Utilization of Powder X-ray Diffraction (XRD) for Stoichiometric and Structural Characterization of Molybdenum Dichalcogenide Crystals Grown via Chemical Vapor Transport

This study explores the utilization of Powder X-ray Diffraction (XRD) as a reliable technique for confirming the stoichiometry and structural characteristics of molybdenum dichalcogenide (MoX₂; X = S, Se) single crystals grown via the Chemical Vapour Transport (CVT) technique. Employing high-purity elemental precursors and iodine as a transport agent, crystals were synthesized under carefully controlled thermal gradients. XRD measurements were conducted to assess crystallinity, lattice parameters, and phase purity. Rietveld refinement of diffraction patterns confirmed the 2H phase structure and revealed minor shifts indicating possible chalcogen vacancies. Complementary EDAX analyses validated the stoichiometric ratios. The synergy of powder XRD and CVT provides a robust method for producing and characterizing high-quality layered MoX₂ crystals for optoelectronic and pressure-dependent applications. Unlike conventional melt-growth or mechanical exfoliation techniques, the CVT method demonstrated here enables superior phase purity and tunable stoichiometry with high crystallographic uniformity, essential for reproducible device fabrication. Major Findings: High-quality MoS₂ and MoSe₂ single crystals were synthesized via CVT, exhibiting 2H-phase purity, consistent lattice constants, and low microstrain. XRD and Rietveld refinement confirmed superior crystallinity, while EDAX validated stoichiometry (Mo:X ≈ 1:2). These structurally robust crystals are ideal for optoelectronic, catalytic and pressure-tunable device applications.