Thermodynamically guided synthesis of 3R-TaSe₂ nanocrystals and their superconducting behavior

Two-dimensional (2D) TaSe₂ has recently garnered significant attention due to its intrinsic physical properties, e.g., charge density wave (CDW) states, Mott insulator transitions, and superconductivity. In this study, we optimized the synthesis conditions for preparing highly crystalline 3R-TaSe₂ using a chemical vapor transport (CVT) approach. We systematically investigated the influence of substrate type on the morphology of the resulting nanocrystals (NCs) and elucidated the underlying growth mechanisms. The NCs were grown on various substrates, including SiO₂/Si, c-sapphire (0001), and mica, under optimal conditions. The deposited crystals were characterized using various techniques, including optical microscopy (OM), atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and high-resolution transmission electron microscopy (HRTEM). In addition, magneto-transport measurements were carried out. Of particular interest, the prepared 3R-TaSe₂ NCs showed a signature of CDWs at around 100 K and an onset of superconductivity below 2.2 K. Such highly crystalline NCs are interesting for fundamental research of properties such as CDW phenomena and superconductivity at the nanoscale. This work provides insights into substrate-mediated growth and paves the way for advancing the knowledge of 2D TaSe₂ materials for potential applications in next-generation nanodevices.