Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session D57: 2D Emerging DevicesFocus
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Sponsoring Units: APS Chair: MARIO LANZA, Soochow University Room: Mile High Ballroom 3A |
Monday, March 2, 2020 2:30PM - 2:42PM |
D57.00001: Ultra-high sensitive gas sensor based on graphene/carbon nanotube barristor Younggyu You, Do-Hyun Park, Jun-Ho Lee, Inchul Choi, Sung-Il Jo, Goo-Hwan Jeong, Eleanor Campbell, Hyun-Jong Chung, Jhang Sung Ho We have investigated switching characteristics in graphene/semiconducting single-walled carbon nanotube (SWCNT) junction device, so-called graphene/SWCNT barristor. We modulated the Schottky barrier between the graphene and the carbon nanotube by using top and bottom gate electrodes, and achieved on-off ratio of 108 and the subthreshold swing of 74 mV/dec with high current density. In addition, we demonstrated the potential of our device as a NO2/NH3 gas sensor. Graphene/SWCNT barristor showed the 107 % of sensitivity for the 100 ppm NO2 gas, and 105 % of sensitivity for the 100 ppm NH3 gas. Also, our device is sensitive enough to detect NO2 gas down to 25 ppb concentration with 400 % sensitivity. |
Monday, March 2, 2020 2:42PM - 2:54PM |
D57.00002: Circular nanoelectromechanical resonators based on hexagonal boron nitride graphene heterostructures Rohit Kumar, Deric W Session, Harrison Paas, Ryuichi Tsuchikawa, Vikram V Deshpande 2D materials like graphene and h-BN, to name a few, when layered on top of each other offer a new class of metamaterials. Especially, the twisting degree of freedom between two layers has opened the window for new phenomenon not explored before. The mechanical properties of these heterostructures in the form of nanoelectromechanical systems (NEMS) have not been studied extensively. Their exceptional attributes like ultra-low mass, robustness and high tunability make 2D materials suitable for NEMS which holds promise for various technological applications viz. ultrafast sensors, actuators etc. We report fabrication and characterization of hexagonal-boron nitride (h-BN) graphene heterostructure based circular nanoelectromechanical resonators on sapphire substrates. The device is measured at cryogenic temperatures and exhibits multiple mode frequencies which are highly tunable with gate voltage. A continuum mechanics model is employed to analyze the transmission (S21) data of fundamental mode. Parameters like built-in tension obtained from the fit are used to identify the indices (m, n) of higher mechanical modes observed for the device. NEMS could offer a way to study the electronic phenomena such as superconductivity in twisted bilayer graphene heterostructures. |
Monday, March 2, 2020 2:54PM - 3:06PM |
D57.00003: Advances in MEMS based Strain Engineering of 2D Materials Mounika Vutukuru, Zhuofa Chen, Anna K Swan Strain on 2D materials is an exciting avenue to explore material properties as well as induce novel phenomena, such as strain-dependent electron-hole plasma (EHP) formation in MoS2, or pseudo-magnetic field generation in graphene. In this work, we successfully incorporate MoS2 and graphene with microelectromechanical systems (MEMS) to controllably introduce strain, while simultaneously observing 2-terminal transport and electro-optical changes. We fabricate suspended 2D material integrated MEMS devices using a novel polymer transfer microstructure without damaging the MEMS or the 2D film. By electrically powering our devices, suspended 2D materials undergo controllable, reversible uniaxial strain which we characterize by optical spectroscopy. Equipped with two-terminal contacts, we explore the conductance of suspended 2D materials while simultaneously straining the material in air, with the goal of achieving different strain gradients for accessing novel physics. |
Monday, March 2, 2020 3:06PM - 3:18PM |
D57.00004: Probing layered magnets with graphene van der Waals heterostructures Jesse Balgley, Takashi Taniguchi, Kenji Watanabe, Erik Henriksen Layered magnets are promising platforms for science and applications including novel quantum magnetic phases, nanoscale magnetic memory, and spintronics devices. However common bulk probes such as neutron and x-ray scattering or thermal probes are difficult or impossible to use to characterize these materials in the few-layer limit. We seek to develop new approaches for probing devices incorporating single-/few-layer magnets. Electronic transport in graphene can be influenced by both nearby and nonlocal scatterers. We have found that the resistance of graphene exhibits a nonmonotonic change with temperature when placed in contact with a material undergoing a magnetic phase transition. This is reminiscent of “critical resistivity” measurements in (anti-)ferromagnetic metals dating back over 50 years, which show that transport can be sensitive to spin-scattering. Motivated by these findings, we explore transport in graphene separated from layered magnets by thin hexagonal boron nitride (hBN). We find unusual nonmonotonic changes in graphene resistance persist even when the graphene is only in contact with hBN, suggesting that nearby magnetic materials impact transport. We show results for devices incorporating magnetic metals (Gd, Dy) as well as layered magnets α-RuCl3 and FePS3. |
Monday, March 2, 2020 3:18PM - 3:30PM |
D57.00005: NEGF simulations of metal contacts for graphene nanoribbon based device Hancheng Qin, Wenchang Lu, Jerry Bernholc For nanoscale electronic devices, the precise atomic structure of the metal contact plays a significant role on the performance of the device. We use an accurate, DFT-based non-equilibrium Green’s function method with variationally-optimized localized orbitals to study contacts between different metals and graphene and/or graphene nanoribbons (GNRs). For on-top metal contacts not chemically bound to graphene, we have found that Ti contacts have lower resistance than other metals, such as Au, Ca, Ir, Pt, and Sr. We will discuss channel length effects on the off-state current and the required minimum channel and metal-graphene contact lengths for applications. Other contact structures (side contacts with chemical bonds) will also be discussed. |
Monday, March 2, 2020 3:30PM - 3:42PM |
D57.00006: An ultra-high vacuum system for fabricating 2D material devices Shuaifei Guo, Satoru Masubuchi, Nai Zhou Wang, Kenji Watanabe, Takashi Taniguchi, Xianhui Chen, Tomoki Machida, Yuanbo Zhang Atomically thin two-dimensional (2D) materials exhibit a rich set of electronic properties that may impact future electronic and optoelectronic applications. Many 2D materials, however, are prone to degradation in the presence of trace amount of oxygen or water vapor. The study of the intrinsic properties of these 2D materials requires protection from degradation agents during sample fabrication process. To this end, we design and build an ultra-high vacuum (UHV) system, in which the entire sample fabrication is performed under a base pressure lower than 5×10-10 mbar. We demonstrate the functionality of this UHV fabrication system by fabricating black phosphorus heterostructures completed with electrical contacts and gate electrode for transport measurements. |
Monday, March 2, 2020 3:42PM - 4:18PM |
D57.00007: Integration of 2D materials for Device applications Invited Speaker: Lain-Jong Li Selected by Focus Topic Organizer (Deji Akinwande) |
Monday, March 2, 2020 4:18PM - 4:30PM |
D57.00008: Towards the ideal diode: Half-metal spin-gapless semiconductor junctions based on 2D materials Ersoy Sasioglu, Thorsten Aull, Stefan Bluegel, Ingrid Mertig Conventional semiconductor diodes have a junction barrier that electrons have to overcome and |
Monday, March 2, 2020 4:30PM - 4:42PM |
D57.00009: Improved broadband on-chip time domain terahertz spectrometer for van der Waals heterostructures Alex Potts, Joshua O Island, Eric Spanton, Peter Kissin, Anthony P McFadden, Liam Cohen, Chris J Palmstrom, Richard Averitt, Andrea Young Time domain THz spectroscopy is a powerful technique for studying low-energy excitations in quantum materials, but is typically restricted to samples physically larger than the electromagnetic diffraction limit (~0.3 mm). We present an on-chip THz time domain spectrometer based on transmission line-coupled photoconductive switches fabricated by aligned transfer of epitaxially grown ErAs superlattices. We benchmark our bandwidth and dynamic range, which shows significant improvement over radiation damaged silicon-based devices on silicon substrates, and anticipate the technique’s use in studying dynamics and non-equilibrium phases in exfoliable van der Waals materials and heterostructures. |
Monday, March 2, 2020 4:42PM - 5:18PM |
D57.00010: 2D Materials and Heterostructures: from Electronic Transport to Emergent Memory, Neuromorphic and Optoelectronic Applications Invited Speaker: Feng Miao Two-dimensional (2D) materials and heterostructures have emerged as promising candidates for post-Moore electronics due to their unique electronic properties and atomically thin geometry. I will start with our studies on 2D semiconductors with low lattice symmetry and type-II Weyl semimetals. In atomically thin Rhenium disulfide (ReS2), we observed interesting low-symmetry-induced anisotropic transport and mechanical properties, and studied their electronic and optoelectronic applications.[1] In type-II Weyl semimetal Tungsten ditelluride (WTe2), we observed planar-orientation-dependent negative longitudinal magnetoresistance (MR) which reveals important transport signatures of chiral anomaly and type-II Weyl fermions.[2] In the second part of my talk, I will show that 2D heterostructures could play important roles in future advanced memory, computing and optoelectronic applications. One example is robust memristors with good thermal stability based on a 2D heterostructure composed of graphene/MoS2–xOx/graphene, which show promising memory and neuromorphic applications.[3] Our latest results on the observation of ballistic avalanche phenomena in a thin 2D heterostructure made of black phosphorus and Indium Selenide (InSe), as well as their high-performance electronic and optoelectronic applications will also be presented.[4] |
Monday, March 2, 2020 5:18PM - 5:30PM |
D57.00011: Graphene/hBN vertical transistor : tuning a tunneling barrier height by modulating fermi energy level of graphene Jun-Ho Lee, Dong Hoon Shin, Heejun Yang, Nae Bong Jeong, Do-Hyun Park, Kenji Watanabe, Takashi Taniguchi, Sang Wook Lee, Sung-Ho Jhang, Bae Ho Park, Young Kuk, Hyun-Jong Chung Graphene is a 2-dimensional plane of carbon and a zero-band gap material whose conduction and valence band meet at dirac point. This electronic band structure makes it possible that the graphene's fermi energy level is modulated with accumulated charges by ~0.5 eV [1]. In this study, the unique property of graphene, large modulation of fermi energy level, was used to realize a vertical transistor which is based on graphene/hexagonal boron nitride (hBN) heterostructure. This device controlled tunneling barrier height between graphene and hBN by modulating the graphene's fermi energy level, and Ion/Ioff up to 106 was achieved at 300 K. We also confirmed that there was little change in performance of device at 300 K and 15 K. |
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