Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 20Citation - Scopus: 23Kagome-Like Silicene: a Novel Exotic Form of Two-Dimensional Epitaxial Silicon(Elsevier, 2020) Sassa, Yasmine; Johansson, Fredrik O. L.; Lindblad, Andreas; Yazdi, Milad G.; Simonov, Konstantin; Weissenrieder, Jonas; Le Lay, Guy; İyikanat, Fadıl; Şahin, HasanSince the discovery of graphene, intensive efforts have been made in search of novel two-dimensional (2D) materials. Decreasing the materials dimensionality to their ultimate thinness is a promising route to unveil new physical phenomena, and potentially improve the performance of devices. Among recent 2D materials, analogs of graphene, the group IV elements have attracted much attention for their unexpected and tunable physical properties. Depending on the growth conditions and substrates, several structures of silicene, germanene, and stanene can be formed. Here, we report the synthesis of a Kagome-like lattice of silicene on aluminum (1 1 1) substrates. We provide evidence of such an exotic 2D Si allotrope through scanning tunneling microscopy (STM) observations, high-resolution core-level (CL) and angle-resolved photoelectron spectroscopy (ARPES) measurements, along with Density Functional Theory calculations.Article Citation - WoS: 3Citation - Scopus: 2?-Silicene as Oxidation-Resistant Ultra-Thin Coating Material(Beilstein-Institut Zur Forderung der Chemischen Wissenschaften, 2017) Kandemir, Ali; İyikanat, Fadıl; Bacaksız, Cihan; Şahin, HasanBy performing density functional theory (DFT)-based calculations, the performance of a-silicene as oxidation-resistant coating on Ag(111) surface is investigated. First of all, it is shown that the Ag(111) surface is quite reactive against O atoms and O2 molecules. It is known that when single-layer silicene is formed on the Ag(111) surface, the 3 × 3-reconstructed phase, a-silicene, is the ground state. Our investigation reveals that as a coating layer, a-silicene (i) strongly absorbs single O atoms and (ii) absorbs O2 molecules by breaking the strong O-O bond. (iii) Even the hollow sites, which are found to be most favorable penetration path for oxygens, serves as high-energy oxidation barrier, and (iv) α-silicene becomes more protective and less permeable in the presence of absorbed O atom. It appears that single-layer silicene is a quite promising material for ultra-thin oxidation-protective coating applications.Book Part Citation - WoS: 6Citation - Scopus: 5Strain engineering of 2D materials(Springer Verlag, 2017) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, AngelWhen bulk structures are thinned down to their monolayers, degree of orbital interactions, mechanical properties and electronic band dispersion of the crystal structure become highly sensitive to the amount of applied strain. The source of strain on the ultra-thin lattice structure can be (1) an external device or a flexible substrate that can stretch or compress the structure, (2) the lattice mismatch between the layer and neighboring layers or (3) stress induced by STM or AFM tip.Book Part Citation - WoS: 7Citation - Scopus: 10Germanene, Stanene and Other 2d Materials(Springer Verlag, 2017) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, AngelGermanene and stanene (also sometimes written stannene or called tinene) are 2D materials composed of germanium and tin atoms respectively arranged in a honeycomb structure similarly to graphene and silicene. The atomic structure of freestanding germanene and stanene is buckled like in the case of silicene (see Figure 2.4DFT calculations (Kresse and Joubert, Phys Rev B 59:1758-1775, 1999) performed by projector augmented wave (PAW) method (BlÖchl, Phys Rev B 50:17953-17979, 1994) and adopting PBE functional (Perdew et al. Phys Rev Lett 77:3865-3868, 1996) result in a lattice constants 4.06 and 4.67Å and buckling heights of 0.69 and 0.85Å for germanene and stanene respectively.Book Part Citation - Scopus: 1Multilayer Silicene(Springer Verlag, 2017) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, AngelSilicon does not have a naturally occurring layered allotrope like graphite. However, it is possible to grow monolayer silicene on substrates, as we have seen in Chap. 3. Extending this idea further, one may wonder whether it is possible to synthesize layered silicon structures by continuing the growth started as a monolayer silicene. In this chapter we discuss the experimental and theoretical works that are based on this idea of multilayer silicene growth.Book Part Citation - WoS: 1Citation - Scopus: 2Silicene on Ag Substrate(Springer Verlag, 2017) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, AngelThe isolation of graphene sheets from its parent crystal graphite has given the kick to experimental research on its prototypical 2D elemental cousin, silicene (Brumfiel 2013). Unlike graphene, silicene lacks a layered parent material from which it could be derived by exfoliation, as mentioned in Chap. 2. Hence, the efforts of making the silicene dream a reality were focused on epitaxial growth of silicene on substrates. The first synthesis of epitaxial silicene on silver (111) (Vogt et al. 2012; Lin et al. 2012) and zirconium diboride templates (Fleurence et al. 2012) and next on an iridium (111) surface (Meng et al. 2013), has boosted research on other elemental group IV graphene-like materials, namely, germanene and stanene (Matthes et al. 2013; Xu et al. 2013). The boom is motivated by several new possibilities envisaged for future electronics, typically because of the anticipated very high mobilities for silicene and germanene (Ye et al. 2014), as well as potential optical applications (Matthes et al. 2013). It is also fuelled by their predicted robust 2D topological insulator characters (Liu et al. 2011; Ezawa 2012) and potential high temperature superconductor character (Chen et al. 2013; Zhang et al. 2015). One of the most promising candidates as a substrate is Ag because from the studies of the reverse system, where Ag atoms were deposited on silicon substrate, it was known that Ag and silicon make sharp interfaces without making silicide compounds (Le Lay 1983). Indeed, studies on synthesis and characterization of silicene is mainly focused on using Ag(111) as substrates and hence we think it is important to understand this particular system. In this chapter, we present the experimental and theoretical studies investigating the atomic and electronic structure of silicene on Ag substrates.Book Part Citation - WoS: 5Citation - Scopus: 11Freestanding Silicene(Springer Verlag, 2017) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, AngelObtaining a freestanding 2D graphene flake is relatively easy because it has a naturally occurring 3D layered parent material, graphite, made up of graphene layers weakly bound to each other by van der Waals interaction. In fact, graphite is energetically more favorable than diamond (which is one of the most stable and hard materials on Earth) that is the sp3 hybridized allotrope of carbon. To prepare freestanding graphene, it is enough to come up with a smart procedure for isolating the weakly bound layers of graphite. The same is also true for other layered materials like hexagonal boron nitride, black phosphorus, metal dichalcogenides and oxides. Silicene, on the other hand, doesn’t have a naturally occurring 3D parent material since silicon atoms prefer sp3 hybridization over sp2 hybridization. This makes the synthesis of freestanding silicene very hard, if not impossible. However, it is possible to epitaxially grow silicene on metal substrates and make use of its intrinsic properties by transferring it to an insulating substrate (Tao et al. 2015). In this chapter, we focus on intrinsic properties of freestanding silicene in the absence of the metallic substrate.Book Part A Brief History of Silicene(Springer Verlag, 2017) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, AngelResearch on silicene shows a fast and steady growth that has increased our tool-box of novel 2D materials with exceptional potential applications in materials science. Especially after the experimental synthesis of silicene on substrates in 2012 it has attracted substantial interest from both theoretical and experimental communities. Every day, new people from various disciplines join this rapidly growing field. The aim of this book is to serve as a fast entry to the field to these newcomers and as a long-living reference to the growing community. To achieve this goal, the book is designed to emphasize the most crucial developments from both theoretical and experimental point of view since the starting of the silicene field back in 1994 with the first theoretical paper proposing the structure of silicene. We provide the general concepts and ideas such that the book is accessible to everybody from graduate students to senior researchers and we refer the reader interested in the detail to the relevant literature. We now start with a brief history of silicene where we highlight, in the chronological order, the important works that shaped our understanding of silicene.Article Citation - WoS: 1Citation - Scopus: 1Adsorption and Diffusion Characteristics of Lithium on Hydrogenated ?- and Ss-Silicene(Beilstein-Institut Zur Forderung der Chemischen Wissenschaften, 2017) İyikanat, Fadıl; Kandemir, Ali; Bacaksız, Cihan; Şahin, HasanUsing first-principles density functional theory calculations, we investigate adsorption properties and the diffusion mechanism of a Li atom on hydrogenated single-layer α- and β-silicene on a Ag(111) surface. It is found that a Li atom binds strongly on the surfaces of both α- and β-silicene, and it forms an ionic bond through the transfer of charge from the adsorbed atom to the surface. The binding energies of a Li atom on these surfaces are very similar. However, the diffusion barrier of a Li atom on H-α-Si is much higher than that on H-β-Si. The energy surface calculations show that a Li atom does not prefer to bind in the vicinity of the hydrogenated upper-Si atoms. Strong interaction between Li atoms and hydrogenated silicene phases and low diffusion barriers show that α- and β-silicene are promising platforms for Li-storage applications.