A new series of two-dimensional silicon crystals with versatile electronic properties

Abstract

Silicon (Si) is one of the most extensively studied materials owing to its significance to semiconductor science and technology. While efforts to find a new three-dimensional (3D) Si crystal with unusual properties have made some progress, its two-dimensional (2D) phases have not yet been explored as much. Here, based on a newly developed systematic ab initio materials searching strategy, we report a series of novel 2D Si crystals with unprecedented structural and electronic properties. The new structures exhibit perfectly planar outermost surface layers of a distorted hexagonal network with their thicknesses varying with the atomic arrangement inside. Dramatic changes in electronic properties ranging from semimetal to semiconducting with indirect energy gaps and even to one with direct energy gaps are realized by varying thickness as well as by surface oxidation. Our predicted 2D Si crystals with flat surfaces and tunable electronic properties will shed light on the development of silicon-based 2D electronics technology.

Deformed octagon-hexagon-square structure of group-IV and group-V elements and III-V compounds

“…The growth of multilayer silicene up to ∼100 layers [13] has led to an important question of whether Si can have a layered structure like graphene [14,15]. Stable trigonal and honeycomb dumbbell structures, which were deduced to understand grown silicene [12,16,17], initiated different types of silicon single-layers [18][19][20][21][22][23][24]. A similar dumbbell patterned monolayer has been predicted also for germanene [16].…”

“…The dumbbell structure of Si is further exploited by Borlido et al [19] to predict a low-energy, 2D semiconducting structure of Si by combining the silicene honeycomb structure with the dumbbell atoms arranged in a zigzag pattern. In another study [20], unprecedented 2D ultrathin Si structures were generated by ab initio materials searching study with electronic properties ranging from semimetal to semiconductor. These structures had perfectly planar outermost surface made by distorted hexagonal rings and thickness depending on the arrangements of tetrahedron between these surfaces.…”

A New Family of Two-Dimensional Crystals: Open-Framework T3X (T = C, Si, Ge, Sn; X = O, S, Se, Te) Compounds with Tetrahedral Bonding

“…Recently, we developed a new CSP method particularly suited for 2D systems [11]: Search by Ab initio Novel Design via Wyckoff positions Iteration in Conformational Hypersurface (SANDWICH). In this new method, the 2D crystals are constructed by joining both top and bottom surface layers while the space between the surface layers is filled with bridge atoms [11]. The inner part is constructed by exhaustive enumeration of a subset of the Wyckoff positions corresponding to the space group determined by the surface layers.…”

Ab initio quantum transport in AB-stacked bilayer penta-silicene using atomic orbitals

“…Other forms of silicon derivatives have been the focus of studies using systematic materials search, revealing novel allotropes with direct band-gaps [14] and even high mobility values [15]. Penta-silicene is a new form of monolayer silicon that has been observed recently [16,17].…”