Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session X12: Devices from 2D Materials -- Advanced FabricationFocus
|
Hide Abstracts |
Sponsoring Units: DMP Chair: Cui-Zu Chang, Pennsylvania State University Room: BCEC 153A |
Friday, March 8, 2019 8:00AM - 8:36AM |
X12.00001: Interlayer Excitons in Transition Metal Dichalcogenides Heterostructures Invited Speaker: Xiaoqin (Elaine) Li In van der Waals heterostructures formed by stacking two monolayers of transition metal dichalcogenides, interlayer excitons with long recombination lifetime represent the lowest energy optical resonances. In heterostructures created by using different material recombinations and different fabrication methods, interlayer exciton properties are drastically different. I will discuss the observation of multiple interlayer exciton resonances with either positive or negative circularly polarized emission in a MoSe2/WSe2 heterobilayer with a small twist angle created using the mechanical exfoliation and stacking method. We attribute these resonances to the ground state and excited states confined within the moiré potential. I will compare these experiments to those observed in a MoSe2/WSe2 heterobilayer created using the chemical vapor deposition method. |
Friday, March 8, 2019 8:36AM - 8:48AM |
X12.00002: Top-down nanopatterning of layered transition metal dichalcogenide heterostructures Pufan Liu, Teodor Stanev, Kenji Watanabe, Takashi Taniguchi, Nathaniel Stern Nanostructured materials give rise to useful features such as size-dependent properties, interfacial phenomena, and edge effects, allowing optimization for opto-electronics. Although electron beam lithography has been widely used for top-down fabrication of nanostructures, translating this approach to the emerging class of 2D materials has challenges. Direct electron beam exposure on 2D materials can lead to non-reversible damage and degradation of optical and electronic properties. We show that e-beam damage can be significantly reduced on monolayer transition metal dichalcogenides by covering it with a thin hexagonal boron nitride layer. The reduced damage allows direct negative resist lithographic writing of sub-10nm nanostructure fabrication without impairing the monolayer optical and electrical properties. |
Friday, March 8, 2019 8:48AM - 9:00AM |
X12.00003: Optical Annealing of Graphene Oxide Thin Films Shashank ram Nandyala, Joseph Murphy, Michael A Seas, Vivek Santosh Jain, Subash Kattel, Jon M Pikal, Patrick A Johnson, John Ackerman, William Rice Graphene oxide (GO) can be converted to highly conductive reduced GO (rGO) via photochemical methods, solution chemistry, and high-temperature treatments. Specifically, highly localized, controllable laser-based annealing has been shown to create conductive patterns of rGO. This optically induced thermal transition is characterized by the ratio of sp2-to-sp3-hybridized carbon (using Raman spectroscopy) and electrical conductivity. Here, we show that circuit-like patterns of rGO can be created using a 532 nm laser at intensities of ~6 MW/cm2. Using the integrated ratio of the GO sp2 G-band (~1594 cm-1) to sp3 D-band (~1363 cm-1), we show that the optically generated GO-to-rGO conversion is slower and more uniform in an argon environment than in vacuum, an observation we attribute to the greater thermal exchange created by the high heat capacity argon gas. We determine the GO-to-rGO transition temperature of our optical process using the ratio of the integrated Stokes to anti-Stokes peaks and find that this temperature is consistent with standard induction furnace rGO annealing. Our findings suggest that optically created circuits of conductive rGO can be reproducibly created from GO films. |
Friday, March 8, 2019 9:00AM - 9:12AM |
X12.00004: One-Dimensional Potential in Graphene Apoorv Jindal, Avishai Benyamini, Sai Sunku, Yihang Zeng, Kenji Watanabe, Takashi Taniguchi, James Hone, Cory R Dean, Dimitri Basov, Abhay Pasupathy With improvements in fabrication techniques, low-disorder graphene devices have been realized to study a variety of correlated physics including fractional quantum Hall effect, and Mott insulating behavior. One possibility for inducing new electronic phenomena is by the use of nanometer-scale one-dimensional potentials to define narrow channels in graphene sheets. Previous efforts to study such effects in graphene have relied on lithographic fabrication of narrow metal gates. Lithographic methods suffer from edge disorder and a resolution limited to tens of nanometers. In this talk, we describe the engineering of a 1D potential in graphene using a carbon nanotube (CNT) that is a few nanometers from the graphene surface. We will describe cryogenic magnetotransport measurements that indicate the presence of a one-dimensional mode in graphene under appropriate gating conditions from the CNT. |
Friday, March 8, 2019 9:12AM - 9:24AM |
X12.00005: Two dimensional SrTiO3 membranes Wei Guo, Agham Posadas, Alexander Demkov, Anupam Roy, Amritesh Rai, omar Mohammed, Sanjay Banerjee, Kevin Olsson, Xiaoqin (Elaine) Li Perovskite SrTiO3 (STO) exhibits a wide range of exciting phenomena in addition to being a common substrate in epitaxial growth of various oxides like LaAlO3, BaTiO3, etc. There is a growing interest in studying new physical phenomena happens in the oxide materials in the two dimensional limit. We developed an etching method to fabricate free-standing STO membranes. The membranes are typically 5-8 um wide and 10-20 um long with thickness ranging from two to several tens of nanometers. We use Micro-Raman spectroscopy to investigate the STO membranes’ vibrational spectra and compare with that of the bulk STO. To exploit the high dielectric constant of STO, we design and fabricate electronic devices combining STO membranes with other two dimensional materials such as graphene and h-BN. |
Friday, March 8, 2019 9:24AM - 9:36AM |
X12.00006: Lithographically-defined strain control in atomically-thin semiconductors Leo Yu, Jingyuan Linda Zhang, Sven Borghardt, Minda Deng, Geun Ho Ahn, Jelena Vuckovic, Tony F Heinz Frontier quantum science calls for a large-scale deployment of solid-state artificial atoms, or quantum dots (QDs). But the progress has been limited due to the lack of simultaneous control of a material’s bandgap spatially and in energy. Here, we present a new approach based on lithographically-defined strain to achieve control of both the spatial position and bandgap energy in atomically-thin semiconductors. In our method, we first suspend a monolayer over a nanoscale cavity in the substrate; we then deform the layer using high-pressure gas, atomic force microscopy or thermal molding. With an optimized new process, we have produced localized biaxial strain down to 40-nm widths at defined positions in a WSe2 monolayer and in other atomically-thin semiconductors. Tensile strains up to 3.5% have been achieved by appropriate design of the cavity depth and can be maintained without any external pressure or voltage. Because of the strain-induced reduction in the bandgap, these QDs exhibit emission peaks spectrally separated from the intrinsic peaks by more than 100 meV. We discuss potential applications of such localized QD structures in 2D semiconductors. |
Friday, March 8, 2019 9:36AM - 9:48AM |
X12.00007: Design of Nanocarbon Electronic Devices for Single-Molecule Measurements Amira Bencherif, Richard Martel, Delphine Bouilly With the miniaturization of electronics, it is now possible to assemble field-effect transistors (FET) with single-molecule components as channel or gate. Single-molecule FETs have been recently used to study different fundamental mechanisms at the individual molecule scale, such as charge transport, folding and chemical reactions, both for small molecules and complex biological macromolecules. Here, our goal is to use nanocarbon materials (graphene or carbon nanotubes) to design and fabricate FET architectures suitable for single-molecule measurements. First, we report the fabrication of large arrays of FET devices with similar electrical characteristics, built from long carbon nanotubes or large-area graphene synthesized by chemical vapor deposition (CVD).Second, we used electron-beam lithography to pattern high-resolution features (20nm), in order to design nanoconstrictions in the graphene channel, as well as nanofluidic cavities allowing for single-point reaction chemistry. We will present the electrical characteristics of these devices, as well as high-resolution imaging using scanning electron and atomic force microscopy (SEM/AFM). Finally, we will discuss future work in terms of single-molecule functionalization with biological molecules. |
Friday, March 8, 2019 9:48AM - 10:00AM |
X12.00008: Resonance Behavior of Graphene Resonators with Various Periodic Hole Pattern Min Hee KWON, Dong Hoon Shin, Junhee Choi, Juhee Yoon, Sang Wook Lee In this presentation, the mechanical resonance behaviors of porous graphene resonator used for were studied. The goal of this research is to find an optimal geometric structure of drum-like graphene for with obtaining its mechanical resonance with high frequencies and high Q-factors. Resonance behavior of graphene drums with various periodic hole-patterns has been studied by using finite element modeling simulation. The geometry and number of hole structures on graphene were designed and fabricated according to the simulation modeling. Our simulation results suggest that the resonance frequency of the graphene drum gradually increases and then drops as the number of pores of the graphene increases from 0 to 100. In addition, the porous graphene resonator devices are experimentally realized by transferring a porous graphene membrane on substrate with a trench structure. Experimentally measured resonance frequencies and estimated quality factors of graphene resonator with various pore structures were compared to and analyzed by simulation results. |
Friday, March 8, 2019 10:00AM - 10:12AM |
X12.00009: Barristor device based on graphene and carbon nanotube junction Younggyu You, Jun-Ho Lee, Inchul Choi, Do-Hyun Park, Hyun-Jong Chung, Sung-Il Jo, Goo-Hwan Jeong, 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 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 meV/dec with high current density. This all-carbon device can be useful to graphene logic circuit, flexible electronics circuit and memory device. |
Friday, March 8, 2019 10:12AM - 10:24AM |
X12.00010: Maximizing Alloy Graphene Interface Conductance Dipanjan Saha, Xiaoxiao Yu, Zhitao Guo, Nicholas Golio, Mohamed Darwish, Yunus Kesim, Jeffrey Weldon, Andrew Gellman, Jonathan A Malen We present high throughput thermal conductance data at alloy/graphene interfaces as a function of alloy composition and adhesion layer thickness, with a maxima observed at 10 at. % Pd in Ni without an adhesion layer. Graphene contact research has been exclusively limited to pure metals, where the metal/graphene interface inhibits the flow phonons, quantified by the thermal interface conductance. For future electronics to fully capitalize on the revolutionary transport properties of graphene, sufficient heat dissipation at the contact interface is critical to performance. [1] |
Friday, March 8, 2019 10:24AM - 10:36AM |
X12.00011: Mixed-dimensional vdW heterostructure optoelectronic devices using p-MoS2 nanosheets Pan Li, Yu Ye, Lun Dai The advent of two-dimensional (2D) van der Waals (vdW) heterostructures, enabling the engineering of the heterostructure band alignment and resultant interfacial physical properties, has attracted strong scientific interest. The vdWs heterostructures provide the promise for developing novel near-infrared (NIR) optoelectronic devices, which play an important role in military, telecommunication, healthcare and so on. Moreover, the construction of the mixed-dimensional van der Waals (vdW) heterostructures with two-dimensional (2D) and one-dimensional (1D) materials can advantageously integrate their respective dimensional properties to produce new device functionalities and/or enhance device performance. In this talk, we report a LED based on a p-type MoS2 nanosheet and an n-type CdSe NW, with strong electroluminescence centered at ∼709 nm. This novel 2D/1D vdW heterostructure, which takes advantages of both 2D and 1D semiconductors, enables potential future applications in electrically driven lasers, high-sensitivity sensors, and transparent flexible devices. We also report a NIR LED and self-powered photodetector device based on p-MoS2/n-InSe vdWs heterostructures. |
Friday, March 8, 2019 10:36AM - 10:48AM |
X12.00012: Quantum point contact in bilayer graphene Hailong Fu, Jing Li, Ya-Wen Chuang, Kenji Watanabe, Takashi Taniguchi, Jun Zhu Edge state interferometry has been an important tool in probing the charge and statistics of elementary excitations of the quantum Hall and fractional quantum Hall effect of a two-dimensional electron gas. The recent observations of a plethora of fractional quantum Hall states in bilayer graphene, especially a series at even denominators, made this technique all the more appealing. A quantum point contact (QPC) is a key component of an interferometer, the realization of which is difficult in graphene owing to its gapless nature. In bilayer graphene, a pair of aligned top and bottom gates[1, 2] can be used to open a band gap and therefore construct a QPC. Here we report on our effort in fabricating QPC devices using high-quality h-BN encapsulated bilayer graphene. Because of the thin gating profile, the confining potential of the QPC in bilayer graphene is much sharper than what can be achieved in GaAs 2D systems. We observed well-developed quantum Hall states across QPCs with large openings and gate-controlled backscattering of edge states in QPCs with smaller openings. We discuss our fabrication processes, challenges and progress towards a Fabry-Perot interferometer in bilayer graphene. |
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