Growth and investigation of two dimensional metal halide and transition metal dichalcogenide materials for optoelectronic applications

Novel materials and device architecture-based technologies are needed to extend optoelectronic device performance beyond the scaling limits of Moore's law. Two-dimensional (2D) semiconductor materials can have important structural and electronic properties, such as high surface-to-volume ratio, wide optical absorption band gap, and high charge mobility value, due to their atomically fine structures and quantum confinement effects. Within the scope of the thesis, metal halide 2D bismuth triiodide (BiI3) and transition metal dichalcogenide monolayer 2D molybdenum disulfide (MoS2) materials, which have the potential to give important results in terms of optoelectronic applications, have been produced with high crystallinity and large area. During the synthesis of the materials, physical vapor transport, gold layer assisted exfoliation and chemical vapor deposition methods were used. Detailed structural and optical examination of materials has been carried out by using optical imaging, scanning electron microscopy/energy dispersive X-ray spectroscopy, X-ray diffractometry, atomic force microscopy, 3D laser scanning confocal microscopy, optical absorption spectroscopy, Raman spectroscopy, and photoluminescence (PL) spectroscopy. In addition to revealing the high crystallinity properties of both materials, it has been shown by PL and Raman analyzes that the indirect energy transitions from the band structure to the direct band structure. BiI3 nanocrystals could be produced with a wide lateral area of tens of microns, a layered structure under 10 nanometers thick, and preserving their crystalline properties. Depending on the thickness, PL shifts of up to 576 nanometers were observed in BiI3 nanocrystals. In addition, the effects of growth pressure, temperature and duration on crystal growth were examined and it was found that 25 Torr, 290 oC and zero minutes waiting time were the optimum conditions for ultrathin crystal formation. On the other hand, MoS2 nanocrystals were synthesized with a single layer thickness (0.64 nm) and a large lateral area of tens of microns. In addition, centimeter-sized single-layer MoS2 films were also grown in this thesis. Monolayer production was confirmed by showing that the difference between Raman modes was 21.14 and 19.66 cm-1 for triangular prism crystals and film, respectively. As a result of the analysis, it was revealed that the PL peaks were 680 and 645 nm, respectively. Within the scope of the thesis, the production and detailed investigations of 2D metal halide and transition metal dialcogenide nanostructures in one or more layered forms have contributed to the knowledge pool on the structural and optical properties of these materials.