Owing to their exceptional properties, which are usually determined by the growth conditions, 2D transition metal dichalcogenides (TMDCs) offer numerous research directions for applications in the fields of spintronics, valleytronics, and optoelectronics. Here, we focus on the chemical vapor deposition (CVD) synthesis of WSe₂ (tungsten diselenide) nanoclusters/nanoflakes by using a liquid precursor for tungsten (ammonium metatungstate) on Si/SiO₂, fused silica, and sapphire substrates. Various WSe₂ clusters with different sizes, thicknesses, and geometries were analyzed by means of optical and atomic force microscopy (AFM) and Raman spectroscopy. The observed structures were mostly WSe₂ multilayers; however, monolayer formations were also found. They showed significant morphological differences, as well as wide nucleation density and size variations, possibly related to precursor/substrate surface interactions under the same CVD synthesis conditions. The largest WSe₂ domains with a lateral size of up to hundreds of micrometers were observed on sapphire, probably caused by a higher growth rate of singular nucleation sites. WSe₂ domains with irregular and triangular shapes were simultaneously identified on fused silica, whereas multilayered pyramidal WSe₂ structures dominated in the case of Si/SiO₂ substrates. The application of polarized Raman spectroscopy to precisely determine and differentiate the characteristic vibrational modes (${\mathrm{A}}_{1\mathrm{g}}$, ${\mathrm{E}}_{2\mathrm{g}}$, and $2\mathrm{L}\mathrm{A}\left(\mathrm{M}\right)$) enabled the unambiguous identification of 2D and/or multilayered WSe₂ formations with a high crystallinity level. The presented comparative analysis of samples prepared in relatively simple synthesis conditions (moderate working temperatures and ambient pressure) provides a base for further progress of the facile metatungstate CVD method and relevant opportunities for the exploration of 2D TMDC materials.

We report a two-step growth process of MoS₂ nanoflakes using a low-pressure chemical vapor deposition technique. In the first step, a MoS₂ layer was synthesized on a c-plane sapphire substrate. This layer was subsequently re-evaporated at a higher temperature to form mono- or few-layer MoS₂ flakes. As a result, the close proximity re-evaporation enabled the growth of pristine MoS₂ nanoflakes. Atomic force microscopy analysis confirmed the synthesis of nanoclusters/nanoflakes with lateral dimensions of over 10 μm and a flake height of approximately 1.3 nm, demonstrating bi-layer MoS₂, whereas transmission electron microscopy analysis revealed triangular MoS₂ nanoflakes, with a diffraction pattern proving the presence of single crystalline hexagonal MoS₂. Raman data revealed the typical modes of high-quality MoS₂ nanoflakes. Finally, we presented the photocurrent dependence of a MoS₂-based photoresist under illumination with light-emitting diode of 405 nm wavelength. The measured current–voltage dependence across various luminous flux outlined the sensitivity of MoS₂ to polarized light and thus opens further opportunities for applications in high-performance photodetectors with polarization sensitivity.

We report the synthesis of tungsten diselenide (WSe₂) flakes and continuous layers using an atmospheric pressure thermally assisted conversion (TAC) method, where the tungsten (W) layers were pre-deposited by a magnetron sputtering system onto fused silica substrates. Optical microscopy (OM) and atomic force microscopy (AFM) mapping predominantly revealed the formation of isolated flakes with different shapes, mainly concentrated near the substrate’s edges, which tended to form clusters and to further overlap to continuous layers, moving to the central part of the fused silica substrates. Raman spectroscopy and photoluminescence measurements confirmed the existence of atomically thin flakes and 2H-WSe₂ continuous layers. The measured current–voltage characteristics indicated Ohmic behavior under dark conditions and photo illumination. Finally, the demonstrated resistor-like behavior suggested unlimited prospects for WSe₂ integration into a variety of heterostructures.

Recently, low-dimensional structures in the form of bulk crystals and nanoflakes have received considerable interest due to their 2D unique functionality and promising applications in electronics, photonics, sensing devices and photovoltaic solar cells. As a result, remarkable efforts and modifications have been made for the synthesis process of crystalline material by the vapor transport technique. Here, an alternative concept of NbSe₂ crystal growth by the chemical vapor transport (CVT) technique using bromine as a vapor transport agent is presented and subsequently analyzed by X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS) spectroscopy. X-ray powder diffraction analysis revealed hexagonal 2H-NbSe₂ and 4H-NbSe₂ phases, and characteristic Raman and XPS spectra typical for crystalline NbSe₂ were obtained. The environmental sensitivity of the grown crystals is manifested by luminescence attributed to oxidized Nb at the samples’ surface.

This study reports the successful fabrication and characterization of two-dimensional (2D) vertical heterostructures composed of a semiconducting molybdenum disulfide (MoS₂) layer stacked with semimetallic platinum dichalcogenides (PtSe₂ and PtTe₂). The heterostructures were created using a versatile fabrication method that combines chemical vapor deposition (CVD) to grow high-quality MoS₂ nanolayers with thermally assisted conversion (TAC) for the synthesis of the Pt-based layers. The final MoS₂/PtSe₂ and MoS₂/PtTe₂ heterostructures were then assembled via a dry transfer process, ensuring high structural integrity. The quality and properties of these heterostructures were investigated using a range of advanced spectroscopic techniques. Raman spectroscopy confirmed the presence of characteristic vibrational modes for each material, validating successful formation. X-ray photoelectron spectroscopy (XPS) analysis further confirmed the elemental composition and oxidation states, though it also revealed the presence of elemental Pt⁰ and oxidized Te⁺⁴ in the PtTe₂ layer, suggesting an incomplete conversion. Importantly, the photoluminescence (PL) spectra showed a significant quenching effect, a clear sign of strong interlayer charge transfer, which is essential for optoelectronic applications. Finally, UV-Vis-NIR spectrophotometry demonstrated the combined optical properties of the stacked layers, with the Pt-based layers causing broadening and a blue-shift in the MoS₂ exciton peaks, indicating altered electronic and optical behavior. This research provides valuable insights into the synthesis and fundamental properties of MoS₂/PtX₂ heterostructures, highlighting their potential for next-generation electronic and optoelectronic devices.

The present study focuses on liquid-precursor-mediated chemical vapor deposition (under ambient pressure and moderate temperature range) of WSe₂ on sapphire using ammonium meta-tungstate and sodium cholate. The investigation provides additional results and information for the WSe₂ cluster formations on sapphire as an extension of our previous study, especially based on structural, chemical and morphological characterization of the observed largest and predominant polygonal WSe₂ domains whose lateral size can reach several hundreds of micrometers. In addition, highly symmetrical shapes were also observed. The Raman spectroscopy and atomic force microscopy identified the formation of both mono- and multilayered WSe₂. Moreover, the Raman spectrum analysis shows a complex peak structure with unusual splitting effects in the second-order modes marking strong activity of excitonic-resonance processes.