Modern 2D Heterostructures: From Fabrication Challenges to Emerging Applications

The pursuit of next-generation electronics and optoelectronics increasingly demands material platforms that overcome the inherent constraints of individual semiconductors. Heterostructures, particularly those constructed from low-dimensional and two-dimensional (2D) materials, provide unprecedented opportunities to tune band alignment, interlayer coupling, and charge dynamics, thereby enabling functionalities unattainable in single-component systems. Despite these advantages, the practical fabrication of high-quality heterostructures remains a formidable challenge. Issues such as interfacial contamination during mechanical transfer, defect generation in chemical vapor deposition (CVD), and lattice mismatch in molecular beam epitaxy (MBE) often lead to poor reproducibility, limited scalability, and compromised device performance. This review provides a comprehensive analysis of difficulties in fabricating modern heterostructures, with emphasis on mechanical assembly methods, direct growth approaches, and wafer-scale integration. We further categorize heterostructures into vertical, lateral, and mixed-dimensional systems, while examining their excitonic phenomena in transition metal dichalcogenide (TMD) platforms, including intralayer/interlayer excitons as well as moiré superlattices. The broad scope of applications is also discussed, covering electronic devices, neuromorphic and synaptic systems, optoelectronic technologies, as well as versatile sensing and catalytic platforms. By systematically addressing fabrication challenges and their implications, this review highlights critical opportunities and outlines future perspectives to accelerate the integration of heterostructures into practical technologies.