Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session E13: 2D Materials (General) -- Growth, Mostly CVD/TFocus
|
Hide Abstracts |
Sponsoring Units: DMP DCOMP Chair: Kibum Kang Room: BCEC 153B |
Tuesday, March 5, 2019 8:00AM - 8:12AM |
E13.00001: Interaction of Two-Dimensional Transition Metal Dichalcogenides on Different Substrates and Nanostructures Andrew Greenspon, Qingqing Ji, Mena N Gadalla, Danqing Wang, Niamh Mulholland, Jing Kong, Evelyn L Hu Two-dimensional transition metal dichalcogenides (2D TMDs) are 2D semiconductors that hold promise for a variety of optoelectronic devices, especially by harnessing the valley degree of freedom. Growth of 2D TMDs on different substrates and nanostructures provides enormous opportunities in engineering ultra-thin devices with tailored optical emission properties. We characterize the optical differences when the 2D TMD molybdenum disulfide (MoS2) is grown via chemical vapor deposition on the substrates silicon dioxide on silicon, gallium nitride (GaN), and silicon carbide (SiC). Changes in the spacing and relative intensity of the E12g and A1g Raman peaks suggest differences in the microstructure of the grown MoS2 or its interaction with the substrate. Additionally, we characterize the interaction between MoS2 and optical cavities patterned onto GaN and SiC. Preliminary results show brighter MoS2 exciton photoluminescence and shifted emission peaks on the optical cavities compared to the bulk substrate of each. We also show first results attempting to couple MoS2 emission to the resonant modes of these optical cavities. |
Tuesday, March 5, 2019 8:12AM - 8:24AM |
E13.00002: The effect of multi-step Cu surface oxidization on growth of single crystal graphene by low pressure chemical vapor deposition Sajith Withanage, Tharanga Nanayakkara, Binuka Gunawardana, C. Rasadi Munasinghe, U. Kushan Wijewardena, Rasanga Samaraweera, Annika Kriisa, Ramesh Mani There has been much recent interest in the growth large area single crystal graphene flakes as an approach for overcoming the relatively low carrier mobility and the multigrain structure observed in Chemical Vapor Deposition (CVD) graphene. [1] One approach for growing large-sized single crystal graphene by CVD, [2] involves limiting the nucleation density of graphene on the copper foil surface that is often used as a catalyst for the growth of CVD graphene. Here, we report the results of a study of CVD growth of graphene following surface modification of the copper foil by oxidizing the copper foil at different stages of the growth process. Thus, we detail the effect of copper surface oxidization at different steps of the growth for controlling the nucleation on the size and the quality of relatively large sized single crystal graphene flakes. The graphene layers are characterized by various methods and the results of the study are reported. |
Tuesday, March 5, 2019 8:24AM - 8:36AM |
E13.00003: Tempered Dewetting of Metal Films: A platform for networked 2D crystal membranes Jose Fonseca Vega, James Clifford Culbertson, Maxim Zalalutdinov, Cory D Cress, Jeremy T Robinson The controlled dewetting and recrystallization of metal films with two-dimensional (2D) crystal over-layers enables the formation of highly textured metallic films, together with a network of metallic pores and suspended 2D crystal membranes. Mechanically-exfoliated and chemical-vapor deposited (CVD-grown) 2D crystals (e.g., graphene, h-BN, and transition-metal dichalcogenides (TMDs)) were transferred on top of metallic thin films on SiO2/Si substrates to modify the dewetting and recrystallization dynamics. After heat treatment, metal films capped with 2D crystals become textured and form pores that can span up to 60% of the planar surface area, depending on annealing conditions and 2D crystal quality. The network of suspended membranes was found to have significantly different optical and electronic properties than the supported regions. For example, enhancement in photoluminescence of nearly three orders of magnitude and spatial surface potential variations up to 300 mV. The process capabilities are exemplified through a series of heterostructures of different metal/2D crystal materials where the resulting properties highlight the influence of the networked topography. |
Tuesday, March 5, 2019 8:36AM - 8:48AM |
E13.00004: ABSTRACT WITHDRAWN
|
Tuesday, March 5, 2019 8:48AM - 9:00AM |
E13.00005: Electron Microscopy and Optical Spectroscopy of MoS2 Nanoribbons from Catalyst-Free Vapor Phase Synthesis Todd Brintlinger, Tomojit Chowdhury, Benjamin O Stephens, Thomas J Kempa We characterize MoS2 nanoribbons grown using a catalyst-free vapor phase synthesis that relies on pre-treatment of a bare Si surface. This growth method leads to the spontaneous formation of long ‘nanoribbons,’ with typical diameters of 100 nm and lengths greater than 10 µm. Despite their high aspect ratio and inherent flexibility, the nanoribbons are robust upon handling and are self-supporting, rendering them stable during transfer to support structures to allow electron microscopy. We use scanning electron microscopy to characterize the ribbon morphology and aberration-corrected scanning transmission electron microscopy to identify the phase, composition, and atomic structure of the samples. We identify that the MoS2 nanoribbons (1) are predominantly 2H-phase, (2) display a ‘sawtooth’ edge structure with corrugations on the order of 2–5 nm, (3) fold to give very low radii of curvature, and (4) contain occasional nanometer-scale triangular inclusions. Intriguingly, these high aspect ratio nanoribbons exhibit a PL peak that is blue-shifted significantly relative to that of as-synthesized and transferred 2-dimensional MoS2 sheets. |
Tuesday, March 5, 2019 9:00AM - 9:12AM |
E13.00006: Strong interlayer coupling and layer-dependent bandgap in 2D layered PdSe2 synthesized by chemical vapor deposition Li-Syuan Lu, Hui-Yu Cheng, Guan-Hao Chen, Chia-Hao Chen, Tzu-Hung Chuang, Der-Hsin Wei, Ming-Yang Li, Chih-Piao Chuu, Lain-Jong Li, Wen-Hao Chang Two-dimensional (2D) noble metal dichalcogenides, such as PtS2 or PdSe2, have attracted much attention due to their remarkable layer-dependent electronic structures and superior electrical properties for device applications. However, most of the demonstrated experiments thus far are based on mechanical exfoliations from bulk crystals. Here, we demonstrate that highly crystalline and air stable PdSe2, from bilayer up to few layers, can be synthesized by chemical vapor deposition. The atomic ratio and the lattice structure of PdSe2 have been confirmed by x-ray photoemission and polarization-resolved Raman spectra. Low-frequency Raman measurements of breathing vibration modes reveal the strong interlayer coupling, which can also be used for identifying the layer numbers [1]. Based on absorption measurements, we observed a strongly layer-dependent bandgap, which shows a gap shrinkage up to 0.5 eV with the increasing layer number from bilayer to 7 layers. The dramatically layer-dependent bandgap shrinkage is also consistent with the calculated energy gap based on density functional theory.[2] |
Tuesday, March 5, 2019 9:12AM - 9:24AM |
E13.00007: Synthetic Metal-Semiconductor Junctions of Transition Metal Disulfides Wei Sun Leong, Qingqing Ji, Nannan Mao, Yimo Han, Haozhe Wang, Aaron J Goodman, Cong Su, Yunfan Guo, Pin-Chun Shen, Zhenfei Gao, David Anthony Muller, William A Tisdale, Jing Kong Transition metal dichalcogenides (TMDs), a group of 2D materials with diverse electronic properties, are ideal candidates to build atomically thin electronics. Although critical components of an electronic device based on TMDs, such as insulator-semiconductor and semiconductor-semiconductor junctions, have been demonstrated, there is limited experimental realization of TMD-based metal-semiconductor junctions to date. Here, we report a two-step chemical vapor deposition (CVD) strategy that enables the synthesis of high-quality solely TMD-made metal-semiconductor lateral junctions. Remarkably, we discover a novel growth behavior in such lateral TMD heterojunctions: MoS2 was found to nucleate from the vertexes of multilayered VS2 flakes and evolve into monolayer polycrystals, rather than the edge epitaxy observed in other TMD lateral junctions. Furthermore, we demonstrate that lattice coherency across the lateral junction is not a necessity for low-resistance contacts, as our VS2-MoS2 junctions manifest contact resistance as low as 500 Ωµm and a Schottky barrier height as small as 30 meV, both among the best values reported to date for contacts to 2D TMDs. This work opens up a new avenue for all-2D-based synthetic electronics. |
Tuesday, March 5, 2019 9:24AM - 9:36AM |
E13.00008: Scaling a van der Waals quantum Hall semiconductor Kai Yuan, Ruoyu Yin, Xiaosong Wu, Yu Ye, Lun Dai Indium selenide (InSe), a two-dimensional (2D) layered semiconductor material, have attracted much attention recently due to their high mobility and fascinating physical properties. Nevertheless, the preparation of few-layer InSe is limited to mechanical exfoliation which hinders their potential in the future applications. Recently reports of few-layer InSe synthesized via chemical vapor deposition (CVD) method failed to maintain high mobility characteristics of InSe. Here, we explored the controlled one-step synthesis of 2D InSe nanoflakes with chemical vapor transport (CVT) by appropriately slowing down the growth rate. Diverse growth routes were developed by using different transport agents. As-grown InSe nanoflakes with thickness down to monolayer was successfully obtained. Atomic-resolution ADF-STEM imaging revealed the high quality of the as-synthesized InSe nanoflakes. Encapsulated by BN at both sizes, the electrical transport of our InSe nanoflakes shows excellent performance with carrier mobilities larger than 1000 cm2V-1s-1 at room temperature and 5000 cm2V-1s-1 at 1.5 K, enabling us further observe the quantum Hall effect. This is the first time that a quantum Hall effect was observed in as-grown 2D semiconductor materials. |
Tuesday, March 5, 2019 9:36AM - 9:48AM |
E13.00009: Theoretical insight into the mechanism for spontaneous vertical growth in ReS2 Anthony Yoshimura, Debjit Ghoshal, Tushar Gupta, Andrew House, Swastik Basu, Yanwen Chen, Tianmeng Wang, Yang Yang, Wenjia Shou, Jordan A. Hachtel, Juan Carlos Idrobo, Toh-Ming Lu, Sagnik Basuray, Vincent Meunier, Sufei Shi, Nikhil Koratkar While vertical growth can be observed in some transition metal dichalcogenides (TMDs) under special conditions, vertical growth of rhenium disulfide (ReS2) is unique in that it is thermodynamically favorable over horizontal growth regardless of substrate. In this study, we use density functional theory (DFT) to shed light on the mechanism that initiates vertical growth in ReS2 to explain its substrate-independence. We propose that ReS2 growth has two stages. First, ReS2 grows parallel to the substrate, in a manner similar to that of conventional TMDs. However, as a growing ReS2 flake reaches a critical diameter, spontaneous vertical growth is nucleated at points near the flake’s center. At these sites, an additional Re atom binds to a cluster of “pinched” Re atoms, leaving an under-coordinated S atom protruding out of the ReS2 plane. This S atom is “reactive” and readily binds to free Re and S atoms, initiating growth in a direction perpendicular to the ReS2 surface. The resulting vertical ReS2 arrays possess high surface-to-volume ratios and can therefore accommodate a broad range of applications including surface enhanced Raman spectroscopy, field emission, and solar-based disinfection of bacteria. |
Tuesday, March 5, 2019 9:48AM - 10:00AM |
E13.00010: Stoichiometric Control of Structural Phases in Two-Dimensional NbS2 Nanoflakes Amanda Coughlin, Wencao Yang, Zhen Li, Shixiong Zhang Two-dimensional transition metal dichalcogenides (TMDs) are known to exist in multiple structural phases (1T, 2H, and 3R etc.) each with distinct physical properties. The ability to tune the crystal structures in a controlled manner provides an effective route to engineer the respective properties and is therefore of significant technological importance. In this study, we use NbS2 nanoflakes as an example to demonstrate the control of structural phases in layered TMDs by tuning their stoichiometry. The as-grown NbS2 has a rhombohedral 3R phase which can be readily transformed into another structure via a simple annealing process. By varying the annealing conditions, we realize several different structural phases as identified by Raman spectroscopy. The reversibility and the underlying mechanism of phase transformations are also studied. |
Tuesday, March 5, 2019 10:00AM - 10:12AM |
E13.00011: Spectroscopic Characterization of Colloidally Synthesized, Anisotropic 2D SnS Adam Biacchi, Brian Alberding, Son T. Le, Sugata Chowdhury, Joseph Hagmann, Sujitra Pookpanratana, Curt A Richter, Edwin Heilweil, Angela Hight Walker Solution routes afford scalable means of manufacturing size-, shape-, and composition-controlled nanoscale electronic materials. We have developed solution routes to monodisperse 2D semiconductor SnS nanostructures, an easily processable and cost-efficient alternative to exfoliation and gas-phase deposition techniques. These colloidal chemistries afford two distinct SnS morphologies: nanoribbons and square nanosheets. The uniformity and morphology of the nanocrystals were verified using TEM, SEM, AFM, and optical microscopy. A spectroscopic investigation of the inherent structural and electronic properties of nanocrystals showed the α-SnS polymorph adopts a layered orthorhombic crystal structure, isostructural with black phosphorus. These 2D crystals are anisotropic, with in-plane atoms adopting the armchair configuration along one axis and zigzag in the orthogonal direction. Detailed polarization-, wavelength- and temperature-dependent Raman spectroscopy provide key insight into the crystallographic details and low-frequency phonon behavior. Back-gated devices fabricated from individual crystals reveal electronic transport information and four-point probe methods show the anisotropic conductivity resulting from a black phosphorus-like bonding arrangement found in 2D SnS. |
Tuesday, March 5, 2019 10:12AM - 10:24AM |
E13.00012: Engineering Defect Transition-Levels through van der Waals Heterostructure Akash Singh, Aaditya Manjanath, Abhishek Kumar Singh Tuning the defect transition levels in 2D semiconductors without significantly altering the integrity of the materials remains one of the most difficult challenges. Among the 2D materials, monolayer MoS2 is considered as a front-runner for device applications, does not have a single intrinsic shallow defect, thereby limiting its applications. We demonstrate that the deep defect levels created by a cation vacancy in a monolayer of MoS2, can be tuned to a shallow level by forming the van-der-Waals heterostructure of it with a monolayer of WS2, while maintaining their structural and compositional integrity intact. In result, the deep defect levels are shallowed by nearly 4(V-1Mo) and 2(V-1W) times, respectively, compared to their monolayer counterparts. The overall change in dielectric constant rescales the defect transition levels in a heterostructure. Our finding has the potential to revolutionize the doping strategy of the 2D materials and could pave the way for 2D electronics. |
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