Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session U53: Synthesis and Characterizations Large Scale of 2D Materials II |
Hide Abstracts |
Sponsoring Units: DMP Chair: Robert Hovden Room: Mile High Ballroom 1F |
Thursday, March 5, 2020 2:30PM - 2:42PM |
U53.00001: Atomic resolution characterization of 2D materials with scanning transmission electron microscopy. Invited Speaker: Nasim Alem Selected by Focus Topic Organizer (Liuyan Zhao, Robert Hovden). |
Thursday, March 5, 2020 2:42PM - 2:54PM |
U53.00002: Using Intercalation Chemistry to Change Interlayer Spacing and Resulting Bandgap of Two-Dimension Materials Andrew Smith, Subash Kattel, Zachary Hecht, Henry Wladkowski, Joseph R Murphy, WIlliam Rice, Elliott Hulley, John Ackerman, Brian Leonard The operating principle behind smart windows is that they can transmit, absorb or reflect different wavelengths of light at will. To achieve these properties, they must be constructed with materials that have an easily tunable bandgap, this is often done via intercalation chemistry. 2D materials have shown similar tunablity in the past and often show enhanced mobility for ions. We are exploring one such material, WO2Cl2, and what role interlayer spacing plays in the bandgap of 2D materials. When WO2Cl2 is intercalated with Li, it starts as a wide bandgap material (clear) then transitions to a blue narrower bandgap material, then a coppery metallic phase. To understand these phases, we have carried out 4-point resistivity measurements, absorption and Raman spectroscopy, XRD, XPS, SEM, and TEM. These methods have shown intercalated WO2Cl2 to be a very tunable and versatile material. Additionally, we hypothesize a direct relationship between bandgap, interlayer spacing and ion size for WO2Cl2. To test this, we have examined properties of WO2Cl2 that has been intercalated ions of increasing size, Li<Na<K<Rb<Cs to great success. |
Thursday, March 5, 2020 2:54PM - 3:06PM |
U53.00003: Realization of 2D Crystalline Metal Nitrides via Selective Atomic Substitution Jun Cao, Tianshu Li, Hongze Gao, Xi Ling Two-dimensional (2D) transition metal nitrides (TMNs) are emerging members in 2D family with promising potential for a range of applications. Their applications can be further extended to electronic and optoelectronic devices through the acquisition of high crystalline and large-area thin films. However, materials that meet such requirements have not been achieved using previous methods. Here, we report the synthesis of few-nanometer thin Mo5N6 crystals with satisfactory area and quality via chemical conversion of layered MoS2 crystals. The lateral dimensions of Mo5N6 crystals are inherited from the MoS2 precursors. Atomic force microscopy characterization indicates that the thicknesses of Mo5N6 crystal reduce to about 1/3 of the MoS2 crystal, matching well with the crystal structure model. Electrical measurement shows the high conductivity of Mo5N6. In addition, this chemical conversion strategy is found versatile for the synthesis of various metal nitrides including W5N6, and TiN using corresponding metal sulfides. Our strategy offers a new direction for preparing 2D TMNs with desired characteristics, opening a door for future exploration of fundamental physics and devices applications. |
Thursday, March 5, 2020 3:06PM - 3:18PM |
U53.00004: Step edge-mediated assembly of periodic arrays of long graphene nanoribbons on Au(111) Wenchang Lu, Chuanxu Ma, Zhongcan Xiao, Jingsong Huang, Kunlun Hong, An-Ping Li, Jerry Bernholc
|
Thursday, March 5, 2020 3:18PM - 3:30PM |
U53.00005: Preparation and growth of sulfide heterostructure thin films from designed precursors Dennice Roberts, Brian Gorman, John Perkins, Andriy Zakutayev, Sage Bauers Design of chalcogenide heterostructures has enabled access to a remarkable range of material properties occuring as a result of structural flexibility at the nanoscale. A powerful approach to generating heterostructures involves the preparation of an amorphous precursor film designed to mimic the desired end product. While this has been highly successful in generating selenium-based heterostructures with novel properties, sulfur-based compounds have remained unexplored. Here we present the first crystalline sulfide heterostructure prepared using this precursor approach, forming superlattices with a tunable number of SnS layers sandwiched between monolayers of TaS2. Structural measurements confirm film crystallinity and overall film smoothness, and architecture is confirmed by high resolution TEM and EDS that resolves atomically precise sequencing of SnS and TaS2 layers. Formation mechanisms are assessed in terms of mobility of precursor elements upon heating. A path towards sulfide heterostructures with adjustable stacking orders allows the development of materials with precisely tuned properties that utilize phenomenon inherent in constituent compounds; such materials are promising for applications in advanced electronics. |
Thursday, March 5, 2020 3:30PM - 3:42PM |
U53.00006: Experimental demonstration of partial van der Waals screening by mono- and double-layer MoSe2 and MoS2 Stanislav Tsoi, Saujan V Sivaram, Matthew Rosenberger, Kathleen McCreary, Hsun-Jen Chuang, Berend Thomas Jonker Few-layer flakes of MoS2 or MoSe2 with lateral dimensions over 1 µm were grown on graphite using chemical vapor deposition, yielding layered samples MoS2/graphite or MoSe2/graphite, respectively. Next, an attractive van der Waals (vdW) force on a sharp AFM tip was measured from graphite, MoS2/graphite and MoSe2/graphite as a function of a separation between the tip and sample. The vdW force from the layered samples is significantly weaker than from graphite alone, suggesting screening of the semimetallic graphite by the semiconducting MoS2 and MoSe2. Statistical analysis over 6 different measurements indicates that the single-layer MoSe2 screens 59 ± 14 % and the single-layer MoS2 71 ± 12 % of the force from graphite. The double-layer samples exhibit even stronger screening, with the double-layer MoSe2 screening 77 ± 24 % and the double-layer MoS2 94 ± 8 %of the vdW force from graphite. The observed results demonstrate a possibility to engineer and control the nanoscale vdW forces in a bottom-up approach, and provide a critical experimental platform for testing the quantum electrodynamic Lifshitz theory of vdW interactions. |
Thursday, March 5, 2020 3:42PM - 3:54PM |
U53.00007: Graphene growth on non-metallic substrates by Chemical Vapor Deposition Sandra Rodriguez Villanueva, Alvaro Instan, Frank Mendoza, Brad R Weiner, Ram Katiyar, Gerardo Morell The electrical properties of graphene on dielectric substrates have many applications. Graphene is usually grown on metallic substrates then transferred onto dielectric substrates as necessary. However, to obtain graphene directly on non-metallic substrates is still challenging. In this work, we show the direct synthesis of graphene on SiO2/Si and SiC by hot-filament chemical vapor deposition. The graphene deposition was conducted at low pressures with a mixture methane in hydrogen and a substrate temperature 900°C followed by abrupt cooling to room temperature. A thin strip of copper layer was sputtered in the middle of the SiO2/Si substrates as a catalytic material. For the SiC substrate, a hydrofluoric acid treatment was used before graphene deposition. The structural properties of the graphene films were analyzed using Raman Spectroscopy, Atomic Force Microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Raman mapping and AFM measurements indicate the growth of few-layer graphene films in all cases. X-ray photoelectron spectroscopy confirmed the presence of graphene deposition on SiO2/Si and SiC substrates. The results show that the availability of copper vapors from the thin copper strip enables the growth of graphene in all surfaces of the non-metallic substrates. |
Thursday, March 5, 2020 3:54PM - 4:06PM |
U53.00008: Direct growth of twisted bilayer graphene with controllable twist angle by plasma-enhanced chemical vapor deposition Jiaqing Wang, Yen-Chun Chen, Wei-Hsiang Lin, Wei-Shiuan Tseng, Chii-Dong Chen, Yu-Shu Wu We report a direct plasma-enhanced chemical vapor deposition (PECVD) method to grow single crystalline bilayer graphene (BLG) flakes and mm-size BLG films with the interlayer twist angle controlled by the growth parameters.1 The average twist angle can be controlled from 0° to approximately 20° by tuning the CH4-to-H2 pressure ratio (PCH4/PH2). Raman spectroscopic studies on our PECVD-grown BLG together with x-ray and ultraviolet-light photoelectron spectroscopy indicate high-quality samples and reveal twist-angle dependent spectral characteristics. Atomically resolved scanning tunneling microscope (STM) is employed to identify the Moiré pattern and the value of the corresponding twist angle between two layers. Our PECVD-grown BLG provides a perfect platform to study the twist-angle dependence of its electronic properties. We performed transport measurements on our BLG samples with twist angles varying between 0° and 20°. The electronic properties of BLG of different twist angles are systematically investigated as a function of temperature and gate voltage, which provides useful information for the origin of various correlated phenomena. |
Thursday, March 5, 2020 4:06PM - 4:18PM |
U53.00009: 2D platinum diselenides grown on 3D wide-bandgap substrates by Van der Waals epitaxy Chia-Her Lin, Edward Stockert, Ching-Wen Chang, Ting Chen, Chien-Chen Kuo, Yi-Ying Lu, Li-Wei Tu, Quark Chen, Paritosh V Wadekar PtSe2 is a 2D material that undergoes phase transition from a semiconductor of Eg≈0.3 eV ∼ 1.4 eV to a type-II Dirac semimetal as its thickness varies. 3D wide band gap semiconductors continue to gain wider acceptance as a substrate material and as an electrode if properly doped. To embrace for broader applications, tractable materials process design rules are essential, especially in understanding the relationships between the Van der Waals epitaxy and the resulted physical properties of the ended products. In this work, ultrathin films of Pt were first deposited by magnetron sputtering on the GaN, AlN and Al2O3 substrates followed by atmospheric pressure chemical vapor deposition (APCVD). Selenization of the Pt films forms uniform and smooth 2D/3D selenide heterostructures. The effects of deposition parameters with respect to the underlying substrates according to the physical properties are investigated. Various spectroscopic means were used to study the samples with well characterized structural properties. |
Thursday, March 5, 2020 4:18PM - 4:30PM |
U53.00010: Facile Production of Macroscopic Single Crystal Monolayers and Artificial Lattices of 2D van der Waals Materials Fang Liu, Wenjing Wu, Yusong Bai, Sanghoon Chae, Qiuyang Li, Jue Wang, James C Hone, Xiaoyang Zhu Two dimensional (2D) materials from layered van der Waals (vdW) crystals hold great promises for electronic, optoelectronic, and quantum devices, but technological implementation has been hampered by the lack of high-throughput techniques for the production of monolayers with sufficient sizes and quality. Here we report a facile method to disassemble vdW single crystals layer-by-layer into monolayers with near-unity yield and with macroscopic dimensions limited only by bulk crystal sizes. The quality of the macroscopic single crystal monolayers are comparable to those of microscopic dimensions obtained from state-of-the-art techniques. We exfoliate a range of vdW crystals and assemble the monolayers into artificial lattices, including transition metal dichalcogenides with dramatic enhancement in nonlinear optical responses. This approach takes us one step closer to commercialization of 2D materials. |
Thursday, March 5, 2020 4:30PM - 4:42PM |
U53.00011: Automated Vacuum Stacking for Additive Assembly of 2D van der Waals Heterostructures Andrew Ye, Andrew J Mannix, Fauzia Mujid, Chibeom Park, Jiwoong Park Wafer-scale synthesis of monolayer 2D materials (2DMs) address the stochastic, small-area limitations of micromechanical exfoliation. Using wafer-scale synthesized 2D semiconductors along with large-area patterning and multi-functional polymer stamps, we demonstrate a highly automated, dry-transfer, additive assembly process. Our high-vacuum system can assemble 2D heterostructures at the precision of actuator limits (few micron lateral/0.2° rotational). Identical structures have been assembled in parallel and stacks of high layer counts (25+) have been achieved, all without active user control of the system. Fabricated heterostructures include a range of 2DMs (MoS2, WS2, WSe2, graphene) and metal electrodes (Au, Ti), and can be deposited onto a variety of substrates (SiO2, Al2O3, 2DMs). We also demonstrate controlled twisted n-layer heterostructure assembly, where number of layers depends on area limits of single-crystal 2DMs growth. |
Thursday, March 5, 2020 4:42PM - 4:54PM |
U53.00012: Impact of thermal treatment on graphene films synthesized via interfacial trapping technique Sara Chahid, Rajendra Dulal, Serafim Teknowijoyo, Alexander Rzhevskii, Armen Gulian Large variety of graphene applications in science and technology justify different methods to obtain pure graphene films. Among these methods, Woltornist et.al., ACS Nano 7, 7062 (2013) obtained promising results by pulverizing ultrapure graphite in water/n-heptane mixture to form continuous films on glass substrate. We report here subsequent steps of studying this method with different substrates and also of application of annealing (100o-600o, in air and in a vacuum) on the physical properties of these films. As can be deduced from Raman spectra, the quality of graphene films is enhanced in certain temperature range. We complemented Raman mapping by characterizing the morphology of films using scanning electron microscopy. Other instrumentation techniques have also been used to affect and study the physical properties of these films. Overall, the simplicity of the method and the quality of the film reveal potential areas of applications in microelectronics. |
Thursday, March 5, 2020 4:54PM - 5:06PM |
U53.00013: Fabrication and Imaging of Monolayer Phosphorene with Preferred Edge Configurations via Graphene-Assisted Layer-by-Layer Thinning Yangjin Lee, Sol Lee, Jun-Yeong Yoon, Jinwoo Cheon, Hu Young Jeong, Kwanpyo Kim Phosphorene, a monolayer of black phosphorus (BP), is an elemental 2D material with interesting physical properties including high charge carrier mobility and exotic in-plane anisotropic properties. To fundamentally understand its various physical properties, the atomic-scale structural investigation, various defect and preferred edge configurations for monolayer counterpart, is of critically importance. However, it has been challenging to perform imaging of monolayer phosphorene due to technical difficulty to prepare high-quality samples and damages induced during measurements via photons or high-energy electrons. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700