Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session F13: 2D Materials (General) -- Scaled GrowthFocus
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Sponsoring Units: DMP DCOMP Chair: Joshua Robinson, Pennsylvania State University Room: BCEC 153B |
Tuesday, March 5, 2019 11:15AM - 11:27AM |
F13.00001: Single-Step Direct Growth of Large-Area Graphene and Graphene-Based Nanostructures on Silicon by Plasma-Enhanced Chemical Vapor Deposition (PECVD) Wei-Shiuan Tseng, Yen-Chun Chen, Chen-Chih Hsu, Nai-Chang Yeh Chemical vapor deposition (CVD) of graphene on metallic substrates (e.g., Cu, Ni) at high temperatures (~ 1000 C) has been the most common process for large-scale synthesis of graphene. However, high-temperature growth processes are incompatible with CMOS technology. Moreover, the synthesis of graphene on metallic substrates requires additional sample transfer processes to semiconductor substrates, which often result in degradation of the sample quality. Therefore, it is highly desirable to explore direct growth of graphene on silicon for better integration of graphene into current semiconductor industry. In this study, we demonstrate the feasibility of a single-step method for direct growth of large-area graphene and graphene-based nanomaterials on silicon by means of PECVD without active heating. By proper control of the PECVD growth parameters, we can obtain a variety of graphene-based materials, including large-area graphene flakes, graphene sheets, and vertically grown graphene nanostripes. Correlation between the growth recipes and the resulting sample characteristics is made by studying the Raman spectroscopy, XPS, UPS, SEM and AFM, which helps unveil the growth mechanism and optimize the growth quality of graphene on silicon. |
Tuesday, March 5, 2019 11:27AM - 11:39AM |
F13.00002: Synthesis and characterization of large-area single-crystal sheets of borophene on Cu(111) surface Rongting Wu, Ilya K. Drozdov, Stephen Eltinge, Percy Zahl, Sohrab Ismail-Beigi, Ivan Bozovic, Adrian Gozar Borophene, a theoretically proposed two-dimensional boron allotrope, has attracted attention as a candidate material platform for high-speed and flexible electronics. However, the single-crystal domains produced so far are too small for device fabrication. We report on synthesis of borophene on Cu(111) monitored in situ by low-energy electron microscopy (LEEM), diffraction and scanning tunneling microscopy, and ex-situ by X-ray photoelectron spectroscopy and atomic force microscopy. By growing borophene on Cu(111) surfaces, we obtain large single-crystal domains, up to 100 μm2. We show that the crystal structure is a novel triangular network with h = 1/5 concentration of hexagonal vacancies. LEEM imaging capabilities provide detailed information about borophene growth, island faceting, evaporation and sub-surface dissolution. Data and calculations indicate charge-transfer coupling to substrate without significant covalent bonding. Our work sets the stage for fabricating borophene-based devices and substantiates the idea of borophene as a model for artificial 2D materials development. |
Tuesday, March 5, 2019 11:39AM - 11:51AM |
F13.00003: Direct graphene growth on Anodic Aluminum Oxide (AAO) under different conditions using chemical vapor deposition Aamna AlShehhi, Irfan Saadat, Faisal AlMarzooqi, Amal Al Ghaferi, Khadija Al Daghar Graphene is one of the promising 2D material due to their remarkable electrical, mechanical and chemical properties. In general growth conditions can be manipulated to synthesis graphene with different layer composition and properties. Direct synthesis of graphene is critical to establish new applications and come up with a manufacturing process for current applications. Recent studies started to focus on direct graphene growth on AAO and potential usage in new applications. The novelty of my study focusing on distinguishing between the quality of graphene growth with low pressure and ambient pressure.This paper will show the results of direct CVD graphene growth on AAO films with pore size ranging from 200 - 40(nm) under different conditions such as pressures (ambient & vacuum) and flow rates. (nm) .These parameters play a critical role in the quality and various properties of graphene growth. The presence of graphene was confirmed via Raman spectroscopy with a laser wavelength of 532 nm. The D-mode, G-mode and 2-D mode appears at approximately 1348 cm-1,1616 cm-1 and 2690 cm-1 respectively. |
Tuesday, March 5, 2019 11:51AM - 12:27PM |
F13.00004: Wafer-scale Growth and Assembly of 2D Semiconductors Invited Speaker: Kibum Kang High-performance semiconducting films with precisely engineered thicknesses and compositions are essential for developing next generation electronic devices, which are becoming more integrated, complex, and multifunctional. My talk will introduce the novel processes that enable atomic-scale control of the thickness and spatial composition of semiconducting films on the wafer-scale. These processes include: (i) the wafer-scale generation of monolayer van der Waals semiconductors such as transition metal dichalcogenides (TMDCs) via metal-organic chemical vapor deposition (MOCVD), (ii) the atomic-level engineering of vertical thickness and composition through the layer-by-layer assembly of TMDC monolayers, and (iii) the transfer of atomically engineered films, using their van der Waals nature, onto arbitrary substrates. These capabilities provide a new material platform for both fundamental research and practical applications, including incorporation into existing integrated circuit technology to form hybrid materials (i.e. TMDC/CMOS) and boost electrical and optical functionality. |
Tuesday, March 5, 2019 12:27PM - 12:39PM |
F13.00005: Direct growth of mm-size twisted bilayer graphene (tBLG) by plasma enhanced chemical vapor deposition (PECVD) Yen-Chun Chen, Wei-Hsiang Lin, Wei-Shiuan Tseng, Chien-Chang Chen, George R Rossman, Yu-Shu Wu, ChiiDong Chen, Nai-Chang Yeh PECVD techniques have been shown to be an efficient method to achieve single-step synthesis of high-quality monolayer graphene without the need of active heating. Here we report our progress in PECVD-growth of single-crystal hexagonal bilayer graphene (BLG) flakes and mm-size BLG films, both with the interlayer twisted angle controlled by the PECVD growth parameters. The twisted angle between stacked bilayer is determined by a combination of three experimental approaches, which include: 1) directly measuring the orientation of edges between two stacked layers by scanning electron microscopy, 2) evaluating the twisted angle-dependent Raman spectral characteristics of the G-, 2D- and R¢-modes of graphene, and 3) analyzing the Moiré period captured by scanning tunneling microscopy. We find that the average twisted angle of BLG samples can be controlled from 0°(for perfect AB stacking) to ~ 20°, and the spread of twisted-angles for a given growth condition can be reduced to less than 7° over mm-size tBLG films. More comprehensive studies of various properties of PECVD grown-tBLG will be reported in this talk. |
Tuesday, March 5, 2019 12:39PM - 12:51PM |
F13.00006: Synthesis of Artificial 2D Lattices of Monolayer Multi-junctions Yi-Cheng Chiang, Chun-An Chen, Kuan-Chang Chiu, Kuan-Hua Huang, Ying-Yu Lai, Xin-Quan Zhang, Erh-chen Lin, Meng-Hsi Chuang, Jenn-Ming Wu, Yi-Hsien Lee Recently, monolayers of transition metal dichalcogenides (TMDs) are ideal building blocks for constructing artificial 2D lattices. Heterostructures with multi-junctions of more than two monolayer TMDs are intriguing for exploring new physics. Here, the laterally stitched TMDs and the vertically stacked monolayers are constructed. A low growth temperature synthesis and a clean transfer method are developed for high quality hetero-interfaces. With optimized parameters, atomically sharp interfaces are successfully achieved in the synthesis of in-plane artificial lattices of the WS2/WSe2/MoS2. Characterizations of the hetero-interfaces are presented. |
Tuesday, March 5, 2019 12:51PM - 1:03PM |
F13.00007: Boron and Nitrogen co-doping of Graphene by CVD Tomotaroh Granzier-Nakajima, Lavish Pabbi, Mauricio Terrones, Eric Hudson Substitutional doping of graphene offers a chance to modify its properties for various applications. Here using low pressure chemical vapor deposition we grow graphene doped simultaneously by both boron and nitrogen. Theoritcal calculations have shown that in such systems boron and nitrogen dopants tend to segregate and form hexagonal boron-nitride like islands within the graphene sheet.1,2 Using STM we are able to observe these dopant structures with atomic resolution and show the results here. |
Tuesday, March 5, 2019 1:03PM - 1:15PM |
F13.00008: The Growth and Characterization of PECVD Silicene Battogtokh Jugdersuren, Xiao Liu, James Clifford Culbertson, Nadeem Mahadik Silicene, a two-dimensional nanoscale allotrope of silicon atoms with a buckled honeycomb structure, is predicted to have a many interesting features. There is no evidence for the existence of natural silicene. Until recently, molecular-beam epitaxy (MBE) has been the only successful technique for silicene synthesis. Recently, we have found that plasma-enhanced chemical-vapor deposition (PECVD) has the potential to grow economically viable, large scale, high-quality mono- and multi-layer silicene comparable to that grown using MBE. In addition, we have shown that PECVD grown silicene is naturally hydrogenated and resistance to oxidation. In this work, we have grown PECVD silicene on polycrystalline and single crystalline silver thin films and characterized them using Raman spectroscopy, X-ray diffraction, and X-ray photo-electron spectroscopy. The results show that we can grow nearly defect-free silicene on single crystalline Ag(111) films. We will discuss crystalline structure, hydrogenation, and oxidation-resistance properties of the PECVD silicene. |
Tuesday, March 5, 2019 1:15PM - 1:27PM |
F13.00009: Growth Physics of MoS2 Layer on the MoS2 Surface: A Monte Carlo Approach Kamalika Ghatak, Dibakar Datta, Jatin Kashyap Layered Transition Metal Dichalcogenides (TMDs) are getting attention due to their layer-dependent tunable optoelectronic and mechanical behavior and the control over the experimental growth technique is required to synthesize deserved stacked products. Alongside, a probabilistic computational approach is necessary to gain deeper insight into the in-situ growth physics. We, therefore, performed Grand Canonical Monte Carlo (GCMC) simulation as implemented in LAMMPS package with ReaxFF potential, and developed our in-house Kinetic Monte Carlo (KMC) code to model the growth physics of MoS2 layer on the substrate. We considered various pristine and defective growth surface to track the movement of the individual Mo and S. Non-periodic surface with various edge termination (such as chalcogen and metal termination) was also explored. Our Monte Carlo study captures the formation of the MoS2 on the perfect MoS2 surface starting with the individual Mo and S flux. We find that the growth temperature plays a crucial role in governing growth mechanisms. Further investigation is on-going on the growth physics of MoS2 and other TMDs (e.g., WS2) on pristine and defective substrates. Our modeling approach provides guidelines for the experimentalists for the optimal design of TMD bilayer growth. |
Tuesday, March 5, 2019 1:27PM - 1:39PM |
F13.00010: Cooling-mediated One-step Synthesis of Monolayer WSe2/WSe2xTe2-2x Lateral Heterostructures for High-Performance Spectral Photodetectors Sangmin Kang, Chia-Hao Lee, Yifei Li, Zijing Zhao, Kai Xu, Shushan Xia, Hojoon Ryu, Pinshane Huang, Wenjuan Zhu Tellurium (Te) based transition metal dichalcogenides (TMDCs), especially tungsten ditelluride (WTe2), have attracted intensively owing to their unique electrical and optical properties. However, the ternary alloy tungsten selenium telluride (WSe2xTe2-2x) and its lateral hetero-structure with other TMDCs remains largely unexplored due to the considerable challenge in synthesizing these materials, since WTe2 has very weak bonding and tends to decompose at high reaction temperature. Here, we demonstrate a successful one-step synthesis of monolayer WSe2/WSe2xTe2-2x lateral hetero-structures via cooling-mediated chemical vapor deposition. We find that the cooling rate and flow ratio between argon and hydrogen gas are crucial factors for the morphology. The Te incorporation in the alloy is studied by aberration-corrected scanning transmission electron microscopy. The correlation between Te composition and the bandgap of the alloy is simulated by density functional theory. Furthermore, through the study of the optical and electrical properties, we demonstrate the possibility of high-performance spectral photodetectors with spatially graded bandgap. |
Tuesday, March 5, 2019 1:39PM - 1:51PM |
F13.00011: WITHDRAWN ABSTRACT
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Tuesday, March 5, 2019 1:51PM - 2:03PM |
F13.00012: Synthesis of High Quality Monolayer Transition Metal Dichalcogenides using Direct Liquid Injection Kathleen McCreary, Enrique Cobas, Aubrey Hanbicki, Berend Jonker In recent years, interest in monolayer transition metal dichalcogenides (TMDs) has rapidly increased, spurred by the possibility for integration into a variety of technologies such as photodetection, flexible electronics, and chemical sensing. While fundamental investigations can be performed on exfoliated flakes or chemical vapor deposition synthesized isolated islands, the limited size resulting from these techniques poses a significant barrier for implementation of TMDs in technological applications. To overcome these obstacles, new synthesis avenues should be explored. Here, we outline a novel technique that utilizes a commercially available Anneal Sys growth chamber equipped with direct liquid injection (DLI) heads for all precursors. The use of liquid, rather than solid precursors, provides fine control of both metal and chalcogen precursors leading to the synthesis of monolayer MoS2 across cm2 areas. Photoluminescence, Raman and XPS are used to evaluate DLI grown MoS2, and indicate high quality material, with metrics comparable to or better than exfoliated and chemical vapor deposition grown MoS2. |
Tuesday, March 5, 2019 2:03PM - 2:15PM |
F13.00013: Controlled CVD growth of MoTe2 and their use in near-infrared light detection Zhengtang Luo, Jiawen You Due to their low symmetry ultrathin structures and unconventional dielectric screening effects, 2D transition metal dichalcogenides (TMDs) have attracted significant research attention utilizing their tunable optical-electronic properties. We established general strategies for to synthesize high-quality graphene and TMDs layers with tailored properties using chemical vapor deposition (CVD). Here, we demonstrate a salt-induced CVD strategy to synthesize mono- and few-layer 1T’ and 2H phase MoTe2, exploiting richer electronic properties of this materials derived from their tunable structures. The obtained materials has demonstrate exceptional performance when used for the near-infrared (NIR) light detection, arise from their reduced band gap of 2H phase MoTe2. This study provides a new materials synthesis method aiming for the fabrication of for highly efficient, and broadband NIR photodetector. |
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