39 research outputs found
Phosphorene: Fabrication, Properties and Applications
Phosphorene, the single- or few-layer form of black phosphorus, was recently
rediscovered as a twodimensional layered material holding great promise for
applications in electronics and optoelectronics. Research into its fundamental
properties and device applications has since seen exponential growth. In this
Perspective, we review recent progress in phosphorene research, touching upon
topics on fabrication, properties, and applications; we also discuss challenges
and future research directions. We highlight the intrinsically anisotropic
electronic, transport, optoelectronic, thermoelectric, and mechanical
properties of phosphorene resulting from its puckered structure in contrast to
those of graphene and transition-metal dichalcogenides. The facile fabrication
and novel properties of phosphorene have inspired design and demonstration of
new nanodevices; however, further progress hinges on resolutions to technical
obstructions like surface degradation effects and non-scalable fabrication
techniques. We also briefly describe the latest developments of more
sophisticated design concepts and implementation schemes that address some of
the challenges in phosphorene research. It is expected that this fascinating
material will continue to offer tremendous opportunities for research and
development for the foreseeable future.Comment: invited perspective for JPC
Silicene structures on silver surfaces
In this paper we report on several structures of silicene, the analog of
graphene for silicon, on the silver surfaces Ag(100), Ag(110) and Ag(111).
Deposition of Si produces honeycomb structures on these surfaces. In
particular, we present an extensive theoretical study of silicene on Ag(111)
for which several recent experimental studies have been published. Different
silicene structures were obtained only by varying the silicon coverage and/or
its atomic arrangement. All the structures studied show that silicene is
buckled, with a Si-Si nearest neighbor distance varying between 2.28 and 2.5
A{\deg} . Due to the buckling in the silicene sheet, the apparent (lateral)
Si-Si distance can be as low as 1.89 A{\deg} . We also found that for a given
coverage and symmetry, one may observe different scanning tunneling microscopy
images corresponding to structures that differ by only a translation.Comment: To be published in in J. Phys.: Condens. Matter "Special Issue on
Ultrathin layers of graphene, h-BN and other honeycomb structures
Tuning the band gap in silicene by oxidation
Silicene monolayers grown on Ag(111) surfaces demonstrate a band gap that is tunable by oxygen adatoms from semimetallic to semiconducting type. With the use of low-temperature scanning tunneling microscopy, we find that the adsorption configurations and amounts of oxygen adatoms on the silicene surface are critical for band gap engineering, which is dominated by different buckled structures in √13 x √13, 4 x 4, and 2√3 x 2√3 silicene layers. The Si-O-Si bonds are the most energy-favored species formed on √13 x √13, 4 x 4, and 2√3 x 2√3 structures under oxidation, which is verified by in situ Raman spectroscopy as well as first-principles calculations. The silicene monolayers retain their structures when fully covered by oxygen adatoms. Our work demonstrates the feasibility of tuning the band gap of silicene with oxygen adatoms, which, in turn, expands the base of available two-dimensional electronic materials for devices with properties that is hardly achieved with graphene oxide
Soliton-dependent plasmon reflection at bilayer graphene domain walls
Layer-stacking domain walls in bilayer graphene are emerging as a fascinating one-dimensional system that features stacking solitons structurally and quantum valley Hall boundary states electronically. The interactions between electrons in the 2D graphene domains and the one-dimensional domain-wall solitons can lead to further new quantum phenomena. Domain-wall solitons of varied local structures exist along different crystallographic orientations, which can exhibit distinct electrical, mechanical and optical properties. Here we report soliton-dependent 2D graphene plasmon reflection at different 1D domain-wall solitons in bilayer graphene using near-field infrared nanoscopy. We observe various domain-wall structures in mechanically exfoliated graphene bilayers, including network-forming triangular lattices, individual straight or bent lines, and even closed circles. The near-field infrared contrast of domain-wall solitons arises from plasmon reflection at domain walls, and exhibits markedly different behaviours at the tensile- and shear-type domain-wall solitons. In addition, the plasmon reflection at domain walls exhibits a peculiar dependence on electrostatic gating. Our study demonstrates the unusual and tunable coupling between 2D graphene plasmons and domain-wall solitons