Tailored growth of transition metal dichalcogenide monolayers and heterostructures for electronic and optoelectronic applications 2D transition metal dichalcogenides (TMDs) and their heterostructures have shown great potential for next generation device applications due to their unique and versatile electronic optical and chemical properties. However to exploit their potential in applications it is crucial to establish reliable and reproducible synthesis methods for these atomically thin materials. In addition efficient strategies for their synthesis with tailored properties must be developed. This work focuses on developing chemical vapor deposition (CVD) growth techniques for a range of TMD monolayers and their heterostructures understanding the underlying growth mechanism investigating their structure property relationships and exploring their functional applications. The work starts with the development of MoSe2 WSe2 lateral heterostructures demonstrating the formation of high quality atomically sharp p n junctions. The synthesis of Janus SeMoS TMDs with their unique asymmetric atomic configurations presents the emergence of novel optical phenomena such as valley Zeeman splitting. The work also innovates in the direct growth of TMD monolayers on curved photonic structures expanding the potential for photonic applications. In addition a novel area selective growth technique using micromolding in capillaries (MIMIC) is introduced leading to high quality TMD patterns for advanced electronic and optoelectronic devices.