A Novel Two-Dimensional Allotrope of Silicon Grown on Al(111): A Case Study of the Interface Effect

Abstract

Based on density functional calculations, a novel planar allotrope of silicon on Al( 111) is rationally designed by using the lowest energy principle, which is also predicted to be stable above room temperature to suggest the possibility for its fabrication. The corresponding free-standing sheet would be buckled though the structural characteristics still remain, whose stability has also been evaluated in detail. It has been found to have strong anisotropic properties to be as hard as silicene in a specific direction and to be very soft in the perpendicular direction. Surprisingly, a peculiar negative Poisson's ratio showing unusual mechanical properties is also found. The indirect bandgap of 0.14 eV of the free-standing sheet could be closed by applying tensile strain. Interestingly, the Dirac cone of the orthogonal lattice allotrope sheet can be obtained by applying biaxial strain, for which the velocity of the charge carriers could reach 5.97 × 10 5 m/s. In addition, the hydrogenated sheet is also quite stable and may find usage for sunlight absorption, field-effect transistor, etc., which may be decorated with Ti, Fe, or Co adsorptions to have half-metallic conducting properties for spin filtering.

Novel Graphene Allotropes Designed by Polymerizing Pyracyclene Molecules

“…The t - and h -PBAs are calculated to have −1.00 and −1.17 eV/atom formation energies, indicating the possibilities of their fabrications. In addition, considering the fact that (111)-oriented metallic surfaces of Au, ,,, Pt, , Al ,, metals, etc. are usually used as substrates for 2D material fabrications in experiments, we have performed a tentative study by putting PBAs on the Al(111) surface.…”

“…As shown in Figure 1a, the pyracyclene molecule has a planar structure consisting of two C 6 hexagons and two C 5 pentagons, 32,33 having similar geometrical configuration characteristics as to the structural motif of a recently proposed silicene allotrope grown on an Al(111) surface. 31 In Figure 1a, the nonequivalent C atoms are marked to facilitate discussion. The 1,2-, 2,3-, and 2,4-bonds are calculated to be 1.49, 1.39, and 1.41 Å, respectively.…”

“…However, by using bottom-up surface-assisted synthesis procedures with dehydrogenated molecules as precursors, − the net-graphene nanoribbon and bipheneylene sheet, both containing 4-, 6-, and 8-membered carbon rings, were successfully synthesized through experiment by Liu et al and Fan et al, respectively, which added relevance for fabricating various theoretically proposed graphene allotropes with corresponding dehydrogenated organic molecules as precursors. Inspired by these experimental achievements and the similar structural characteristics of a bulked silicene allotrope grown on Al(111) with the organic molecule pyracyclene, , we have carried out detailed studies of the novel graphene allotropes designed by polymerizing pyracyclene molecules. Their high stabilities support the possibility of their experimental fabrication through the on-surface interpolymer dehydrofluorination reaction method .…”

From Topological Nodal-Line Semimetal to Insulator in ABW-Ge4: A New Member of the Germanium Allotrope

“…Owing to the complex potential energy surface, the Group-IV elements can form various allotropes with different structural and electronic properties, which provides promising platforms for constructing multifunctional microelectronic devices. Hence, the searching for stable Group-IV allotropes has attracted considerable attention from both theoretical and experimental researchers. − However, these studies mainly focus on carbon (C) and silicon (Si), and the studies about germanium (Ge) allotropes are relatively few. The most prominent Ge allotrope is the diamond-cubic Ge, denoted as dc-Ge, which has higher electron and hole mobilities, and smaller indirect band gap with respect to that of dc-Si .…”

Excellent thermoelectric transport performance in semiconducting hhk-silicene

“…In very recent years, new two-dimensional silicon allotropes were discovered theoretically. For example, Ding et al [25] designed a novel planar allotrope of silicon on Al(111) and found that the hydrogenated sheet is also quite stable than freestanding one. More interestingly, Sang et al [26] discovered a two-dimensional allotrope with hybrid honeycomb-kagome (hhk) lattice, which is a semiconductor instead of quasi-zero Dirac-cone like graphene and graphene-like silicene.…”