2D materials advances: from large scale synthesis and controlled heterostructures to improved characterization techniques, defects and applications

Abstract

The rise of two-dimensional (2D) materials research took place following the isolation of graphene in 2004. These new 2D materials include transition metal dichalcogenides, mono-elemental 2D sheets, and several carbide-and nitride-based materials. The number of publications related to these emerging materials has been drastically increasing over the last five years. Thus, through this comprehensive review, we aim to discuss the most recent groundbreaking discoveries as well as emerging opportunities and remaining challenges. This review starts out by delving into the improved methods of producing these new 2D materials via controlled exfoliation, metal organic chemical vapor deposition, and wet chemical means. We look into recent studies of doping as well as the optical properties of 2D materials and their heterostructures. Recent advances towards applications of these materials in 2D electronics are also reviewed, and include the tunnel MOSFET and ways to reduce the contact resistance for fabricating highquality devices. Finally, several unique and innovative applications recently explored are discussed as well as perspectives of this exciting and fast moving field.

Thin 2D: The New Dimensionality in Gas Sensing

“…Most importantly, the synthesis processes should allow for the control of the final properties exhibited by the thin 2D material, preserving the crystalline structure of each individual inorganic layer, with a controllable number of atomic layers and atomically sharp interfaces [37]. This aspect is necessary for ensuring the device reliability requested for practical applications.…”

Atlas for the properties of elemental two-dimensional metals

“…Graphene, for example, is extremely strong [5], has high thermal conductivity [6] and high charge carrier mobility [7], and can exhibit the quantum Hall effect [8,9]. Many other 2D materials, such as hexagonal boron nitride and transition-metal chalcogenides, are also investigated for their exceptional properties and promising applications [10][11][12][13][14]. The structure of these 2D materials is related to the nature of their bonding.…”

Optically Discriminating Carrier-Induced Quasiparticle Band Gap and Exciton Energy Renormalization in MonolayerMoS2

“…In ML-TMDCs, electronic excitations are collective phenomena that are described by a quasiparticle band structure which condenses the excitations into particles with momentum and energy that reflect the underlying many-body physics and crystal structure [8,9]. The energetic separation between the quasiparticle valence and conduction bands, termed the 'quasiparticle band gap' or simply the 'band gap', governs the electronic properties in ML-TMDCs such as transport, formation of Ohmic contacts and band alignment in heterostructures [10][11][12][13][14]. Meanwhile, photoexcitations, which are essential to optoelectronic functionality [15][16][17][18][19], create electron-hole pairs within the quasiparticle band structure, forming a rich manifold of bound exciton states.…”