Interaction of silicene withβ-Si₃N₄(0001)/Si(111) substrate; energetics and electronic properties

Abstract

The free-standing, quasi-2D layer of Si is known as silicene, in analogy with graphene. Much effort is devoted in the study of silicene, since, similarly to graphene, it shows a very high electron mobility. The interaction of silicene with a hybrid substrate, β-Si3N4(0001)/Si(111), exposing the β-Si3N4(0001) surface, has been studied by means of Density Functional calculations, with van der Waals interactions included. Once deepened the most important structural and electronic features of the hybrid substrate, we demonstrated that an electron transfer occurs from the substrate to the silicene layer. In turn, such an electron transfer can be modulated by the doping of the substrate. The β-Si3N4/silicene interaction appears to be strong enough to ensure adequate adsorption stability. It is also shown that electronic states of substrate and adsorbate still remain decoupled, paving the way for the exploitation of the peculiar electron mobility properties of the silicene layer. A detailed analysis in both direct and reciprocal space is reported.

Silicene: Recent theoretical advances

“…120 The Dirac cone is also disturbed by a substrate band on Hpassivated Si 3 N 4 (0001), but can be restored by n-type P substitution at the Si site with a band gap of 58 meV. 121 The Dirac cones are predicted on H/F-passivated Si (111) and Hpassivated SiC(0001) substrates with lattice mismatches less than 1%. [122][123][124][125] H-passivated Ge(111) behaves similarly, but has a larger lattice mismatch of 4%.…”

Nearly-free electronlike surface resonance of aβ−Si3N4(0001)/Si(111)−8×8<

“…Indeed, Flage-Larsen et al performed a bulk simulation with two β-Si 3 N 4 /Si interfaces, while we used just one interface, simulating a surface rather than a bulk. The other difference is the presence of flat states in the conduction band between K andM high symmetry points; such states originate from unsaturated orbitals belonging to surface atoms, as they are wiped off when the surface is saturated with H atoms [13].…”

“…This is of paramount importance as metal/Si(111) ideal interfaces can now be produced without the drawbacks of the formation of interface states due to silicides. Recently epitaxial β-Si 3 N 4 (0001) films grown on Si(111) have been also suggested to be ideal substrates to preserve the high mobility properties of graphene [12] and silicene [13].…”

Functionalization of group-14 two-dimensional materials

“…In general it is true that the weaker Xene-substrate interaction the less affected DC. Many theoretical calculations indicate that the Xene's band structure will be preserved when the Xene-substrate interaction is of the van der Waals type, like for hydrogen-and halogen-passivated semiconductor surfaces [122,279,[309][310][311][312][313][314], chalcogenides [259][315-326], group-14 hybrids [242,258,[327][328][329] and other surfaces [36,304,309,310,312,[330][331][332][333][334][335][336][337][338][339][340][341][342].…”