External-strain-induced semimetallic and metallic phase of chlorographene

Abstract

In order to overcome the limitations of graphene due to lack of intrinsic bandgap, it is generally functionalized with hydrogen or halogen atoms like fluorine and chlorine. Generally, such functionalization yields a moderate to high bandgap material in case of 100% coverage, for example ≈ 1.5 eV in graphene functionalized with chlorine atoms or chlorographene. In this paper, using ab initio calculations, we report very interesting transformations observed in chlorographene under external strain, driving it to a state with nearly vanishing bandgap (under tensile strain) and even converting it to a metal (under compressive strain). We also show the importance of spin-orbit coupling, responsible for the few meV bandgap of chlorographene observed under high tensile strain, which would have been a gapless semi-metal otherwise.The past decade has seen a tremendous growth of two dimensional (2D) materials, with numerous discoveries of atomically thin layers with fascinating properties suitable for applications in next generation electronic, optoelectronic and magnetic devices. 1 The rise of 2D materials started with the first successful isolation of a single layer of graphite, known as graphene. 2-4 Post-discovery, graphene enthralled the researches with it's fascinating electronic-transport properties like quantum Hall Effect at room temperature, very high carrier mobility, long mean free path and ballistic transport of electrons. 4 In addition to this, superior mechanical strength, high thermal conductivity and remarkable flexibility of graphene makes it an ideal candidate for device applications.The origin of exotic electronic-transport properties of graphene lies in it's linear energy dispersion (resembling the Dirac spectrum of massless fermions) at the highsymmetry points located at the six corners (denoted as K points) of the hexagonal Brillouin zone. 5,6 Since the highest occupied and lowest unoccupied band touches each other at the Dirac points (K points), graphene is classified as a semi-metal. Unfortunately, lack of intrinsic bandgap limits the use of graphene to some extent. For example, the advantage of ultrahigh electron mobility is nullified by high off current in graphene based field effect transistor (FET) devices.Fabrication of nanoribbons and quantum dots is one possible solution, as bandgap appears due to quantum confinement effect. 7 Although graphene nanoribbons have several interesting features, like spontaneous spin polarization along the edges, their fabrication with atomically controlled edge shapes remains a challange. [8][9][10] Other alternative is to functionalize graphene via chemical adsorption of hydrogen 11,12 or halogen atoms like fluorine 13-16 and chlorine. [17][18][19] Unfortunately, this leads to a large bandgap of magnitude 3.5-3.7 eV in case of hydrogenation, 2.9-3.1 eV in case of fluorination and 1.2-1.5 eV in case of chlorination, as reported in several computational and experimental studies. [11][12][13][14][15][16][17][18][19] Reducing the bandgap is certainly going to make t...

Versatility of the SiH–CdCl2 Heterostructure: Piezoelectricity, Photocatalysis, and Transistor Applications

“…Since the experimental discovery of graphene, numerous two-dimensional (2D) materials have been extensively explored due to their exceptional electrical, mechanical, optical, and catalytic properties. These include transition-metal dichalcogenides (TMDs), group-V materials like phosphorene, and group-IV materials like silicene among others. − To impart additional functionality to 2D materials beyond their intrinsic properties, various techniques such as chemical functionalization, surface adsorption, strain engineering, and quantum confinement are used. − Owing to their tunable properties, van der Waals (vdW) heterostructures have emerged as a promising class of 2D materials. , These heterostructures are formed by stacking monolayers in desired sequences, allowing for the tailoring of material properties for specific applications. − …”