Showing papers by "Michael S. Fuhrer published in 2006"
01 Jan 2006
TL;DR: In this article, the resistance of single-wall carbon nanotubes measured in a four-point configuration with noninvasive voltage electrodes was investigated and the voltage drop was detected using multi-walled carbon-nanotubes whil the current was injected through nanofabricated Au electrodes.
Abstract: We have studied the resistance of single-wall carbon nanotubes measured in a four-point configuration with noninvasive voltage electrodes. The voltage drop is detected using multiwalled carbon nanotubes whil the current is injected through nanofabricated Au electrodes. Th resistance at room temperature is shown to be linear with th length as expected for a classical resistor. This changes at cryogenic temperature; the four-point resistance then depends on the transmission coefficients between the different electrodes and can even become negative due to quantum-interference effects, as expected from the Laudauer-Buttiker theory.
106 citations
TL;DR: In this paper, the 1∕f noise in individual semiconducting carbon nanotubes (s-CNT) in a field effect transistor configuration has been measured in ultrahigh vacuum and following exposure to air.
Abstract: The 1∕f noise in individual semiconducting carbon nanotubes (s-CNT) in a field effect transistor configuration has been measured in ultrahigh vacuum and following exposure to air. The amplitude of the normalized current spectral noise density is independent of source-drain current and inversely proportional to gate voltage, to channel length, and therefore to carrier number, indicating that the noise is due to mobility rather than number fluctuations. Hooge’s constant for s-CNT is found to be (9.3±0.4)×10−3 The magnitude of the 1∕f noise is substantially decreased by exposing the devices to air.
95 citations
TL;DR: In this article, the 1/f noise in individual semiconducting carbon nanotubes (s-CNT) in a field effect transistor configuration has been measured in ultra-high vacuum and following exposure to air.
Abstract: The 1/f noise in individual semiconducting carbon nanotubes (s-CNT) in a field effect transistor configuration has been measured in ultra-high vacuum and following exposure to air. The amplitude of the normalized current spectral noise density is independent of source-drain current, indicating the noise is due to mobility rather than number fluctuations. Hooge's constant for s-CNT is found to be 9.3 plus minus 0.4x10^-3. The magnitude of the 1/f noise is substantially degreased by exposing the devices to air.
79 citations
TL;DR: Electrical power >1 mW is dissipated in semiconducting single-walled carbon nanotube devices in a vacuum, and upon exposure to air, devices recover p-type behavior, with positive threshold and ohmic contacts.
Abstract: Electrical power >1 mW is dissipated in semiconducting single-walled carbon nanotube devices in a vacuum. After high-power treatment, devices exhibit lower on currents and intrinsic, ambipolar behavior with near-ideal thermionic emission from Schottky barriers of height one-half the band gap. Upon exposure to air, devices recover p-type behavior, with positive threshold and ohmic contacts. The air-exposed state cannot be explained by a change in contact work function but instead is due to doping of the nanotube.
72 citations
TL;DR: Conditions for the transfer printing of patterned carbon nanotube (CNT) films, along with a Au-gate, a poly methylmethacrylate (PMMA) dielectric layer and Au source-drain electrodes have been developed for the fabrication of thin-film transistors on a polyethylene terephthalate (PET) substrate as discussed by the authors.
Abstract: Conditions for the transfer printing of patterned carbon nanotube (CNT) films, along with a Au-gate, a poly methylmethacrylate (PMMA) dielectric layer and Au source-drain electrodes have been developed for the fabrication of thin-film transistors on a polyethylene terephthalate (PET) substrate. Chemical vapor deposition (CVD) grown CNTs were patterned using a photolithographic method. Transfer printing was used to fabricate devices having both top gate and bottom gate configurations. Replacement of the SiO 2 dielectric with PMMA correlates with a decreased hysteresis in the transconductance behavior. Encapsulation of the CNTs between the polymeric substrate and dielectric layer yields ambipolar behavior. Variations in device performance are also observed as a function of CNT film density and channel length, suggesting changing contributions of the metallic and semiconducting CNTs to the transport mechanism.
15 citations
TL;DR: In this paper, a Boltzrnann-equation model for charge transport in semiconducting single-walled carbon nanotubes (s-SWNTs) is developed with two adjustable parameters, the acoustic and optical phonon scattering lengths.
Abstract: A simple Boltzrnann-equation model for charge transport in semiconducting single-walled carbon nanotubes (s-SWNTs) is developed with two adjustable parameters, the acoustic and optical phonon scattering lengths. The model predicts velocity saturation rather than current saturation in s-SWNTs at high bias, in agreement with a recent experiment. At moderate densities, the model predicts currents in s-SWNTs exceeding 25 μA, the limiting current in long metallic single-walled carbon nanotubes.
8 citations
TL;DR: In this paper, the authors measured the resistance and frequency-dependent gate capacitance of carbon nanotube (CNT) thin films in ambient, vacuum, and under low-pressure (10E-6 torr) analyte environments.
Abstract: We measure the resistance and frequency-dependent gate capacitance of carbon nanotube (CNT) thin films in ambient, vacuum, and under low-pressure (10E-6 torr) analyte environments. We model the CNT film as an RC transmission line and show that changes in the measured capacitance as a function of gate bias and analyte pressure are consistent with changes in the transmission line impedance due to changes in the CNT film resistivity alone; the electrostatic gate capacitance of the CNT film does not depend on gate voltage or chemical analyte adsorption. However, the CNT film resistance is enormously sensitive to low pressure analyte exposure.
TL;DR: In this paper, electron transport measurements of single-wall carbon nanotubes in a four-terminal configuration with noninvasive voltage electrodes were carried out at high temperature so that the fourterminal resistance directly gave the intrinsic resistance.
Abstract: We report on electron transport measurements of single-wall carbon nanotubes in a four-terminal configuration with noninvasive voltage electrodes. The voltage drop is detected using multiwalled carbon nanotubes while the current is injected through nanofabricated Au electrodes. Measurements are carried at high temperature so that the four-terminal resistance directly gives the intrinsic resistance. The resistance is shown to result from weak disorder and from quantum interference effect corrections. In addition, we present Coulomb blockade measurements. The length of the quantum dot that is determined from the level spacing equals the separation between the Au electrodes.
31 Jul 2006
TL;DR: In this article, the authors synthesize a number of experimental and theoretical approaches to understand the relationship between morphological fluctuations, the electrical response and the reliability (failure) of metallic nanostructures.
Abstract: The goal of the research supported by DOE-FG02-01ER45939 was to synthesize a number of experimental and theoretical approaches to understand the relationship between morphological fluctuations, the electrical response and the reliability (failure) of metallic nanostructures. The primary focus of our work was the study of metallic nanowires which we regard as prototypical of nanoscale interconnects. Our research plan has been to link together these materials properties and behaviors by understanding the phenomenon of, and the effects of electromigration at nanometer length scales. The thrust of our research has been founded on the concept that, for nanostructures where the surface-to-volume ratio is necessarily high, surface diffusion is the dominant mass transport mechanism that governs the fluctuations, electrical properties and failure modes of nanostructures. Our approach has been to develop experimental methods that permit the direct imaging of the electromagnetic distributions within nanostructures, their structural fluctuations and their electrical response. This experimental research is complemented by a parallel theoretical and computational program that describes the temporal evolution of nanostructures in response to current flow.