Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session P36: Synthesis and Properties of 2D Materials Beyond Graphene and TMD |
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Sponsoring Units: DMP Chair: Lain-Jong Li, KAUST Room: LACC 410 |
Wednesday, March 7, 2018 2:30PM - 2:42PM |
P36.00001: Abstract Withdrawn
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Wednesday, March 7, 2018 2:42PM - 2:54PM |
P36.00002: Chemical Vapor Deposition of Large-area 2D Hexagonal Diamond Ying Liu, Jinglei Ping, Wei Tan, Alan Johnson Hexagonal diamond, or lonsdaleite, is an allotrope of sp3 carbon with a hexagonal lattice that has only been prepared in bulk form with thickness above micrometer level. Here we report the first synthesis of uniform hexagonal diamond nanometer-thick films, to our knowledge, in large area (> 10 μm) by chemical vapor deposition. Using atomic force microscopy, we demonstrated that the film is uniform with thickness of < 0.9 nm. X-ray photoelectron spectroscopy and Raman spectroscopy indicate that the film consists primarily of sp3 bonded carbon in diamond crystal structure with minimal sp2 bonding. The hexagonal structure was also confirmed with selected area diffraction performed in a transmission electron microscope. We demonstrated that the diamond film has a high elastic modulus comparable to graphene prepared by chemical vapor deposition. |
Wednesday, March 7, 2018 2:54PM - 3:06PM |
P36.00003: Preparation of Silicene by Plasma Enhanced Chemical Vapor Deposition Battogtokh Jugdersuren, Xiao Liu, James Culbertson, Nadeem Mahadik Silicene, one monolayer of silicon atoms, has attracted much attention due to its easily tunable band gap. Alternative methods for growing silicene are needed to replace current multi-step molecular-beam-epitaxy (MBE) process for potential large scale synthesis and application. Here, we report possibility of growing single and multilayer silicene by Plasma Enhanced Chemical Vapor Deposition (PECVD) method. This technique has the advantage to achieve deposition at a less stringent vacuum environment and with a few processing steps. Analysis of Raman spectroscopy, X-ray diffraction, and X-ray photon electron spectroscopy studies of PECVD silicene will be discussed. |
Wednesday, March 7, 2018 3:06PM - 3:18PM |
P36.00004: Abstract Withdrawn
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Wednesday, March 7, 2018 3:18PM - 3:30PM |
P36.00005: Many-body quantum Monte Carlo study of single-layer phosphorene: cohesion and band gap Tobias Frank, Rene Derian, Lubos Mitas, Jaroslav Fabian, Ivan Stich Phosphorene is perhaps the most promising member of the family of two-dimensional (2D) materials with unique and tunable electronic and photonic properties combined with high carrier mobility. The direct band gap is tunable over the visible to near infrared range by changing the number of layers, straining, or alloying to cover the technologically important applications. However, due to experimental limitations such as presence of substrates, capping layers, defects, etc. and available accuracy of the mainstream modeling techniques, the a la carte property tuning for device applications is hampered by absence of accurate and unbiased data on even the simplest systems, such as the free-standing unstrained single-layer phosphorene. By determining the benchmark value of the fundamental gap in single-layer phosphorene to be 2.40+/-0.17 from cluster calculations and 2.68+/-0.10 eV from periodic supercell model using explicitly correlated quantum Monte Carlo (QMC) methods we provide one of the key missing links. We also predict the cohesion of the phosphorene layer as 3.194+/-0.025 eV/atom. |
Wednesday, March 7, 2018 3:30PM - 3:42PM |
P36.00006: Formation of quasi two-dimensional allotropes of phosphorus on metal substrates Daniel Hashemi, Gene Siegel, Michael Snure, Stefan Badescu Quasi 2D phosphorous in phosphorene (black-P) and blue-phosphorous (blue-P) forms are receiving an increased interest for their potential in flexible and tunable electronics. Recently, the synthesis of blue-P was demonstrated on transition metal or alloy surfaces, with black-P not grown epitaxially on any substrate to date. Our experiments confirm that the high phosphorus vapor pressure and reactivity lead mostly to the formation of metal phosphides or amorphous phosphorous with a narrow window for blue-P. Modeling efforts that assume black- and blue-P on Cu and Ag as final products show that blue-P is slightly favored by a bonding between the P-half layers that is stronger than the lower half layer-metal bond. Here, we investigate computationally the catalytic activity of various metal surfaces, which could potentially enable a stronger bonding of the lower layer. The phosphorus adsorbates have a large effect on the metal atoms which they are closest to, and strong hybridization between the p orbitals of phosphorous and d orbitals of the substrate is found, suggesting a strong coupling. Besides its impact on the material properties and possible applications, this provides a way to gain insight into the controlled formation of the allotropes of phosphorous on the metal surfaces. |
Wednesday, March 7, 2018 3:42PM - 3:54PM |
P36.00007: Abstract Withdrawn
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Wednesday, March 7, 2018 3:54PM - 4:06PM |
P36.00008: Revisiting the energy barrier of black phosphorous and monochalcogenide monolayers Shiva Poudel, Thaneshwor Kaloni, Salvador Barraza-Lopez The energy barrier is the energy required to change the rectangular unit cell of black phosphorene or monochalcogenide monolayers onto a square unit cell. Here, three different DFT codes were employed to obtain these barriers. It is known that the energy barrier decreases with the increase of the average atomic number [1], but in calculations performed with van der Waals corrections, the barrier is higher than our previously reported values. Also, we found that the ionicity, which is related to the average atomic number [2], has a linear relation with the energy barrier. |
Wednesday, March 7, 2018 4:06PM - 4:18PM |
P36.00009: Liquid phase mass production of air-stable black phosphorus/phospholipids nanocomposite with ultralow tunneling barrier Yi-Nan Liu, Qiankun Zhang, Jiawei Lai, Shaomian Qi, Chunhua An, Yao Lu, Xuexin Duan, Wei Pang, Daihua Zhang, Dong Sun, Jianhao Chen, Jing Liu Few-layer black phosphorus (FLBP), has attracted substantial attention due to its great potential in electronic and optoelectronic applications. However, reactivity of FLBP flakes with ambient species limits its direct applications. Among various methods to passivate FLBP in ambient environment, nanocomposites mixing FLBP flakes with stable matrix may be one of the most promising approaches for industry applications. Here, we report a simple one-step procedure to mass produce air-stable FLBP/phospholipids nanocomposite in liquid phase. The resultant nanocomposite is found to have ultralow tunneling barrier for electrons which can be described by an Efros-Shklovskii variable range hopping mechanism. Devices made from such mass-produced FLBP/phospholipids nanocomposite show highly stable electrical conductivity and opto-electrical response in ambient conditions, indicating its promising applications in both electronic and optoelectronic applications. This method could also be generalized to the mass production of nanocomposites consisting of other air-sensitive two-dimensional materials, such as FeSe, NbSe2, WTe2, etc. |
Wednesday, March 7, 2018 4:18PM - 4:30PM |
P36.00010: Formation of planar stanene epitaxially grown on Ag(111) Junji Yuhara, Yuya Fujii, Kazuki Nishino, Naoki Isobe, MAsashi Nakatake, Lede Xian, Angel Rubio, Guy Le Lay The heavy group 14 elements (Si, Ge, Sn) have received great attention as candidates of post-graphene materials [1-3]. Recently, the synthesis of Sn-based highly buckled stanene on Bi2Te3(111) has been reported [3]. In the present study, we report a planar stanene prepared on Ag(111), which we have investigated using combined experimental techniques and ab initio calculations. The high-resolution STM images clearly exhibit large area planar stanene with honeycomb structure. From PES spectra, it is identified that Ag 3d5/2 exhibits a new component at higher binding energy than for the initially formed Ag2Sn surface alloy. The Sn 4d spectra exhibit a single component for the Ag2Sn alloy and two specific components for stanene grown on Ag(111). A parabolic electronic band is observed in the ARPES measurements. This electronic signature is rather consistently reproduced in the band structure of stanene on Ag(111) calculated using DFT calculations. These results establish that planar stanene, potentially a room temperature topological insulator, is formed on Ag(111) substrate. |
Wednesday, March 7, 2018 4:30PM - 4:42PM |
P36.00011: Realization of Vanadium Sulfide Compounds in the 2D Limit Charlotte Sanders, Fabian Arnold, Raluca Stan, Albert Bruix, Sanjoy Mahatha, Henriette Lund, Maciej Dendzik, Davide Curcio, Harsh Bana, Elisabetta Travaglia, Luca Bignardi, Paolo Lacovig, Daniel Lizzit, Marco Bianchi, Jill Miwa, Martin Bremholm, Silvano Lizzit, Philip Hofmann By comparison with many of the layered transition metal dichalcogenides, VS2 has been relatively understudied, likely because it is a challenging material to prepare stoichiometrically in the bulk. Moreover, the single layer has not heretofore been isolated. However, the material has intriguing properties in the bulk, including both charge density waves and magnetism. |
Wednesday, March 7, 2018 4:42PM - 4:54PM |
P36.00012: Ambipolar Transport Based on CVD-synthesized ReSe2 Byunggil Kang, Youngchan Kim, Changgu Lee Rhenium diselenide (ReSe2) is a member of 2D semiconducting materials with in-plane anisotropic electrical and optical properties. We report the electrical behaviors of ReSe2 synthesized via a chemical vapor deposition (CVD) method. Differently from previous reports on unipolar ReSe2 FETs, the synthesized-ReSe2 FETs have ambipolar characteristics when it contacts with gold electrode. This device shows high on/off current ratios over 104 for both of hole and electron. Moreover, there was little dependence of the behavior on the thickness. However, depending on the electrode metal, the main charge carrier type was changed. We measured the work function for synthesized ReSe2 in order to investigate the ambipolar characteristic using Kelvin probe force microscopy (KPFM). We also designed an inverter to study the feasibility of its application in logic circuits. Additionally, the atomic structure of the synthesized ReSe2, which has triclinic crystal system, was confirmed by transmission electron microscope (TEM), and the corresponding vibration modes were checked by Raman spectroscopy. |
Wednesday, March 7, 2018 4:54PM - 5:06PM |
P36.00013: The ionic versus metallic nature of 2D electrides: A density-functional description Stephen Dale, Erin Johnson The two-dimensional (2D) electrides are a highly unusual class of matierals, possessing interstitial electron layers sandwiched between cationic atomic layers of the solid. In this work, density-functional theory, with the exchange-hole dipole moment dispersion correction, is used to investigate exfoliation and interlayer sliding of the only two experimentally known 2D electrides: [Ca2N]+e− and [Y2C]2+(2e−). Examination of the valence states during exfoliation identifies intercalated electrons in the bulk and weakly-bound surface-states in the fully-expanded case. The calculated exfoliation energies for the 2D electrides are found to be much higher than for typical 2D materials, which is attributed to the ionic nature of the electrides and the strong Coulomb forces governing the interlayer interactions. Conversely, the calculated sliding barriers are found to be quite low, comparable to those for typical 2D materials, and are effectively unchanged by exclusion of dispersion. We conjecture that the metallic nature of the interstitial electrons allows the atomic layers to move relative to each other without significantly altering the interlayer binding. |
Wednesday, March 7, 2018 5:06PM - 5:18PM |
P36.00014: A Three-Dimensional Phase-Field Crystal Model for 2D Materials David Montiel, Guanglong Huang, Eli Alster, Peter Voorhees, Katsuyo Thornton We introduce a Phase-Field Crystal (PFC) model to simulate the growth of 2D materials in three dimensions. Our approach employs a set of two- and three-point correlation terms in the free energy functional that are designed to energetically favor structures with periodicity along a plane but are localized in the direction perpendicular to that plane. We show how this method can be applied to stabilize several two-dimensional structures and to study three-dimensional effects, such as buckling due to defects. This will allow us to examine how specific defects such as vacancies and grain boundaries affect growth of the layer and the resulting mechanical properties. Finally, we present examples of how our model can be adapted to study monolayers and multilayers, as well as their interactions with a substrate. |
Wednesday, March 7, 2018 5:18PM - 5:30PM |
P36.00015: Tunable Electronic Properties in Molecular Graphene Esa Rasanen, Sami Paavilainen, Matti Ropo, Jouko Nieminen, Jaakko Akola We uncover the electronic structure of molecular graphene [1] produced by adsorbed CO molecules on a copper (111) surface by means of first-principles (density-functional theory) calculations [2]. Our results show that the band structure is fundamentally different from that of conventional graphene, and the unique features of the electronic states arise from co-existing honeycomb and Kagome symmetries. Furthermore, the Dirac cone does not appear at the K-point but at the Γ-point in the reciprocal space, and it is accompanied by a third, almost flat band. Calculations of the surface structure with Kekulé distortion show a gap opening at the Dirac point in agreement with experiments. Finally, we use our computational approach to assess the feasibility of the system as an electronic Lieb lattice according to recent experiments [3]. |
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