Is Graphitic Silicon Carbide (Silagraphene) Stable?

Abstract

Graphene is considered to be the most likely candidate for the postsilicon era; however, the problem with its zero band gap is challenging to overcome. A close relative of silicon, silicon carbide is expected to have a stable 2D polymorph which happens to be a wide-gap semiconductor. Unfortunately, the so-called silagraphene has proven to be elusive. To date, neither theoretical nor experimental studies have been conclusive. Here, we employ computational methods to determine the stable arrangements of silagraphene and establish their accurate band structure. We also experimentally validate our models by preparing and characterizing a number of graphitic features. Silagraphene exhibits a wide spectrum of optoelectronic properties (360–690 nm) as well as an unusual band structure with highly anisotropic transport properties, which originates from its nondispersive band near its K-point. This feature makes direct-indirect gap crossover extremely sensitive to ambient conditions, making silagraphene suitable for a range of sensors.

Graphitic SiC: A potential anode material for Na‐ion battery with extremely high storage capacity

“…To do so, various stacking modes of SiC layers are considered, including (i) a simple hexagonal stacking in which the Si/C atom is either on the top of Si/C atom or on the top of C/Si atom; (ii) Bernal-type hexagonal stacking, in which Si/C atom is either above the Si/C atom or above C/Si atom. As shown in Figure 1A, graphitic SiC prefers to form a Bernal-type hexagonal stacking structure which agrees with Yaghoubi et al's recent theoretical result [34]. In this graphitic SiC structure, the Si atoms in one SiC layer are located above Si atoms in the adjacent SiC layer.…”

“…In this graphitic SiC structure, the Si atoms in one SiC layer are located above Si atoms in the adjacent SiC layer. It is noted that the calculated interlayer distance of such graphitic SiC in our work (by using VASP package) is 3.53 Å, which is relatively smaller than that of Yaghoubi et al's result [34] (3.66 Å, by using CASTEP package) due to the different optimization methods.…”

“…Now, we would like to discuss the stability of graphitic SiC before and after the intercalation of Na ions. As have been mentioned in previous theoretical and experimental studies [34,40,41], graphitic SiC has proven to be an elusive material, which tends to change into the most stable tetrahedral SiC phase. To confirm this point, the molecular dynamics (MD) simulation was performed at room temperature, our results indicate that the Si and C atoms in adjacent SiC layer of graphitic SiC prefer to bond together, accompanied by the formation of the most stable tetrahedral SiC, which agrees with previous studies.…”

“…The electron‐ion interactions were described by using projection enhanced wave (PAW) [37]. For the exchange‐ correlation functional, the Perdew‐Burke‐Ernzerh revised for solids (PBEsol) version of the generalized gradient approximation (GGA) [38] was used according to previous theoretical study on graphitic SiC [34]. The graphitic SiC model used in this work was constructed by using 2 × 2 supercell structure.…”

“…So far, over 250 polytypes of SiC have been identified, while the fabrication of SiC multilayer structures is very difficult due to the its strong sp 3 preference [29]. Until recently, graphitic SiC with a few numbers of SiC layers stacking has been observed in experiment, which provides the possibility for the synthesis of pure graphitic SiC in the future [34]. Interestingly, the interlayer distance of such graphitic SiC (3.66 Å) is larger than that of Graphite (3.40 Å), which may be beneficial for the intercalation of Na ions.…”