Atomic Structures of Silicene Layers Grown on Ag(111): Scanning Tunneling Microscopy and Noncontact Atomic Force Microscopy Observations

Abstract

Silicene, the considered equivalent of graphene for silicon, has been recently synthesized on Ag(111) surfaces. Following the tremendous success of graphene, silicene might further widen the horizon of two-dimensional materials with new allotropes artificially created. Due to stronger spin-orbit coupling, lower group symmetry and different chemistry compared to graphene, silicene presents many new interesting features. Here, we focus on very important aspects of silicene layers on Ag(111): First, we present scanning tunneling microscopy (STM) and non-contact Atomic Force Microscopy (nc-AFM) observations of the major structures of single layer and bi-layer silicene in epitaxy with Ag(111). For the (3 × 3) reconstructed first silicene layer nc-AFM represents the same lateral arrangement of silicene atoms as STM and therefore provides a timely experimental confirmation of the current picture of the atomic silicene structure. Furthermore, both nc-AFM and STM give a unifying interpretation of the second layer (√3 × √3)R ± 30° structure. Finally, we give support to the conjectured possible existence of less stable, ~2% stressed, (√7 × √7)R ± 19.1° rotated silicene domains in the first layer.

The Critical Role of Substrate in Stabilizing Phosphorene Nanoflake: A Theoretical Exploration

“…The binding energy between the black P 27 nanoflake and the modified h-BN surface is about 0.35 eV/atom, close to that of silicene on the Ag(111) surface. 6,8 This implies that a substrate with moderate interaction strength is preferred for the epitaxial growth of phosphorene. The next step is to modify the interaction strength so as to satisfy the interaction criterion.…”

“…Stimulated by many miraculous properties of graphene, other two-dimensional (2D) materials, such as h-BN 1, 2 , transition metal dichalcogenides (TMDs) 3,4 , silicene [5][6][7][8] and phosphorene 9,10 , have also been produced and studied. Among those 2D materials, phosphorene, which was mechanically exfoliated in 2014, [9][10][11] is the latest member joining the 2D materials family.…”

Point defects in epitaxial silicene on Ag(111) surfaces

“…To date, silicene with various superstructures, including (4×4), ( 13 × 13 )R13.9º, ( 7 × 7 )R19.1º, (2 3 ×2 3 )R30º with respect to Ag(111) [31][32][33][34][35][36], and ( 3 × 3 ) with respect to silicene 1×1 lattice [11,31,37], have been fabricated on Ag(111) surfaces. Very recently, a silicene field-effect transistor (FET) was successfully fabricated following a growth-transfer-fabrication process, in which the silicene device was encapsulated by delamination with native electrodes [38].…”

Exceptional Optoelectronic Properties of Hydrogenated Bilayer Silicene

“…The freestanding bilayer silicene (BS), which is more stable than single-layer silicene, has been predicted to be an ideal material for topological insulators or superconductors [35,36] and Li-ion storage [37]. Although bilayer silicene has been synthesized in several experiments [24,26,[28][29][30][31][32], the ground-state structure of bilayer silicene, even in its freestanding form, is still under debate [35,[37][38][39].…”

“…The experimental progress demonstrates that single-and few-layer silicene can be synthesized by epitaxial growth on several substrates, e.g., Ag [23][24][25][26][27][28][29][30][31][32], Ir [33], and ZrB 2 [34]. The freestanding bilayer silicene (BS), which is more stable than single-layer silicene, has been predicted to be an ideal material for topological insulators or superconductors [35,36] and Li-ion storage [37].…”