Functionalization of group-14 two-dimensional materials

Abstract

The great success of graphene has boosted intensive search for other single-layer thick materials, mainly composed of group-14 atoms arranged in a honeycomb lattice. This new class of two-dimensional (2D) crystals, known as 2D-Xenes, has become an emerging field of intensive research due to their remarkable electronic properties and the promise for a future generation of nanoelectronics. In contrast to graphene, Xenes are not completely planar, and feature a low buckled geometry with two sublattices displaced vertically as a result of the interplay between sp and sp orbital hybridization. In spite of the buckling, the outstanding electronic properties of graphene governed by Dirac physics are preserved in Xenes too. The buckled structure also has several advantages over graphene. Together with the spin-orbit (SO) interaction it may lead to the emergence of various experimentally accessible topological phases, like the quantum spin Hall effect. This in turn would lead to designing and building new electronic and spintronic devices, like topological field effect transistors. In this regard an important issue concerns the electron energy gap, which for Xenes naturally exists owing to the buckling and SO interaction. The electronic properties, including the magnitude of the energy gap, can further be tuned and controlled by external means. Xenes can easily be functionalized by substrate, chemical adsorption, defects, charge doping, external electric field, periodic potential, in-plane uniaxial and biaxial stress, and out-of-plane long-range structural deformation, to name a few. This topical review explores structural, electronic and magnetic properties of Xenes and addresses the question of their functionalization in various ways, including external factors acting simultaneously. It also points to future directions to be explored in functionalization of Xenes. The results of experimental and theoretical studies obtained so far have many promising features making the 2D-Xene materials important players in the field of future nanoelectronics and spintronics.

Two-Dimensional Binary Honeycomb Layer Formed by Ag and Te on Ag(111)

“…Prominent examples are the discovery of graphene 1 and subsequent investigations of single-element graphene-analogues from group IV, such as silicene, germanene, and stanene. 2 Another type of 2D materials consists of high-Z (Z = atomic number) substitutional surface alloys on noble metals. Surface alloying is recognized as a viable way to achieve unique physical and chemical properties not found in the bulk.…”

“…The search for 2D materials for applications in the next generation of electronic and optoelectronic devices is currently quite intense. Prominent examples are the discovery of graphene and subsequent investigations of single-element graphene-analogues from group IV, such as silicene, germanene, and stanene . Another type of 2D materials consists of high- Z ( Z = atomic number) substitutional surface alloys on noble metals.…”

Magnetism in Au-Supported Planar Silicene

“…The great success of graphene [1,2] has triggered research into exploring alternative two-dimensional (2D) Dirac materials [3][4][5][6]. Among them, the group-14 2D graphene followers: silicene (Si), germanene (Ge), stanene (Sn), and plumbene (Pb), also known as 2D-Xenes [6][7][8][9], have attracted extensive interests. The crystal lattice of each freestanding Xene is predicted to be buckled on the atomic scale, and can be viewed as a structure with two sublattices displaced vertically as a result of the pseudo-Jahn-Teller (PJT) distortion [10].…”

Large bandgap quantum spin Hall insulator in methyl decorated plumbene monolayer: a first-principles study

“…Chemical decoration, 20,[22][23][24][25] application of electric eld, 26,27 substrate engineering 28 and absorption or adsorption adatoms 29,30 are among the few techniques that have been used for band gap opening as well as modication of topological properties in group IV monolayers. For the electric eld method, the bandgap opening is sometimes too small to operate at room temperature and breakdown electric eld of materials constraints the range of applied electric eld.…”