UC Riverside

The ability to grow crystals of desired dimensions is an important aspect of the design of new functional materials. The crystals grown in two dimensions enable successful and efficient modification of a wide range of physical, electronic and structural properties tailored for smaller and more efficient electronics, optoelectronics, valleytronics, and spintronic applications. The control of phases in crystals is also an additional element in the design of functional materials. Two-dimensional (2D) atomic crystals can crystallize in a variety of crystal phases, which possess distinct properties. Therefore, identifying approaches for controlling dimension and crystal phase is essential for tuning the properties of 2D materials to specific applications. Herein, various unique methods of producing 2D atomic layered metal chalcogenide crystals (LMCs) including growth of group VI transition metal dichalcogenides (TMDs) by chalcogenization of pre-deposited metal-containing precursors, and phase-engineered growth of group IV LMCs by vapor-phase reaction of metal oxide and chalcogen powders are demonstrated. Scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), optical microscopy, Raman spectroscopy, photoluminescence (PL) spectroscopy, ultraviolet photoelectron spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), and X-ray diffraction (XRD) are all notable experimental techniques used to characterize these various materials. The experimental results are corroborated by density functional theory (DFT) calculations.