In this study, we investigate the electronic structure of epitaxial planar silicene heterostructure grown on ultrathin gold films on the Si(111) substrates, covered by 0.1 monolayer of silver, ...antimony and lead. Angle-Resolved Photoemission Spectroscopy measurements reveal that the electronic structure of planar silicene, that shows bands with linear dispersion, remains largely unaffected by the presence of these dopants, with only a slight energy shift observed in the case of antimony. Density functional theory calculations corroborate these experimental observations, confirming the robustness of the epitaxial planar silicene heterostructure against surface doping. The results suggest that the intrinsic electronic properties of planar silicene are well-protected against surface contamination.
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Silicene, a single layer of Si atoms, shares many remarkable electronic properties with graphene. So far, silicene has been synthesized in its epitaxial form on a few surfaces of solids. Thus, the ...problem of silicene–substrate interaction appears, which usually depresses the original electronic behavior but may trigger properties superior to those of bare components. We report the direct observation of robust Dirac-dispersed bands in epitaxial silicene grown on Au(111) films deposited on Si(111). By performing in-depth angle-resolved photoemission spectroscopy measurements, we reveal three pairs of one-dimensional bands with linear dispersion running in three different directions of an otherwise two-dimensional system. By combining these results with first-principles calculations, we explore the nature of these bands and point to strong interaction between subsystems forming a complex Si–Au heterostructure. These findings emphasize the essential role of interfacial coupling and open a unique materials platform for exploring exotic quantum phenomena and applications in future-generation nanoelectronics.
Regular arrays of silicon terraces with coexisting two gold-induced one-dimensional structures have been synthesized on the Si(11 11 13) surface. For the first time, it was possible to confine the ...well-known 5 × 2-Au reconstruction to narrow stripes separated by atomic steps and preserving its basic properties. Moreover, each terrace consists of additional chain of gold atoms that shows the same crystallographic and electronic properties to the Si(557)-Au surface. The results obtained by scanning tunneling microscopy and angle-resolved photoemission spectroscopy supplemented by first-principles density functional theory calculations allow to identify fingerprints of 5 × 2-Au and Si(557)-Au structures occupying the same terrace. This contrasts with the whole family of gold chains on vicinal silicon surfaces and presents new paradigm in engineering of complex one-dimensional nanostructures on stepped surfaces.
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•Coexistence of different 1D structures on a single surface terrace.•Multiple one-dimensional metallic electron bands.•New paradigm for the synthesis of complex one-dimensional materials on stepped surfaces.
Metallic atomic chains weakly coupled to the substrate may be a practical implementation of extreme one-dimensional quantum systems. We report a two-step method of assembling one-dimensional Sb ...atomic chains on an ordered stepped Si(553) surface with Pb nanoribbons. We show that Pb atoms act as a surfactant, induce the dissociation of Sb molecules, and enable the formation of monatomic chains. Combining atomistic modeling within density functional theory with scanning tunneling microscopy and angle-resolved photoemission spectroscopy, we demonstrate that the formed Sb chains are highly strained and at the same time electronically isolated, exhibiting extremely well-defined one-dimensional free-electron like behavior.
We report on a giant Rashba type splitting of metallic bands observed in one-dimensional structures prepared on a vicinal silicon substrate. A single layer of Pb on Si(553) orders this vicinal ...surface making perfectly regular distribution of monatomic steps. Although there is only one layer of Pb, the system reveals very strong metallic and purely one-dimensional character, which manifests itself in multiple surface state bands crossing the Fermi level in the direction parallel to the step edges and a small band gap in the perpendicular direction. As shown by spin-polarized photoemission and density functional theory calculations these surface state bands are spin-polarized and completely decoupled from the rest of the system. The experimentally observed spin splitting of 0.6 eV at room temperature is the largest found to now in the silicon-based metallic nanostructures, which makes the considered system a promising candidate for application in spintronic devices.
2D sheets of graphene‐like silicon, namely planar silicene, are synthesized. This new silicon allotrope is prepared on Au(111) thin films grown on a Si(111) substrate in the process of surface ...segregation. Owing to its almost perfectly flat geometry it shares the atomic structure with graphene rather than with low‐buckled silicene. Scanning tunneling microscopy measurements clearly display an atomically resolved planar silicene honeycomb lattice. Ab initio density functional theory calculations fully support the experimental findings and predict a pure sp2 atomic configuration of Si atoms. The present work is the first experimental evidence of epitaxial planar silicene.
Planar silicene, a novel silicon allotrope, is synthesized on a Au(111) substrate in the process of surface segregation. The lattice constant of planar silicene is almost 6% longer and the buckling lower by an order of magnitude with respect to the freestanding silicene values. Density functional theory calculations predict a perfectly flat honeycomb Si lattice with a pure sp2 atomic configuration.
Tuning the ambipolar behavior in charge carrier transport via defect-engineering is crucial for achieving high mobility transistors for nonlinear logic circuits. Here, we present the electric-field ...tunable electron and hole transport in a microchannel device consisting of highly air-stable van der Waals (vdW) noble metal dichalcogenide (NMDC), PdSe2, as an active layer. Pristine bulk PdSe2 constitutes Se surface vacancy defects created during the growth or exfoliation process and offers ambipolar transfer characteristics with a slight electron dominance recorded in field-effect transistor (FET) characteristics showing an ON/OFF ratio <10 and electron mobility ∼21 cm2/(V·s). However, transfer characteristics of PdSe2 can be tuned to a hole-dominated transport while using hydrochloric acid (HCl) as a p-type dopant. On the other hand, the chelating agent EDTA, being a strong electron donor, enhances the electron-dominance in PdSe2 channel. In addition, p-type behavior with a 100 times higher ON/OFF ratio is obtained while cooling the sample down to 10 K. Low-temperature angle-resolved photoemission spectroscopy resembles the p-type band structure of PdSe2 single crystal. Also, first principle density functional theory calculations justify the tunability observed in PdSe2 as a result of defect-engineering. Such a defect-sensitive ambipolar vdW architecture may open up new possibilities toward future CMOS (Complementary Metal-Oxide-Semiconductor) device fabrications and high performance integrated circuits.
The discovery of graphene with its massless fermions established a new branch of nanomaterials in which linear bands can be realized. It has been predicted that beside Dirac fermions revealing ...isotropic character and observed in a number of two-dimensional materials, another class of massless fermions can also be found: strongly anisotropic fortune teller-like states which form planes instead of cones in the electronic structure. Here, we demonstrate that such distinct electronic structures exist and can be found in a surface layer of silicon.
Massless fermions forming fortune teller states in a surface layer of Si(110).
The interaction between graphene and germanium surfaces was investigated using a combination of microscopic and macroscopic experimental techniques and complementary theoretical calculations. Density ...functional theory (DFT) calculations for different reconstructions of the Ge(001) surface showed that the interactions between graphene and the Ge(001) surface introduce additional peaks in the density of states, superimposed on the graphene valence and conduction energy bands. The growth of graphene induces nanofaceting of the Ge(001) surface, which exhibits well-organized hill and valley structures. The graphene regions covered by hills are of high quality and exhibit an almost linear dispersion relation, which indicates weak graphene–germanium interactions. On the other hand, the graphene component occupying valley regions is significantly perturbed by the interaction with germanium. It was also found that the stronger graphene–germanium interaction observed in the valley regions is connected with a lower local electrical conductivity. Annealing of graphene/Ge(001)/Si(001) was performed to obtain a more uniform surface. This process results in a surface characterized by negligible hill and valley structures; however, the graphene properties unexpectedly deteriorated with increasing uniformity of the Ge(001) surface. To sum up, it was shown that the mechanism responsible for the formation of local conductivity inhomogeneities in graphene covering the Ge(001) surface is related to the different strength of graphene–germanium interactions. The present results indicate that, in order to obtain high-quality graphene, the experimental efforts should focus on limiting the interactions between germanium and graphene, which can be achieved by adjusting the growth conditions.
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