Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session X16: Two-Dimensional Material Heterostructures |
Hide Abstracts |
Sponsoring Units: DCMP DMP Chair: Masa Ishigami, University of Central Florida Room: 315 |
Friday, March 18, 2016 8:00AM - 8:12AM |
X16.00001: Interlayer Hybridization in van der Waals Heterostructures. Nam Le, Huan Tran, Lilia Woods Van der Waals heterostructures composed of chemically inert dissimilar layers are of great interest for fundamental science and applications. The weak interplanar interactions and orbital overlap are expected to bring modifications to the constituent materials. By using first principles simulations, we investigate the properties of several heterostructures, including graphene/silicene, graphene/MoS2, and silicene/MoS2. The calculations reveal superlattice characteristic points in the Brillouin zone associated with the different stacking patterns. Band structures projected on each of the constituents show hybridization features related to specific orbital overlap for each heterostructure. Phonon dispersion spectra for the considered heterostructures are also investigated. [Preview Abstract] |
Friday, March 18, 2016 8:12AM - 8:24AM |
X16.00002: Vertically Stacked Graphene/Transition-Metal-Dichalcogenides/Graphene Heterojunction Devices for High Performance Photodetectors Jinseong Heo, Heejeong Jeong, Jaeho Lee, Kiyoung Lee, Eun-Kyu Lee, Sangyeob Lee, Yeonchoo Cho, Kyung-Eun Byun, Chang-Won Lee, Seongjun Park, Sungwoo Hwang Photodetectors based on vertically stacked graphene heterojunctions have advantages of short transit length for photo-generated carriers and large sensing area, thus implying fast response time and high responsivity. Previously, vertically stacked Graphene (Gr)/Transition-Metal-Dichalcogenide (TMDC)/Gr junctions were introduced for optoelectronic devices, showing high current on and off ratio as well as photoresponsivity. But for high performance photodetectors, both thorough and comparative study in terms of the figures of merit such as photoresponse time and photoresponsivity depending on different TMDC materials is crucial. Here, we report fast response time (28 us) and high responsivity (20 A/W) from Gr/WSe2 and MoS2/Gr, respectively. At the same time, those devices operate as p- and n-type barrier-variable transistors, respectively, being a potential building block for optoelectronic system on a chip. [Preview Abstract] |
Friday, March 18, 2016 8:24AM - 8:36AM |
X16.00003: Ab initio Mapping of Interlayer Coupling in Transition Metal Dichalcogenides and Graphene Shiang Fang, Efthimios Kaxiras Two-dimensional layered materials cover a wide variety of physics phenomena, such as topological phases, superconductivity, magnetism and charge density waves. Owing to the layered geometry and the van der Waals interactions in between, stacks of these van der Waals layered materials provide a venue to create a heterostructure with various physics properties. The interaction between different physics properties is particular interesting to engineer the material with the desired properties. One of the crucial ingredient in understanding the heterostructure is the interlayer coupling in between. In the literature, such kind of coupling has been proposed in various empirical forms. However, a true ab initio coupling model is still lacking. For the first time, here we have derived such interlayer coupling model from the first principle calculations based on the Wannier transformation of graphene stacks. We further investigate the Fermi velocity renormalization, van Hove singularities and the moire pattern for electron localization. Such microscopic understanding of the interlayer coupling would shed light on orbital hybridization and transport in multilayer stacks. [Preview Abstract] |
Friday, March 18, 2016 8:36AM - 8:48AM |
X16.00004: The Interlayer Resistance of a Misoriented Bilayer MoS2 Interface Kuan Zhou, Darshana Wickramaratne, Supeng Ge, Roger Lake The performance of electrical and opto-electronic devices with vertically stacked transition metal dichalcogenides (TMDCs) has been found to be degraded by the rotated interface between bilayer system.The band properties and interlayer coupling have been researched experimentally and computationally, however, the dependence of the interlayer resistance on the disorientation angle of the two layers forming bilayer MoS2 remains unknown. Ab-initio methods combined with non-equilibrium Greens functions are used to calculate the transport properties of the misoriented bilayer MoS2 system. The energy and angle dependence of the interlayer resistivity is determined. The difference between the electron and hole transmission properties is analyzed. The influence of spin polarization in the K valleys of the TMDC system is also been discussed. [Preview Abstract] |
Friday, March 18, 2016 8:48AM - 9:00AM |
X16.00005: Probing in-plane anisotropy and interlayer interactions in ReS$_2$ and ReSe$_2$ by Raman spectroscopy Etienne Lorchat, Guillaume Froehlicher, St\'ephane Berciaud We address the intriguing Raman response of rhenium disulfide (ReS$_2$) and rhenium diselenide (ReSe$_2$). These layered semiconductors belong to the family of transition metal dichalcogenides and exhibit significant in-plane anisotropy and can be represented as a distorted $1T$-phase (octahedral), with considerably lower symmetry than the more extensively studied $2H$-phase (trigonal prismatic) compounds based on molybdenum or tungsten. Nevertheless, we will demonstrate that the low-frequency rigid layer vibrational modes of $N$-layer ReS$_2$ and ReSe$_2$ can, on the one hand, be described using a linear chain model but, on the other hand, make it possible to directly probe the in-plane anisotropy and to determine the crystal orientation. Since in-plane anisotropy also has a direct impact on the optical and electron transport properties, our work opens avenues for engineering novel optoelectronic devices relying on ReS$_2$ and ReSe$_2$. [Preview Abstract] |
Friday, March 18, 2016 9:00AM - 9:12AM |
X16.00006: Twisted Van der Waals Systems Satrio Gani, Enrico Rossi Van der Waals systems formed by two-dimensional (2D) crystals and nanostructures possess electronic properties that make them extremely interesting for basic science and for possible technological applications. By tuning the relative angle (the twist angle) between the layers, or nanostructures, forming the Van der Waals systems experimentalists have been able to control the stacking configuration of such systems. We study the dependence on the twist angle of the electronic properties of two classes of Van der Waals systems: double layers formed by two, one-atom thick, layers of a metal dichalcogenide such as molybdenum disulfide (${\rm MoS_2}$), and graphene nanoribbons on a hexagonal boron nitride substrate. We present results that show how, for both classes of systems, the electronic properties can be strongly tuned via the twist angle. [Preview Abstract] |
Friday, March 18, 2016 9:12AM - 9:24AM |
X16.00007: \textbf{Epitaxial MoS}$_{\mathrm{\mathbf{2}}}$\textbf{/GaN structures to enable vertical 2D/3D semiconductor heterostructure devices} D. Ruzmetov, K. Zhang, G. Stan, B. Kalanyan, S. Eichfeld, R. Burke, P. Shah, T. O'Regan, F. Crowne, A.G. Birdwell, J. Robinson, A. Davydov, T. Ivanov MoS$_{\mathrm{2}}$/GaN structures are investigated as a building block for vertical 2D/3D semiconductor heterostructure devices that utilize a 3D substrate (GaN) as an active component of the semiconductor device without the need of mechanical transfer of the 2D layer. Our CVD-grown monolayer MoS$_{\mathrm{2}}$ has been shown to be epitaxially aligned to the GaN lattice which is a pre-requisite for high quality 2D/3D interfaces desired for efficient vertical transport and large area growth. The MoS$_{\mathrm{2}}$ coverage is nearly 50 {\%} including isolated triangles and monolayer islands. The GaN template is a double-layer grown by MOCVD on sapphire and allows for measurement of transport perpendicular to the 2D layer. Photoluminescence, Raman, XPS, Kelvin force probe microscopy, and SEM analysis identified high quality monolayer MoS$_{\mathrm{2}}$. The MoS$_{\mathrm{2}}$/GaN structures electrically conduct in the out-of-plane direction and across the van der Waals gap, as measured with conducting AFM (CAFM). The CAFM current maps and I-V characteristics are analyzed to estimate the MoS$_{\mathrm{2}}$/GaN contact resistivity to be less than 4 $\Omega $-cm$^{\mathrm{2}}$ and current spreading in the MoS$_{\mathrm{2}}$ monolayer to be approx. 1 $\mu $m in diameter. Epitaxial MoS$_{\mathrm{2}}$/GaN heterostructures present a promising platform for the design of energy-efficient, high-speed vertical devices incorporating 2D layered materials with 3D semiconductors. [Preview Abstract] |
Friday, March 18, 2016 9:24AM - 9:36AM |
X16.00008: ABSTRACT WITHDRAWN |
Friday, March 18, 2016 9:36AM - 9:48AM |
X16.00009: Raman spectrum of MoS2/WS2 heterostructure from first-principles calculation of phonon electron coupling Jun Jiang, Xiaoguang Zhang, Liangbo Liang, Georgios D. Barmparis, Yevgeniy S. Puzyrev, Sokrates T. Pantelides We present a first-principles method to calculate Raman spectrum of MoS2/WS2 heterostructure due to electron excitation. The first step is to calculate the ground state phonon modes and the displacements of the atoms from the ground state to the excited states. In the next step, Inelastic multi-phonon relaxation for the excited electron is considered to produce the Raman spectrum quantitatively. The relative Raman intensity, peak width and shape are obtained directly from a sum over trillions of configurations of multiple phonon modes using a Monte Carlo scheme. Alternatively, we also calculate the overlap between the ground state phonon mode eigenvectors and the excited state atomic displacements, which provides a quick and qualitative description for the Raman shifting due to electron excitation. [Preview Abstract] |
Friday, March 18, 2016 9:48AM - 10:00AM |
X16.00010: Optical properties of few-layer MoS2-based heterostructures Asma Alkabsh, Hassana Samassekou, Andrew Walker, Dipanjan Mazumdar, Saikat Talapatra 2D materials such as Transition metal dichalcogenides (TMDs) are promising for a number of electronic/optoelectronic applications. In particular, semiconducting MoS2, is considered as one of the most interesting 2D material due to its direct band gap at the monolayer level [1]. For device applications, such desirable properties have to translate when MoS2 is layered with other materials and substrates. In this research, the optical properties of select MoS2-based heterostructres are investigated. In particular, the effect of various insulating underlayers such as BN, SiO2 on few-layer MoS$_{\mathrm{2}}$ are examined using spectroscopic ellipsometry. The angles $\Psi $ and $\Delta $, as well as layer specific optical constants such as extinction coefficient (k) and refractive index (n) shall be extracted using Tauc-Lorentz oscillator model and as a function of MoS2 layer thickness and underlayer structure. The band gap properties of few-layer MoS2 will be analyzed using optical spectroscopy [Preview Abstract] |
Friday, March 18, 2016 10:00AM - 10:12AM |
X16.00011: The vertical transport properties of misoriented graphene/hexagonal-boron-nitride/graphene heterostructure devices Supeng Ge, Masum Habib, Roger Lake Hexagonal boron nitride (hBN) has an atomically smooth surface free of dangling bonds, minimal lattice mismatch with graphene and a wide band gap, which makes it an ideal insulator material for graphene devices. Recently, transistor devices made with the few layers of hBN sandwiched between two layers of graphene has attracted attention since interesting phenomenon such as negative differential resistance has been observed. In experiment, the device fabrication usually gives rise to random orientation of interfaces. To have a better understanding of the effect of misorientation, we employed non-equilibrium Greens function (NEGF) method to calculate transmission across graphene/hBN/graphene hererostructures devices. We find that the rotation can cause the transmission to change by more than one order of magnitude. The resistance and current as functions of h-BN layer thickness, commensurate rotation angles, gating voltage, and bias voltage are described. [Preview Abstract] |
Friday, March 18, 2016 10:12AM - 10:24AM |
X16.00012: Characterization of Graphene Transferred onto Hydrated "Soft" Substrates M. Blades, P. Vendola, W. Pierre, S. Jedlicka, S.V. Rotkin Graphene's unique properties have recently found application in the fields of biosensing and bioimaging. Substrate selection is an important step in the use of graphene for this purpose; however, choices are usually limited to hard, dry surfaces such as silicon dioxide. Here we demonstrate a modified procedure, based on the H2 bubbling method, for transferring graphene to the soft hydrogel polyacrylamide. Widefield imaging and confocal Raman mapping were performed to characterize the quality of the transfer. [Preview Abstract] |
Friday, March 18, 2016 10:24AM - 10:36AM |
X16.00013: The effects of quenched disorder on high-order sideband generation in GaAs/AlGaAs quantum wells Hunter Banks, Darren Valovcin, Shawn Mack, Arthur Gossard, Loren Pfeiffer, Mark Sherwin When a near-IR laser resonantly pumps excitons into a strong terahertz field, individual excitons tunnel ionize and the resulting electrons and holes are driven apart and then back together by the terahertz field. Resulting recollisions create a large number of sidebands around the pump frequency, in the process of high-order sideband generation (HSG) [1]. The high kinetic energy of the electron-hole recollisions yields substantial information about the underlying structure of the individual excitons as well as the interaction of energetic single electrons and holes with each other, the lattice, and quenched disorder at sub-micron length scales. We present a comparison of smooth-walled GaAs quantum wells with 5% AlGaAs quantum wells to illuminate the importance of scattering by imperfect crystals to HSG. The smaller scattering rates in the very clean quantum wells nearly double the number of observed sidebands, offering striking insight into this extremely nonlinear phenomenon. With a more complete understanding, HSG could be extended to more novel structures and materials. [1] B. Zaks, et al., Nature 483 (7391), 580 (2012) and H. Banks, et al., Physical Review Letters 111, 267402 (2013) [Preview Abstract] |
Friday, March 18, 2016 10:36AM - 10:48AM |
X16.00014: Passivation of CdSe Quantum Dots by Graphene and MoS2 Monolayer Encapsulation Datong Zhang, Dennis Zi-Ren Wang, Richard C. Creswell, Chenguang Lu, Irving P. Herman The encapsulation of a monolayer of CdSe quantum dots (QDs) by one-to-three layer graphene and MoS2 sheets protects the QDs from oxidation. Photoluminescence (PL) from the QD cores shows a much slower decrease in core diameter over time due to slower oxidation in regions where the QDs are covered by van der Waals (vdW) layers than in those where they are not, for chips stored both in the dark and in the presence of light. PL mapping shows that the CdSe QDs under the central part of the vdW sheet age slower than those near its edges, because oxidation of the covered QDs is limited by transport of oxygen from the edges of the vdW sheets and not transport across the vdW layers. This encapsulation effect is also tested with other environments. Preliminary results show that vdW materials could be promising candidates for nano-coating materials for devices operating in extreme environments. [Preview Abstract] |
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