Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userCombined AFM and STM measurements of a silicene sheet grown on Ag(111) surface
214
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
In this Letter, we present the first non-contact atomic force microscopy (nc-AFM) of a silicene on silver (Ag) surface, obtained by combining non-contact atomic force microscopy (nc-AFM) and scanning tunneling microscopy (STM). STM images over large areas of silicene grown on Ag(111) surface show both (sqrt13xsqrt13)R13.9{deg} and (4x4) superstructures. For the widely observed (4x4) structure, the nc-AFM topography shows an atomic-scale contrast inversion as the tip-surface distance is decreased. At the shortest tip-surface distance, the nc-AFM topography is very similar to the STM one. The observed structure in the nc-AFM topography is compatible with only one out of two silicon atoms being visible. This indicates unambiguously a strong buckling of the silicene honeycomb layer.
rate research
Read More
The electronic and crystallographic structure of the graphene/Rh(111) moire lattice is studied via combination of density-functional theory calculations and scanning tunneling and atomic force microscopy (STM and AFM). Whereas the principal contrast between hills and valleys observed in STM does not depend on the sign of applied bias voltage, the contrast in atomically resolved AFM images strongly depends on the frequency shift of the oscillating AFM tip. The obtained results demonstrate the perspectives of application atomic force microscopy/spectroscopy for the probing of the chemical contrast at the surface.
A nanorod structure has been observed on the Ho/Ge(111) surface using scanning tunneling microscopy (STM). The rods do not require patterning of the surface or defects such as step edges in order to grow as is the case for nanorods on Si(111). At low holmium coverage the nanorods exist as isolated nanostructures while at high coverage they form a periodic 5x1 structure. We propose a structural model for the 5x1 unit cell and show using an ab initio calculation that the STM profile of our model structure compares favorably to that obtained experimentally for both filled and empty states sampling. The calculated local density of states shows that the nanorod is metallic in character.
The two-dimensional silicon allotrope, silicene, could spur the development of new and original concepts in Si-based nanotechnology. Up to now silicene can only be epitaxially synthesized on a supporting substrate such as Ag(111). Even though the structural and electronic properties of these epitaxial silicene layers have been intensively studied, very little is known about its vibrational characteristics. Here, we present a detailed study of epitaxial silicene on Ag(111) using textit{in situ} Raman spectroscopy, which is one of the most extensively employed experimental techniques to characterize 2D materials, such as graphene, transition metal dichalcogenides, and black phosphorous. The vibrational fingerprint of epitaxial silicene, in contrast to all previous interpretations, is characterized by three distinct phonon modes with A and E symmetries. The temperature dependent spectral evolution of these modes demonstrates unique thermal properties of epitaxial silicene and a significant electron-phonon coupling. These results unambiguously support the purely two-dimensional character of epitaxial silicene up to about $300^{circ}C$, whereupon a 2D-to-3D phase transition takes place.
Silicene, analogous to graphene, is a one-atom-thick two-dimensional crystal of silicon which is expected to share many of the remarkable properties of graphene. The buckled honeycomb structure of silicene, along with its enhanced spin-orbit coupling, endows silicene with considerable advantages over graphene in that the spin-split states in silicene are tunable with external fields. Although the low-energy Dirac cone states lie at the heart of all novel quantum phenomena in a pristine sheet of silicene, the question of whether or not these key states can survive when silicene is grown or supported on a substrate remains hotly debated. Here we report our direct observation of Dirac cones in monolayer silicene grown on a Ag(111) substrate. By performing angle-resolved photoemission measurements on silicene(3x3)/Ag(111), we reveal the presence of six pairs of Dirac cones on the edges of the first Brillouin zone of Ag(111), other than expected six Dirac cones at the K points of the primary silicene(1x1) Brillouin zone. Our result shows clearly that the unusual Dirac cone structure originates not from the pristine silicene alone but from the combined effect of silicene(3x3) and the Ag(111) substrate. This study identifies the first case of a new type of Dirac Fermion generated through the interaction of two different constituents. Our observation of Dirac cones in silicene/Ag(111) opens a new materials platform for investigating unusual quantum phenomena and novel applications based on two-dimensional silicon systems.
We report first-principles calculations that clarify stability and electronic structures of silicene on Ag(111) surfaces. We find that several stable structures exist for silicene/Ag(111), exhibiting a variety of images of scanning tunneling microscopy. We also find that Dirac electrons are {em absent} near Fermi energy in all the stable structures due to buckling of the Si monolayer and mixing between Si and Ag orbitals. We instead propose that either BN substrate or hydrogen processing of Si surface is a good candidate to preserve Dirac electrons in silicene.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
