60 research outputs found
Investigation of Electron-Phonon Coupling in Epitaxial Silicene by In-situ Raman Spectroscopy
In this letter, we report that the special coupling between Dirac fermion and
lattice vibrations, in other words, electron-phonon coupling (EPC), in silicene
layers on Ag(111) surface was probed by an in-situ Raman spectroscopy. We find
the EPC is significantly modulated due to tensile strain, which results from
the lattice mismatch between silicene and the substrate, and the charge doping
from the substrate. The special phonon modes corresponding to two-dimensional
electron gas scattering at edge sites in the silicene were identified.
Detecting relationship between EPC and Dirac fermion through the Raman
scattering will provide a direct route to investigate the exotic property in
buckled two-dimensional honeycomb materials.Comment: 15 pages, 4 figure
Quasi-freestanding epitaxial silicene on Ag(111) by oxygen intercalation
Silicene is a monolayer allotrope of silicon atoms arranged in a honeycomb structure with massless Dirac fermion characteristics similar to graphene. It merits development of silicon-based multifunctional nanoelectronic and spintronic devices operated at room temperature because of strong spin-orbit coupling. Nevertheless, until now, silicene could only be epitaxially grown on conductive substrates. The strong silicene-substrate interaction may depress its superior electronic properties. We report a quasi-freestanding silicene layer that has been successfully obtained through oxidization of bilayer silicene on the Ag(111) surface. The oxygen atoms intercalate into the underlayer of silicene, resulting in isolation of the top layer of silicene from the substrate. In consequence, the top layer of silicene exhibits the signature of a 1 x 1 honeycomb lattice and hosts massless Dirac fermions because of much less interaction with the substrate. Furthermore, the oxidized silicon buffer layer is expected to serve as an ideal dielectric layer for electric gating in electronic devices. These findings are relevant for the future design and application of silicene-based nanoelectronic and spintronic devices
Resistance Switching Behavior in Rectangle-Nano-Pattern SrTiO3 Induced by Simple Annealing.
The tunability of semi-conductivity in SrTiO3 single crystal substrates has been realized by a simple encapsulated annealing method under argon atmosphere. This high temperature annealing-induced property changes are characterized by the transmission spectra, scanning electron microscopy (SEM) and synchrotron-based X-ray absorption (XAS). We find the optical property is strongly influenced by the annealing time (with significant decrease of transmittance). A sub gap absorption at ~427 nm is detected which is attributed to the introduction of oxygen vacancy. Interestingly, in the SEM images, annealing-induced regularly rectangle nano-patterns are directly observed which is contributed to the conducting filaments. The XAS of O K-edge spectra shows the changes of electronic structure by annealing. Very importantly, resistance switching response is displayed in the annealed SrTiO3 single crystal. This suggests a possible simplified route to tune the conductivity of SrTiO3 and further develop novel resistance switching materials
Effects of Oxygen Adsorption on the Surface State of Epitaxial Silicene on Ag(111)
Epitaxial silicene, which is one single layer of silicon atoms packed in a
honeycomb structure, demonstrates a strong interaction with the substrate that
dramatically affects its electronic structure. The role of electronic coupling
in the chemical reactivity between the silicene and the substrate is still
unclear so far, which is of great importance for functionalization of silicene
layers. Here, we report the reconstructions and hybridized electronic
structures of epitaxial 4x4 silicene on Ag(111), which are revealed by scanning
tunneling microscopy and angle-resolved photoemission spectroscopy. The
hybridization between Si and Ag results in a metallic surface state, which can
gradually decay due to oxygen adsorption. X-ray photoemission spectroscopy
confirms the decoupling of Si-Ag bonds after oxygen treatment as well as the
relatively oxygen resistance of Ag(111) surface, in contrast to 4x4 silicene
[with respect to Ag(111)]. First-principles calculations have confirmed the
evolution of the electronic structure of silicene during oxidation. It has been
verified experimentally and theoretically that the high chemical activity of
4x4 silicene is attributable to the Si pz state, while the Ag(111) substrate
exhibits relatively inert chemical behavior.Comment: 18 pages, 4 figures, accepted by Scientific Report
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