Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session A31: Carbon Nanotubes and Related Materials: Transport and DevicesFocus
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Sponsoring Units: DMP Chair: Masahiro Ishigami, University of Central Florida Room: 294 |
Monday, March 13, 2017 8:00AM - 8:36AM |
A31.00001: Understanding the physics that causes hysteresis in carbon nanotube transistors, a key step toward high performance and energy-efficiency Invited Speaker: Rebecca Park Three-dimensional (3D) integration is a promising technology that achieves higher energy efficiency, higher performance, and smaller footprint than today's planar, 2D technology [1]. In particular, carbon nanotube field-effect transistors (CNFETs) enable monolithic 3D integration due to its low-temperature processing (\textless 400 $^{\circ}$ C) [2]. Although CNFETs promise high-performance and energy-efficient digital systems, large hysteresis has long remained a challenge. Our approach to eliminating hysteresis is based on our understanding of the physics that lead to hysteresis [3]:\\ \\Understanding the sources of hysteresis: We develop a novel measurement technique called the Pulsed Time-Domain Measurement (PTDM) which enables quantification of charged traps responsible for hysteresis. Leveraging a physics-based model, we study the mechanism of the charge trapping process.\\ \\Eliminating hysteresis: After gaining a deeper understanding of the sources of hysteresis, we are able to develop a VLSI-compatible, solid-state fabrication method that mitigates the effect of traps. On average, we achieve hysteresis of less than 0.5{\%} of the gate-source voltage sweep range. \newline \newline Reference: \newline [1] M.M. Sabry Aly, M. Gao, G. Hills, C.-S. Lee, G. Pitner, M.M. Shulaker, T.F. Wu, M. Asheghi, J. Bokor, F. Franchetti, K.E. Goodson, C. Kozyrakis, I. Markov, K. Olukotun, L. Pileggi, E. Pop, J. Rabaey, C. Re, H.-S. P. Wong, S. Mitra, "Energy-Efficient Abundant-Data Computing: The N3XT 1,000X," IEEE Computer, pp. 24 -- 33, December 2015\newline [2] M. Shulaker, T. Wu, A. Pal, K. Saraswat, H.-S. P. Wong, S. Mitra, ``Monolithic 3D Integration of Logic and Memory: Carbon Nanotube FETs, Resistive RAM, and Silicon FETs,'' IEEE International Electron Devices Meeting (IEDM), paper 27.4, pp. 638 -- 641, December 15 -- 17, San Francisco, 2014 \newline [3] R. S. Park, M. M. Shulaker, G. Hills, L. S. Liyanage, S. Lee, A. Tang, S. Mitra, H.-S. P. Wong, "Hysteresis in Carbon Nanotube Transistors: Measurement and Analysis of Trap Density, Energy Level, and Spatial Distribution," ACS Nano 10, pp. 4599 -- 4608, March2016 [Preview Abstract] |
Monday, March 13, 2017 8:36AM - 8:48AM |
A31.00002: High Efficiency Carbon Nanotube Thread Antennas Elie Bengio, Damir Senic, Lauren Taylor, Dmitri Tsentalovich, Peiyu Chen, Christopher Holloway, David Novotny, Aydin Babakhani, Christopher Long, James Booth, Nathan Orloff, Matteo Pasquali Although previous research has explored the underlying theory of high-frequency behavior of carbon nanotubes (CNTs) and CNT bundles for antennas, there is a gap in the literature for direct experimental measurements of radiation efficiency. Here we report a novel measurement technique to accurately characterize the radiation efficiency of quarter-wavelength monopole antennas made from CNT thread. At medical device (1 GHz) and Wi-Fi (2.4 GHz) frequencies, we measured the highest absolute values of radiation efficiency in the literature for CNT antennas, matching that of copper wire. We also report the first direct experimental observation that, contrary to metals, the radiation efficiency of the CNT thread improves significantly at higher frequencies. These results pave the way for practical applications of CNT thread antennas, particularly in the aerospace and wearable electronics industries where weight saving is a priority. [Preview Abstract] |
Monday, March 13, 2017 8:48AM - 9:00AM |
A31.00003: Electrostatic and chemical doping of C60-filled nanotubes Wu Shi, Hamid Barzagar, Seita Onishi, Alex Zettl C60-filled nanotubes, known as fullerene peapods, have attracted considerably interest for many years not only because of their peculiar hybrid structures but also due to their anticipated unique electronic properties and potential applications, such as memory effects and high temperature superconductivity. However, the superconducting or even truly metallic behavior has not yet been achieved. In this study, we use both the electrostatic and chemical methods to effectively dope the C60-filled nanotubes and modulate their transport properties. TEM characterization and low temperature transport results on these doped samples will be presented. [Preview Abstract] |
Monday, March 13, 2017 9:00AM - 9:36AM |
A31.00004: Wafer-scale, massively parallel carbon nanotube arrays for realizing field effect transistors with current density exceeding silicon and gallium arsenide Invited Speaker: Michael Arnold Calculations have indicated that aligned arrays of semiconducting carbon nanotubes (CNTs) promise to outperform conventional semiconducting materials in short-channel, aggressively scaled field effect transistors (FETs) like those used in semiconductor logic and high frequency amplifier technologies. These calculations have been based on extrapolation of measurements of FETs based on one CNT, in which ballistic transport approaching the quantum conductance limit of 2$G_{o}=$4e$^{\mathrm{2}}$/h has been achieved. However, constraints in CNT sorting, processing, alignment, and contacts give rise to non-idealities when CNTs are implemented in densely-packed parallel arrays, which has resulted in a conductance per CNT far from 2$G_{o}$. The consequence has been that it has been very difficult to create high performance CNT array FETs, and CNT array FETs have not outperformed but rather underperformed channel materials such as Si by 6$x$ or more. Here, we report nearly ballistic CNT array FETs at a density of 50 CNTs um$^{\mathrm{-1}}$, created via CNT sorting, wafer-scale alignment and assembly, and treatment. The on-state conductance in the arrays is as high as 0.46 $G_{o}$ per CNT, and the conductance of the arrays reaches 1.7 mS um$^{\mathrm{-1}}$, which is 7$x$ higher than previous state-of-the-art CNT array FETs made by other methods. The saturated on-state current density reaches 900 uA um$^{\mathrm{-1}}$ and is similar to or exceeds that of Si FETs when compared at equivalent gate oxide thickness, off-state current density, and channel length. The on-state current density exceeds that of GaAs FETs, as well. This leap in CNT FET array performance is a significant advance towards the exploitation of CNTs in high-performance semiconductor electronics technologies. $^{\mathrm{\ast }}$Brady GJ, Way AJ, Safron NS, Evensen HT, Gopalan P, Arnold MS, Quasi-ballistic carbon nanotube array transistors with current density exceeding Si and GaAs, SCIENCE ADVANCES, 2 (9), e1601240 (2016) [Preview Abstract] |
Monday, March 13, 2017 9:36AM - 9:48AM |
A31.00005: Selective burning of metallic single-walled carbon nanotubes for integration of transistors Keigo Otsuka, Taiki Inoue, Shohei Chiashi, Shigeo Maruyama High-density arrays of semiconducting single-walled carbon nanotubes (s-SWNTs) are promising building blocks for next-generation digital systems. Since direct growth of SWNTs on single-crystal substrates offers excellent alignment and cleanliness, much effort has been made to avoid short circuits derived from metallic SWNTs (m-SWNTs) by selective etching from as-grown aligned SWNTs. Although electrical breakdown is a powerful tool because of high selectivity of the removal and compatibility with high-density SWNTs, it would remarkably degrades on-current in ultrascaled devices because extremely high field is required to cut SWNTs. We propose a method for full-length burning of m-SWNTs triggered by Joule self-heating toward pure s-SWNT arrays and integration of transistors. The burning of SWNTs was enhanced by polymer coating and additional water vapor. The burning length was increased from 100 nm to 5.5 um (half of the SWNT length) on average. We found the burning length was restricted by one-way burning from breakdown position, where oxidation occurred first. By controlling the breakdown position, nearly full-length burning was achieved for all m-SWNTs. Multiple transistors were fabricated along the obtained s-SWNT arrays, showing excellent performance. [Preview Abstract] |
Monday, March 13, 2017 9:48AM - 10:00AM |
A31.00006: Room temperature single photon generation at 1. 5 $\mu$ m from covalent dopant states of carbon nanotubes Han Htoonb, Xiaowei He, Nicolai Hartmann, Xuedan Ma, Stephen Doorn Recent demonstration that oxygen dopant states covalently attached to the single-walled carbon nanotubes (SWCNTs) are capable of emitting single photons at room-T (RT) opens the possibility of building room-T electrically-driven single photon sources for quantum communication applications.$^{\mathrm{1}}$ The RT single photon generation was not observed only at wavelength beyond 1.3 $\mu$ m. Here in this work we demonstrate RT single photon generation at 1. 5 $\mu$ m from diazonium dopant states of (10,3) nanotubes. $^{\mathrm{1}}$ Ma, Xuedan. et al. Nature Nanotech. 2015, 10, 671 [Preview Abstract] |
Monday, March 13, 2017 10:00AM - 10:12AM |
A31.00007: Single photon generation through exciton-exciton annihilation in air-suspended carbon nanotubes Akihiro Ishii, Takushi Uda, Yuichiro K. Kato Carbon nanotubes have great potential for single photon sources as they have stable exciton states even at room temperature and their emission wavelengths cover the telecommunication bands. In recent years, single photon emission from carbon nanotubes has been achieved by creating localized states of excitons. In contrast to such an approach, here we utilize mobile excitons and show that single photons can be generated in air-suspended carbon nanotubes, where exciton diffusion length is as long as several hundred nanometers and exciton-exciton annihilation is efficient.\footnote{A. Ishii et al. Phys. Rev. B 91, 125427 (2015).} We perform photoluminescence microscopy on as-grown air-suspended carbon nanotubes in order to determine their chirality and suspended length. Photon correlation measurements are performed on nanotube emission at room temperature using a Hanbury-Brown-Twiss setup with InGaAs/InP single photon detectors. We observe antibunching with a clear excitation power dependence, where we obtain $g^{(2)}(0)$ value less than 0.5 at low excitation powers, indicating single photon generation. We show such $g^{(2)}(0)$ data with different chiralities and suspended lengths, and the effects of exciton diffusion on single photon generation processes are discussed. [Preview Abstract] |
Monday, March 13, 2017 10:12AM - 10:24AM |
A31.00008: An electronic beam splitter realized with crossed graphene nanoribbons Thomas Frederiksen, Pedro Brandimarte, Mads Engelund, Nick Papior, Aran Garcia-Lekue, Daniel Sanchez-Portal Graphene nanoribbons (GNRs) are promising components in future nanoelectronics. We have explored a prototype 4-terminal semiconducting device formed by two crossed armchair GNRs (AGNRs) using state-of-the-art first-principles transport methods.\footnote{P. Brandimarte et al., arXiv:1611.03337} We analyze in detail the roles of intersection angle, stacking order, inter-GNR separation, and finite voltages on the transport characteristics. Interestingly, when the AGNRs intersect at $\theta=60^\circ$, electrons injected from one terminal can be split into two outgoing waves with a tunable ratio around 50$\%$ and with almost negligible back-reflection. The splitted electron wave is found to propagate partly straight across the intersection region in one ribbon and partly in one direction of the other ribbon, i.e., in analogy of an optical beam splitter. Our simulations further identify realistic conditions for which this semiconducting device can act as a mechanically controllable electronic beam splitter with possible applications in carbon-based quantum electronic circuits and electron optics. [Preview Abstract] |
Monday, March 13, 2017 10:24AM - 10:36AM |
A31.00009: Selective sensing of ethylene and glucose using carbon-nanotube-based sensors: An ab initio investigation Yan Li, Miroslav Hodak, Wenchang Lu, Jerry Bernholc Functionalized carbon nanotubes have great potential for nanoscale sensing applications, yet many aspects of their sensing mechanisms are not understood. We investigate two paradigmatic sensor configurations for detection of biologically important molecules through ab initio calculations: a non-covalently functionalized nanotube for glucose detection and a covalently functionalized nanotube for ethylene detection. Despite of their structural and chemical simplicities, glucose and ethylene control key life processes of humans and plants, respectively. We evaluate the sensors' electrical conductance and transmission coefficients at the full density-functional theory level via the non-equilibrium Green's function method. A clear atomistic picture emerges about the mechanisms involved in glucose and ethylene sensing. While functionalized semiconducting nanotubes exhibit good sensitivities in both cases, the current through metallic nanotubes is only weakly affected by analyte attachment. We also investigate the effects of band gaps of the nanotubes and changes to the receptors on the detection sensitivities. These quantitative results can guide the design of improved sensors. [Preview Abstract] |
Monday, March 13, 2017 10:36AM - 10:48AM |
A31.00010: Room temperature stable single molecule rectifiers with graphite electrodes Ivan Rungger, V. Kaliginedi, A. Droghetti, H. Ozawa, A. Kuzume, M. Haga, P. Broekmann, A. V. Rudnev In this combined theoretical and experimental study we present new molecular electronics device characteristics of unprecedented stability at room temperature by using electrodes based on highly oriented pyrolytic graphite with covalently attached molecules. To this aim, we explore the effect of the anchoring group chemistry on the charge transport properties of graphite/molecule contacts by means of the scanning tunneling microscopy break-junction technique and ab initio simulations. The theoretical approach to evaluate the conductance is based on density functional theory calculations combined with the non-equilibrium Green’s function technique, as implemented in the Smeagol electron transport code \footnote{A. Rocha et al., Nature Mater. {\bf 4}, 335 (2005); A. Rocha et al., Phys. Rev. B {\bf 73}, 085414 (2006); I. Rungger et al., Phys. Rev. B {\bf 78}, 035407 (2008)}. We also demonstrate a strong bias dependence and rectification of the single molecule conductance induced by the anchoring chemistry in combination with the very low density of states of graphite around the Fermi energy. We show that the direction of tunneling current rectification can be tuned by anchoring group chemistry. [Preview Abstract] |
Monday, March 13, 2017 10:48AM - 11:00AM |
A31.00011: Ballistic thermophoresis on graphene Erio Tosatti, Emanuele Panizon, Roberto Guerra The textbook thermophoretic force acting on a diffusing body in a fluid is proportional to the local temperature gradient. Not so for a diffusing physisorbed body on a submicron sized 2D suspended layer. A non-equilibrium Molecular Dynamics study of a test nanosystem - a gold nanocluster adsorbed on a single graphene sheet of length $L$ clamped between two temperatures $\Delta T $ apart - reveals a phoretic force that is parallel to, but essentially independent of, the gradient magnitude $\Delta T / L$ up to a substantial $L$ of up to 150 nm. This is argued to represent ballistic thermophoresis, where the force is provided by the flux of massively excited flexural phonons, whose flow is in turn known to be ballistic and distance-independent up to relatively long scattering lengths before the eventual onset of the more standard diffusive regime. The surprising thrust and real momentum provided by the flexural modes are analysed and understood in terms of the large mass non-uniformity involved with these modes. The ensuing surf-riding of adsorbates on the vibrating 2D hard sheet, and the resulting gradient independent thermophoretic force, are not unlikely to possess practical applications. [Preview Abstract] |
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