 68%) of the Mo2C flakes. Therefore, this study reveals that it is possible to realize centimeter-scale surface coverage and controllable thicknesses by adjusting the process parameters. The deposited films and flakes are analyzed by optical microscopy, atomic force microscopy, and Raman scattering spectroscopy techniques. The Raman spectra are also compared with the theoretical calculations using density functional theory. Overall, the present work is expected to provide a significant impact for utilization of MXenes in various applications.

Two-dimensional (2D) monolayer transition metal dichalcogenides (TMDs) show extra-ordinary properties compared to their bulk forms, which has inspired a large number of researchers to investigate these materials recently. Design and fabrication of different combinations of 2D TMDs layers can allow for high-performance and novel heterostructure-based devices, of which the performance will depend also on their thermal properties. On the other hand, the temperature-dependent behavior of such heterolayers and their interaction at different temperatures is still not comprehensively studied in a wide temperature range. In this work, we have performed a systematical temperature-dependent (83 K—483 K) Raman spectroscopic analysis of the MoS2/MoSe2 van der Waals (vdW) heterostructures and discussed their stability. After the transfer process of the MoS2 monolayers onto the MoSe2/SiO2/Si, we annealed the samples, which is a commonly used process to increase the crystallinity. Associatively, the thermal annealing process leads to a decrease in the thermal coefficients of the E1 2g and A1g modes of MoS2 and MoSe2 monolayers. Our study shows that the peak positions of the Raman modes in the heterostructures redshift with an increase in temperature. Furthermore, the full width at half maximum (FWHM) of the E1 2g and A1g modes of the layers broaden at higher temperatures. This phenomenon is attributed to increasing phonon–phonon interactions and thermal expansion effects with the ascending temperature. To the best of our knowledge, for the first time, temperature-dependent Raman analysis of MoS2/MoSe2 vdW heterostructures before and after annealing are carried out; and peak positions, FWHMs, and thermal coefficients of the layers are extracted. We do not observe any deformation in the heterobilayer structure even at very low (83 K) or very high temperatures (483 K). This is the first step to confirm the durability of the MoS2/MoSe2 heterolayered devices under extreme temperatures by studying their thermal properties.

Two-dimensional (2D) materials such as transition metal dichalcogenides (TMDs) are prominent candidates to be utilized in integrated circuits. However, growing uniform and large-area 2D materials, specifically monolayers, that can be used in electronic component production is still one of the main challenges for these 2D materials to be incorporated in integrated circuits or other active device applications. The aim of this study is to demonstrate a practical and reliable MATLAB computational method, which calculates the ratio of the chemical vapor deposited monolayers to the whole substrate surface and the maximum area of the deposited flakes. In this study, we used the K-means clustering method to calculate surface coverage where we obtained accuracy of ~96% for the simple test images (single star and hexagonal shapes). For the multi-numbered and distributed shapes example, we achieved higher accuracy of ~98%. We also realized calculation of each flake area with ~99% accuracy indicating the flake with the maximum area. The practical calculation of the surface coverage ratio and flake size will allow for easy identification of the effects of the process parameters during novel material growth, which will pave way for future optoelectronic and electronic devices.

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