Nanofilm Allotrope and Phase Transformation of Ultrathin Bi Film on Si(111)-7×7
TL;DR: It is proposed that the new allotrope of Bi consists of black phosphorus-like puckered layers stabilized by saturating all the p(z) dangling bonds in the film.
Abstract: Our scanning tunneling microscopy and electron diffraction experiments revealed that a new two-dimensional allotrope of Bi forms on the Si(111)-7x7 surface. This pseudocubic [012]-oriented allotrope is stable up to four atomic layers at room temperature. Above this critical thickness, the entire volume of the film starts to transform into a bulk single-crystal (001) phase, as the bulk contribution in the cohesion becomes dominant. Based on ab initio calculations, we propose that the new allotrope consists of black phosphorus-like puckered layers stabilized by saturating all the p(z) dangling bonds in the film.
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TL;DR: In this review, the latest theoretical and experimental progress made in the fundamental properties, fabrications and applications of 2D group-VA materials are explored, and perspectives and challenges for the future of this emerging field are offered.
Abstract: Phosphorene, an emerging two-dimensional material, has received considerable attention due to its layer-controlled direct bandgap, high carrier mobility, negative Poisson's ratio and unique in-plane anisotropy. As cousins of phosphorene, 2D group-VA arsenene, antimonene and bismuthene have also garnered tremendous interest due to their intriguing structures and fascinating electronic properties. 2D group-VA family members are opening up brand-new opportunities for their multifunctional applications encompassing electronics, optoelectronics, topological spintronics, thermoelectrics, sensors, Li- or Na-batteries. In this review, we extensively explore the latest theoretical and experimental progress made in the fundamental properties, fabrications and applications of 2D group-VA materials, and offer perspectives and challenges for the future of this emerging field.
689 citations
25 Jan 2017
TL;DR: A review of recent progress and current challenges in the synthesis and stabilization of elemental 2D materials can be found in this article, with a focus on topical species with peculiar properties and properties.
Abstract: This Review covers recent progress and current challenges in the synthesis and stabilization of elemental 2D materials — topical species with peculiar properties. The further development of preparative methodologies will help to expand the 2D materials library well beyond naturally occurring layered materials, and afford products with unique structures and functions.
625 citations
TL;DR: In this paper, the effect of the spin-orbit interaction on low-index surfaces of the group V semimetal bismuth has been studied and the main focus is on the geometric and electronic structure.
461 citations
TL;DR: The calculations show that free-standing α and β allotropes of antimonene are stable and semiconducting, which opens up the possibility of their applications in optoelectronics.
Abstract: Group V elemental monolayers including phosphorene are emerging as promising 2D materials with semiconducting electronic properties. Here, we present the results of first-principles calculations on stability, mechanical and electronic properties of 2D antimony (Sb), antimonene. Our calculations show that free-standing α and β allotropes of antimonene are stable and semiconducting. The α-Sb has a puckered structure with two atomic sublayers and β-Sb has a buckled hexagonal lattice. The calculated Raman spectra and STM images have distinct features thus facilitating characterization of both allotropes. The β-Sb has nearly isotropic mechanical properties, whereas α-Sb shows strongly anisotropic characteristics. An indirect–direct band gap transition is expected with moderate tensile strains applied to the monolayers, which opens up the possibility of their applications in optoelectronics.
418 citations
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TL;DR: In this article, the authors proposed a truncated icosahedron, a polygon with 60 vertices and 32 faces, 12 of which are pentagonal and 20 hexagonal.
Abstract: During experiments aimed at understanding the mechanisms by which long-chain carbon molecules are formed in interstellar space and circumstellar shells1, graphite has been vaporized by laser irradiation, producing a remarkably stable cluster consisting of 60 carbon atoms. Concerning the question of what kind of 60-carbon atom structure might give rise to a superstable species, we suggest a truncated icosahedron, a polygon with 60 vertices and 32 faces, 12 of which are pentagonal and 20 hexagonal. This object is commonly encountered as the football shown in Fig. 1. The C60 molecule which results when a carbon atom is placed at each vertex of this structure has all valences satisfied by two single bonds and one double bond, has many resonance structures, and appears to be aromatic. Before 1985, it was generally accepted that elemental carbon exists in two forms, or allotropes: diamond and graphite. Then, Kroto et al. identified the signature of a new, stable form of carbon that consisted of clusters of 60 atoms. They called this third allotrope of carbon 'buckminsterfullerene', and proposed that it consisted of polyhedral molecules in which the atoms were arrayed at the vertices of a truncated icosahedron. In 1990, the synthesis of large quantities of C60 [see Nature 347, 354–358 (1990)] confirmed this hypothesis.
13,394 citations
TL;DR: The level spacing of quantized electronic states becomes fairly large in very fine particles as mentioned in this paper, and the thermal properties may show considerable deviations from the normal bulk values for such fine particles.
Abstract: The level spacing of quantized electronic states becomes fairly large in very fine particles. For instance, it will be comparable to k T at T =1°K if the linear dimension of a particle is 50 A or so. Thermal properties may show considerable deviations from the normal bulk values for such fine particles. The heat capacity will be reduced to about two-thirds and the paramagnetic susceptibility may be enhanced. Even more important effects are expected for relaxation processes. They are discussed briefly, but more detailed treatments will be given in a forth-coming paper.
876 citations
TL;DR: An in situ X-ray diffraction observation of a liquid–liquid transition in phosphorus, involving an abrupt, pressure-induced structural change between two distinct liquid forms, strongly suggestive of a first-order liquid– liquid phase transition.
Abstract: First-order structural phase transitions are common in crystalline solids, whereas first-order liquid-liquid phase transitions (that is, transitions between two distinct liquid forms with different density and entropy) are exceedingly rare in pure substances But recent theoretical and experimental studies have shown evidence for such a transition in several materials, including supercooled water and liquid carbon Here we report an in situ X-ray diffraction observation of a liquid-liquid transition in phosphorus, involving an abrupt, pressure-induced structural change between two distinct liquid forms In addition to a known form of liquid phosphorus--a molecular liquid comprising tetrahedral P4 molecules--we have found a polymeric form at pressures above 1 GPa Changing the pressure results in a reversible transformation from the low-pressure molecular form into the high-pressure polymeric form The transformation is sharp and rapid, occurring within a few minutes over a pressure range of less than 002 GPa During the transformation, the two forms of liquid coexist These features are strongly suggestive of a first-order liquid-liquid phase transition
719 citations
TL;DR: Suspended gold nanowires were made in an ultra-high vacuum and shown to have a multi-shell structure composed of coaxial tubes, resulting in magic shell-closing numbers.
Abstract: Suspended gold nanowires were made in an ultra-high vacuum. The finest of them was 0.6 nanometer in diameter and 6 nanometers in length. By high-resolution electron microscopy, they were shown to have a multi-shell structure composed of coaxial tubes. Each tube consists of helical atom rows coiled round the wire axis. The difference between the numbers of atom rows in outer and inner shells is seven, resulting in magic shell-closing numbers.
674 citations
TL;DR: A multiply twinned particle model is proposed by the present author, and the appearance of the 111 spots and the dark field image contrasts can satisfactorily be explained by this model.
Abstract: The orientation and structure of gold particles formed by evaporation on rocksalt cleaved in ultrahigh vacuum have been studied at various stages of the nucleation and growth process. Besides four 200 and twenty-four 220 spots which indicate the presence of the (001) orientation and (111) orientation respectively, twenty-four abnormal 111 spots have been observed in electron diffraction patterns taken at earlier stages of growth, and various unusual contrasts have been observed in dark field electron micrographs using one of 111 spots. A multiply twinned particle model is proposed by the present author, and the appearance of the 111 spots and the dark field image contrasts can satisfactorily be explained by this model. With increasing thickness particles with the (111) orientation and without the multiple twinning exclusively grow up, while multiply twinned particles and those with the (001) orientation seem to stop their growth; and a continuous gold film with the (111) fibrous structure is formed at a t...
465 citations