2D

**2D Materials in Semiconductors: MoS2, WSe2, and Graphene** is **atomically-thin layered materials exhibiting unique electronic properties enabling transistors, optoelectronic devices, and novel applications — offering tunable bandgaps, strong light-matter interaction, and potential for post-silicon scaling**. Transition metal dichalcogenides (TMDs) like Molybdenum Disulfide (MoS2) and Tungsten Diselenide (WSe2) are two-dimensional materials with layer-dependent bandgaps. Single-layer MoS2 has direct bandgap of 1.8eV; bilayers transition to indirect bandgap. This layer-dependent engineering enables bandgap tuning. MoS2 exhibits high carrier mobility in single layers despite being monolayer — ballistic transport with minimal scattering enables high ON/OFF current ratios. TMD transistors demonstrate subthreshold swing approaching theoretical limits. Strong light-matter interaction in TMDs enables efficient photoluminescence and photodetection. The oscillator strength is large, and direct bandgap enables absorption throughout the visible and near-infrared spectrum. Heterojunctions between different TMDs (MoS2/WSe2) show interesting optoelectronic properties. Graphene, a single sheet of carbon atoms in hexagonal lattice, is a semimetal with zero bandgap. High carrier mobility (100,000+ cm²/Vs) exceeds all other materials, enabling ballistic transport. However, lack of bandgap prevents switching for logic applications. Graphene excels in RF and analog applications where high mobility matters. Bilayer graphene can be band-opened through gate-induced strain, potentially enabling logic devices. Integration of graphene with other 2D materials offers opportunities. Heterostructure devices combining different 2D materials enable complex functionality. Black phosphorus, another 2D material, has strong anisotropy with direct bandgap enabling optoelectronic devices. V-group TMDs (VX2, where V=Ti,V,Cr; X=S,Se,Te) are investigated for exotic properties. Manufacturing 2D materials involves mechanical exfoliation for research, chemical vapor deposition (CVD) for wafer-scale growth, or liquid-phase exfoliation. CVD quality and uniformity remain challenges — defects and grain boundaries affect performance. Transfer to other substrates introduces contamination and strain. Integration with existing silicon processes requires careful substrate and interface engineering. Scaling to billions of transistors faces challenges of controlled synthesis and uniform quality. Reliability and lifetime of 2D devices remain understudied. Thermal properties, current density limitations, and degradation mechanisms require further research. **2D semiconductors offer unique physics and potential for novel devices, though commercialization requires breakthroughs in scalable manufacturing and integration with established semiconductor infrastructure.**