Phase Engineering of Epitaxial Stanene on a Surface Alloy.

Stanene is a notable two-dimensional topological insulator with a large spin-orbit-coupling-induced band gap. However, the formation of surface alloy intermediates during the epitaxial growth on noble metal substrates prevents the as-grown stanene from preserving its intrinsic electronic states. Here, we show that an intentionally prepared 3×3Au2Sn(111) alloy surface is a suitable inert substrate for growing stanene without the further formation of a complicated surface alloy by scanning tunneling microscopy. The Sn tetramer and clover-shaped Sn pentamer are intermediates for the black-phosphorene-like Sn film at a substrate temperature of <420 K, which transforms to a blue-phosphorene-like stanene with a lattice constant of 0.50 nm above 500 K. First-principles calculations reveal that the epitaxial Sn layer exhibits a lattice registry growth mode and holds a direct energy gap of ∼0.4 eV. Furthermore, interfacial charge-transfer-induced significant Rashba splitting in its electronic structure gives it great potential in spintronic applications.

Advance in Close-Edged Graphene Nanoribbon: Property Investigation and Structure Fabrication.

The absence of dangling bonds in close-edged graphene nanoribbons (CEGNRs) confers upon them a series of fascinating properties, especially when compared with cylindrical carbon nanotubes and open-edged GNRs. Here, the configuration of CEGNRs is described, followed by the structure-related properties, including mechanical, thermal, electrical, optical, and magnetic properties. Based on the unique structures and extraordinary properties, their potential applications in a variety of fields, such as field-effect transistors, energy suppliers, nanoactuators, and fibers, are discussed. Remarkably, the strategies applied for generating CEGNRs, mainly from the collapse of carbon nanotubes and graphene tubes, are depicted in detail. Finally, the prospects in the research area of CEGNRs are proposed.

Designing Catalysts for Chirality-Selective Synthesis of Single-Walled Carbon Nanotubes: Past Success and Future Opportunity.

A major obstacle for the applications of single-walled carbon nanotubes (SWNTs) in electronic devices is their structural diversity, ending in SWNTs with diverse electrical properties. Catalytic chemical vapor deposition has shown great promise in directly synthesizing high-quality SWNTs with a high selectivity to specific chirality (n, m). During the growth process, the tube-catalyst interface plays crucial roles in regulating the SWNT nucleation thermodynamics and growth kinetics, ultimately governing the SWNT chirality distribution. Starting with the introduction of SWNT growth modes, this review seeks to extend the knowledge about chirality-selective synthesis by clarifying the energetically favored SWNT cap nucleation and the threshold step for SWNT growth, which describes how the tube-catalyst interface affects both the nucleus energy and the new carbon atom incorporation. Such understandings are subsequently applied to interpret the (n, m) specific growth achieved on a variety of templates, such as SWNT segments or predefined molecular seeds, transition metal (Fe, Co and Ni)-containing catalysts at low reaction temperatures, W-based alloy catalysts, and metal carbides at relatively high reaction temperatures. The up to date achievements on chirality-controlled synthesis of SWNTs is summarized and the remaining major challenges existing in the SWNT synthesis field are discussed.