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Author

Larry Epp

Other affiliations: Jet Propulsion Laboratory
Bio: Larry Epp is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Carbon nanotube & Resonator. The author has an hindex of 14, co-authored 36 publications receiving 1002 citations. Previous affiliations of Larry Epp include Jet Propulsion Laboratory.

Papers
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Journal ArticleDOI
TL;DR: In this article, a single-pole double-throw CNT switch was constructed with a sputtered Nb electrode and was measured to have switching times down to a few nanoseconds.
Abstract: Carbon nanotubes are attractive for switching applications since electrostatically-actuated CNT switches have low actuation voltages and power requirements, while allowing GHz switching speeds that stem from the inherently high elastic modulus and low mass of the CNT. Our first NEM structure, the air-bridge switch, consists of suspended single-walled nanotubes (SWNTs) that lie above a sputtered Nb electrode. Electrical measurements of these air-bridge devices show well-defined ON and OFF states as a dc bias of a few volts is applied. The switches were measured to have switching times down to a few nanoseconds. Our second NEM structure, the vertical CNT switch, consists of nanotubes grown perpendicular to the substrate. Vertical multi-walled nanotubes (MWNTs) are grown directly on a heavily doped Si substrate, from 200 – 300 nm wide, ~ 1 µm deep nano-pockets, with Nb metal electrodes to result in the formation of a vertical single-pole-double-throw CNT switch architecture.

6 citations

Proceedings ArticleDOI
04 May 2009
TL;DR: In this article, the phase noise of the Ka-band tube and solid-state amplifier additive phase noise performance was investigated for high-power Ka band amplifiers and the traveling wave tube amplifier (TWTA).
Abstract: A Ka-band (31–36GHz) solid state power amplifier (SSPA) capable of producing more than 50 W of output power was developed by the Jet Propulsion Laboratory (JPL) using a novel 32-way combiner/splitter and 32 2W GaAs PHEMT MMIC modules [1]. Additionally, a 200 W travelling wave tube amplifier (TWTA) manufactured by L3 Communications was acquired and characterized. While these devices are typically not the primary sources of origin for phase noise in transponders, they will contribute phase noise and may add to system phase noise differently. Because information on Ka-band tube and solid-state amplifier additive phase noise performance was not available for these high-power Ka-band amplifiers, an investigation into the phase noise of the SSPA and TWTA was launched. Results indicate that the tested SSPA may have a lower close-in phase noise than the tested TWTA.

5 citations

Proceedings ArticleDOI
18 Mar 2008
TL;DR: In this article, lateral CNT switches were demonstrated to operate at low voltages, low powers and high speeds at low power, low voltage, low power and high speed, and the insertion loss was < 0.5 dB at 100 GHz.
Abstract: Lateral CNT Switches: a) dc CNT switches were demonstrated to operate at low voltages, low powers and high speeds. b) RF simulations of switch in series configuration with metallized tube yielded good RF performance 1) Isolation simulated to be approx. 20 dB at 100 GHz. 2) Insertion loss simulated to be < 0.5 dB at 100 GHz. Vertical CNT Switches: a) Thermal CVD was used to mechanically constrain tubes in nanopockets; tubes not self-supporting. b) Demonstrated growth of vertically aligned arrays and single-few MWNTs using dc PECVD with Ni catalyst using optical lithography.

4 citations

Book ChapterDOI
01 Mar 2010
TL;DR: In this paper, the authors focus on the nanoelectronic applications of suspended carbon nanotubes, in particular their use as physical sensors and actuators, and describe the underlying motivation for using suspended CNTs as thermal conductivity based pressure sensors, and will describe in Section 2.2.
Abstract: Carbon is truly an extraordinary material with physical structures spanning threedimensional (3D) graphite, two-dimensional (2D) grapheme and zero-dimensional (0D) buckyballs or buckminster fullerine spheres. It is not surprising that the structural characteristics of carbon thus yield band diagrams displaying a diverse array of physical properties. When a 2D graphene sheet is rolled into a cylinder, a one-dimensional (1D) or quasi-1D form of carbon results, namely carbon nanotubes (CNTs), which have been one of the most extensively studied materials since their discovery (Ijima, 1991). A single rolled-up sheet of graphene results in a single-walled nanotube (SWNT) with a typical diameter of 1 – 2 nm. Multi-walled nanotubes (MWNTs) consist of concentric cylinders with an interlayer spacing of 0.3 – 0.4 nm, and diameters that are at least an order of magnitude larger than SWNTs, between 10 – 30 nm. The exceptional thermal, mechanical, electronic and optical properties of nanotubes (Dresselhaus, Dresselhaus, Avouris, 2001) has created a surge of applications, ranging from the use of CNTs as interconnects (Li et al., 2003), heat transport materials (Yu et al., 2006), novel transistors (Bachtold, et al. 2001), as well as optical materials (Homma et al., 2009). The focus of this chapter is on the nanoelectronic applications of suspended carbon nanotubes, in particular their use as physical sensors and actuators. Unlike 3D materials, when nanotubes are dispersed on a substrate, their properties are intimately influenced by the tube-to-substrate interactions, particularly those of SWNTs. For example, when diameter and helicity of SWNTs are controlled such that semiconducting tubes result (Odom et al., 1998), no luminescence is detected for SWNTs lying on a substrate eventhough semiconducting SWNTs have a direct band gap (Lefebvre et al., 2003). In addition, van der Waals interactions between CNTs and the substrate cause radial and axial deformations (Hertel et al., 1998) which affect the electron transport properties of the tubes. The presence of the substrate beneath the tube can also influence heat dissipation mechanisms, which is an underlying motivation for using suspended CNTs as thermal conductivity based pressure sensors, and will be described in Section 2.2. Such sensors are important for vacuum-based microcavity applications (vacuum microelectronics, microeletromechanical-systems (MEMS) such as gyroscopes and RF MEMS switches). The high

2 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, a review of the recent advances in nanotubes and nanotube-based composite sensors and actuators, with a particular emphasis on their electromechanical behavior is presented.

901 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that many of the commonly studied two-dimensional monolayer transition metal dichalcogenide (TMDC) nanoscale materials are piezoelectric, unlike their bulk parent crystals.
Abstract: We discovered that many of the commonly studied two-dimensional monolayer transition metal dichalcogenide (TMDC) nanoscale materials are piezoelectric, unlike their bulk parent crystals. On the macroscopic scale, piezoelectricity is widely used to achieve robust electromechanical coupling in a rich variety of sensors and actuators. Remarkably, our density-functional theory calculations of the piezoelectric coefficients of monolayer BN, MoS2, MoSe2, MoTe2, WS2, WSe2, and WTe2 reveal that some of these materials exhibit stronger piezoelectric coupling than traditionally employed bulk wurtzite structures. We find that the piezoelectric coefficients span more than 1 order of magnitude, and exhibit monotonic periodic trends. The discovery of this property in many two-dimensional materials enables active sensing, actuating, and new electronic components for nanoscale devices based on the familiar piezoelectric effect.

834 citations

Journal ArticleDOI
TL;DR: The idea of wireless power transfer (WPT) has been around since the inception of electricity and Nikola Tesla described the freedom to transfer energy between two points without the need for a physical connection to a power source as an?all-surpassing importance to man? as discussed by the authors.
Abstract: The idea of wireless power transfer (WPT) has been around since the inception of electricity. In the late 19th century, Nikola Tesla described the freedom to transfer energy between two points without the need for a physical connection to a power source as an ?all-surpassing importance to man? [1]. A truly wireless device, capable of being remotely powered, not only allows the obvious freedom of movement but also enables devices to be more compact by removing the necessity of a large battery. Applications could leverage this reduction in size and weight to increase the feasibility of concepts such as paper-thin, flexible displays [2], contact-lens-based augmented reality [3], and smart dust [4], among traditional point-to-point power transfer applications. While several methods of wireless power have been introduced since Tesla?s work, including near-field magnetic resonance and inductive coupling, laser-based optical power transmission, and far-field RF/microwave energy transmission, only RF/microwave and laser-based systems are truly long-range methods. While optical power transmission certainly has merit, its mechanisms are outside of the scope of this article and will not be discussed.

745 citations

Journal ArticleDOI
TL;DR: In this article, a 64-element dual-circularly-polarized spiral rectenna array is designed and characterized over a frequency range of 2-18 GHz with single-tone and multitone incident waves.
Abstract: This paper presents a study of reception and rectification of broad-band statistically time-varying low-power-density microwave radiation. The applications are in wireless powering of industrial sensors and recycling of ambient RF energy. A 64-element dual-circularly-polarized spiral rectenna array is designed and characterized over a frequency range of 2-18 GHz with single-tone and multitone incident waves. The integrated design of the antenna and rectifier, using a combination of full-wave electromagnetic field analysis and harmonic balance nonlinear circuit analysis, eliminates matching and filtering circuits, allowing for a compact element design. The rectified dc power and efficiency is characterized as a function of dc load and dc circuit topology, RF frequency, polarization, and incidence angle for power densities between 10/sup -5/-10/sup -1/ mW/cm/sup 2/. In addition, the increase in rectenna efficiency for multitone input waves is presented.

687 citations

Patent
16 Jul 2002
TL;DR: In this paper, the fabrication and growth of sub-microelectronic circuitry is described, and the arrangement of such articles to fabricate electronic, optoelectronic, or spintronic devices and components.
Abstract: The present invention relates generally to sub-microelectronic circuitry, and more particularly to nanometer-scale articles, including nanoscale wires which can be selectively doped at various locations and at various levels. In some cases, the articles may be single crystals. The nanoscale wires can be doped, for example, differentially along their length, or radially, and either in terms of identity of dopant, concentration of dopant, or both. This may be used to provide both n-type and p-type conductivity in a single item, or in different items in close proximity to each other, such as in a crossbar array. The fabrication and growth of such articles is described, and the arrangement of such articles to fabricate electronic, optoelectronic, or spintronic devices and components. For example, semiconductor materials can be doped to form n-type and p-type semiconductor regions for making a variety of devices such as field effect transistors, bipolar transistors, complementary inverters, tunnel diodes, light emitting diodes, sensors, and the like.

598 citations