Structure and Optical Properties of Some Layered Two-Dimensional Transition- Metal Dichalcogenides: Molybdenum Disulfide, Molybdenum Diselenide, and Tungsten Diselenide

This paper presents a systematic study of intrinsic characteristics of layered two-dimensional transitionmetal dichalcogenides, with a focus on molybdenum disulfide, molybdenum diselenide, and tungsten diselenide. Recent advances in high-resolution transmission electron microscopy (HRTEM) have made atomic-resolution imaging possible, thus enabling one to closely examine real and reciprocal space structures of two-dimensional materials. Our HRTEM micrographs, for example, confirm the expected hexagonal structure of the materials. Furthermore, lattice constant values with resolution on the order of tenths of angstroms could be extracted from the micrographs. Raman and photoluminescence spectroscopies are used to investigate the optical characteristics of the materials. These measurements provide insight into the properties of this class of materials, and their potential use in promising applications in electronic and photonic devices [1-5].