Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session L55: Devices from 2D Materials -- Optical SpectroscopyFocus
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Sponsoring Units: DMP Chair: Nick Vamivakas, University of Rochester Room: BCEC 254B |
Wednesday, March 6, 2019 11:15AM - 11:27AM |
L55.00001: Wavelength Estimation of Light Source via Machine Learning Techniques using Low Cost 2D Layered Nano-material Filters Davoud Hejazi, Sarah OstadAbbas, Swastik Kar We created a vector of low-cost filters for estimating the wavelength of a light source in the range of 300nm-1100nm using gradually differing mixtures of nano-flakes of semiconducting materials, Molybdenum-Disulfide (MoS2) and Tungsten-Disulfide (WS2). The nano-flakes were produced by method of Liquid-Phase Exfoliation and Sonication. We studied the incident and transmitted intensities of light passing through these filters and derived a statistical model for the behavior pattern of the filters for incident light. By employing machine learning techniques we estimated the wavelength distribution of incident light with accuracy of ≤ %1 using the incident and transmitted sensor readings for intensity of light. |
Wednesday, March 6, 2019 11:27AM - 11:39AM |
L55.00002: Interface-Driven Nonlinear Optical Response at MoS2/Ferroelectric Composite Structures Dawei Li, Xi Huang, Zhiyong Xiao, Hanying Chen, Le Zhang, Ding-Fu Shao, Evgeny Y Tsymbal, Yongfeng Lu, Xia Hong Integrating layered van der Waals materials such as the transition metal dichalcogenides with ferroelectrics offers the opportunity to introduce new functionalities to the 2D platform, including nonvolatile memory and programmable junctions. In this work, we report a novel nonlinear optical response emerged at the interface between monolayer MoS2 and ferroelectric thin films. We have pre-patterned ferroelectric domain structures with polarization up and down domains on epitaxial PbZr0.2Ti0.8O3 (PZT) thin films using piezoresponse force microscopy, and then transferred on the top MoS2 flakes. We then carried out second-harmonic generation (SHG) microscopy studies on the composite structures. In the reflection mode, we find that the SHG intensity on the ferroelectric domain wall (DW) is highly modulated compared with those on both polar domains, either significantly enhanced or suppressed depending on the chirality of the DW. Stacking angle dependence demonstrates that MoS2 also tunes the polarity of the SHG response on the DW. Our study points to a new strategy to achieve tailored light polarity and intensity modulation via nanoscale ferroelectric control. |
Wednesday, March 6, 2019 11:39AM - 11:51AM |
L55.00003: Investigation of Intrinsic Optical Characteristics in MoS2 Phototransistors using Van der Waals Heterostructure Jinsu Pak, Ilmin Lee, Kyungjune Cho, Wang-Taek Hwang, Jae-Keun Kim, Keehoon Kang, Woo Jong Yu, Seungjun Chung, Takhee Lee Since the photodetectors based on molybdenum disulfide (MoS2) emerged, diverse researches have been conducted to obtain high performance as the photodetectors.[1] However, it is not trivial to study the intrinsic optical properties of MoS2 because of the reflected incident light by the generally used opaque substrate such as SiO2. Here, we report our study of the intrinsic optical characteristics in MoS2 phototransistor through the transparent device structure fabricated by 2D materials-based heterostructure. The internal photo-responses (corresponding to the photo-response generated by absorbed photons in a MoS2 sheet) such as responsivity, detectivity, and quantum efficiency were carefully investigated. The measured results indicated that the internal quantum efficiency was not strongly dependent on the wavelength of the incident light, whereas the external quantum efficiency was. Our study helps to understand the intrinsic optical characteristics of 2D-based photodetectors, and will provide an insight for the realization of 2D-based transparent photodetectors.R |
Wednesday, March 6, 2019 11:51AM - 12:03PM |
L55.00004: Nonlinear Plasmonics with 2D Excitons Bekele Badada, Matthew Klein, Rolf Binder, Adam Alfrey, Max McKie, Michael Koehler, David Mandrus, Takashi Taniguchi, Kenji Watanabe, Brian LeRoy, John Schaibley We investigate the interactions between propagating surface plasmon polaritons (SPP) in a metallic waveguide and excitons in WSe2 monolayer. The WSe2 monolayer was encapsulated by few layer thick hBN and transferred onto a lithographically defined gold waveguide using dry transfer technique. SPPs were launched by focusing a tunable laser onto an integrated input grating coupler and scattered out using another grating coupler. Both linear and nonlinear response of SPP-exciton interactions were measured. We report a very large linear absorption of SPP ~ 73% when the SPP is tuned to the exciton energy. For the nonlinear response, we report both optical-pumped and SPP-pumped differential SPP transmission measurements. For the SPP-pumped case, we report a large differential transmission (DT/T) over 4%. These results are highly consistent with a theoretical model of the linear and nonlinear SPP-exciton response. In our model, the SPP-exciton wave is based on an eigenmode analysis in the linear response regime, which is then perturbatively extended to the nonlinear regime. We believe that our device architecture and analysis could pave the road towards all-plasmonic modulators, amplifiers and transistors. |
Wednesday, March 6, 2019 12:03PM - 12:15PM |
L55.00005: Low-frequency Raman signature of Ag-intercalated MoS2: A first-principles study. Natalya Sheremetyeva, Drake Niedzielski, Damien Tristant, Lauren E. Kerstetter, Ama Agyapong, Anna C. Domask, Suzanne Mohney, Vincent Meunier Two-dimensional layered materials (2DMs) are promising candidates for novel electronic devices as their electronic properties can be tuned e.g. by controlling their layer number. Precise characterization of 2DMs' is crucial for exact property control. Raman spectroscopy is a nondestructive technique that can identify even small structural/electronic changes. |
Wednesday, March 6, 2019 12:15PM - 12:27PM |
L55.00006: Tailoring the electroluminescence of dual-gated monolayer p–n diodes Erik Lenferink, Kenji Watanabe, Takashi Taniguchi, Nathaniel Stern Owing to their direct bandgaps and atomic-scale thickness, monolayer transition metal dichalcogenides have been heavily investigated for optoelectronic applications. Their potential for atomically-thin visible frequency light sources can be realized by lateral monolayer p–n diodes defined by local electrostatic gates. Control over the spectral distribution and polarization of the electroluminescence is desirable for integrating these prototypical monolayer LEDs into optoelectronic and nanophotonic devices with tunable coupling. The high electric fields near the p–n interface in these single-monolayer devices provide a route for in situ control of emission. Here, we discuss electrical tuning of the electroluminescence from the electrostatically-induced interface of gate-defined monolayer WSe2 p–n diodes. We observe strong linear polarization (∼ 50%) of the electrically-pumped luminescence and a gate-tunable emission energy shift originating at this interface. Current-induced valley polarization, a possible avenue to achieving electrically-controlled circularly polarized emission, is also investigated with spatially-resolved Kerr rotation at cryogenic temperatures |
Wednesday, March 6, 2019 12:27PM - 12:39PM |
L55.00007: Characterizing the low doping regime and charge fluctuation in graphene using Raman spectroscopy. Zhuofa Chen, Nathan Jean Carl Ullberg, David Barton, Anna K Swan Graphene without charge impurities is essential for high-quality transport-based devices. Here we propose using Raman spectroscopy, as opposed to labor-intensive transport measurements, to monitor low-level accidental doping and charge fluctuation in graphene. At low doping level, monitoring the 2D band splitting reveals a whole host of information on charge density screening in graphene [1]. This method provides orders of magnitude higher precision than the reported results using the G-band shift. Our work provides a simple, noninvasive way to explore doping levels and charge fluctuation in graphene, which is important to evaluate the quality of graphene before fabricating graphene-based devices. |
Wednesday, March 6, 2019 12:39PM - 12:51PM |
L55.00008: Low-Temperature Interfacial States of MoS2-Pentacene Heterojunctions Teodor Stanev, Trevor LaMountain, Vinod Sangwan, Hadallia Bergeron, Mark Hersam, Nathaniel Stern Layered 2D materials such as transition metal dichalcogenides are fundamental components for building more complex heterostructures using organic molecules, nanostructures, or other layered materials. Organic thin film solids of pentacene, a well understood polycyclic aromatic hydrocarbon used commonly for photovoltaics and thin-film FETs, has been used to form mixed dimensional p-n heterojunctions with 2D MoS2, wherein the type II band alignment leads to ultrafast hole transfer across the junction. Here, we report low temperature optical spectroscopy showing distinct optical features that emerge in the pentacene-MoS2 heterostructure. We observe the quenching of pentacene singlet/triplet-emission and of MoS2 defect photoluminescence as well as the emergence of a narrow emission feature at low temperatures. The power dependence and lack of response to local back-gating suggest these effects are not from charge doping or bound excitons. These results demonstrate the diverse control over opto-electronic properties obtainable by combining low-dimensional materials. |
Wednesday, March 6, 2019 12:51PM - 1:03PM |
L55.00009: ABSTRACT WITHDRAWN
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Wednesday, March 6, 2019 1:03PM - 1:15PM |
L55.00010: Rapid and High Sensitivity Imaging of Two-dimensional Materials by Stimulated Raman Scattering Microscopy Jiwei Ling, Xianchong Miao, Minbiao Ji
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Wednesday, March 6, 2019 1:15PM - 1:27PM |
L55.00011: Electrostatic control of exciton flux in van der Waals heterostructures Dmitrii Unuchek, Alberto Ciarrocchi, Ahmet Avsar, Kenji Watanabe, Takashi Taniguchi, Andras Kis Large exciton binding energy in recently discovered two-dimensional semiconductors makes exciton physics accessible even at room temperature in these materials. Particular interest has been given to the interlayer excitons in van der Waals heterostructures based on transition metal dichalcogenides (TMDCs) with type-II band alignment. Whereas individual two-dimensional materials have short exciton diffusion lengths, the spatial separation of electrons and holes in different layers in heterostructures increases exciton lifetime and thus helps to overcome this limitation. In addition, this charge separation realizes built-in out-of-plane electric dipole moment, allowing exciton manipulation via an external electric field, showing promise for next-generation photonic devices relying on excitonic effects. Here, we present van der Waals devices made of TMDCs heterostructures encapsulated in h-BN with graphene control gates, which allow us to manipulate exciton dynamics by creating electrically reconfigurable potential profiles for the exciton flux. Our excitonic device demonstrates electrically controlled transistor actions at room temperature, that holds great promise for realizing small and efficient interconnects between optical data transmission and electrical processing systems. |
Wednesday, March 6, 2019 1:27PM - 1:39PM |
L55.00012: Directional coupling of valley exciton emissions from monolayer MoS2 on periodic plasmonic nanostructures Chien-Ju Lee, Chih-Lun Wu, Li-Shuan Lu, Wen-Hao Chang The unique coupled spin-valley physics in two-dimensional (2D) transition metal dichalcogenides (TMDs) has triggered abundant research activities in realizing valleytronic applications. Due to the valley contrast optical selection rule, excitons in monolayer TMDs formed at two degenerate but inequivalent K and K’valleys can couple to light with different helicities. Here, we demonstrate the spatial separation of valley-polarized excitons at room temperature by coupling monolayer MoS2 with the surface plasmon polariton (SPP) of a periodic metallic structures. Due to the spin-orbit coupling of light, the SPP waves excited by exciton emissions with opposite helicities interacting with the periodic metallic struuctures can be separated into different directions. When the exciton emissions are on resonance with the SPP modes, we observe the valley-dependent directional coupling of exciton emissions in both real and momentum space by polarization-resolved photoluminescence imaging. Our results demonstrate a route for controlling and detecting the valley polarization of TMDs by optical means. |
Wednesday, March 6, 2019 1:39PM - 1:51PM |
L55.00013: Generating Strain in 2D Materials using Microelectromechanical Systems Mounika Vutukuru, Jason W Christopher, Zhuofa Chen, David John Bishop, Anna K Swan 2D materials are unique in that many of their material properties, such as doping and band-gap, are dynamically tunable. Strain engineering is a promising way to access and tune their electronic properties. We integrate 2D materials with MEMS technology which offers tremendous control over the strain field and is readily compatible with modern electronics. We have previously achieved success in straining MoS2 to 1.3% using MEMS [1]. Here we report on the use of electrothermal MEMS actuators to uniaxially strain monolayer graphene, as confirmed through micro-Raman spectroscopy. This was achieved through the development of gold micro-riveting to anchor the 2D material in place. We also examine two terminal electrical transport through MEMS-strained graphene. The application of controlled strain using MEMS therefore allows for the investigation of electrical and mechanical interplay in strained 2D materials, opening the door to the development of strain-based 2D electronics. |
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