Download or read book Conductance Probe Microscopy Investigation on the Local Electronic Properties of Single Walled Carbon Nanotube Systems written by Peter Niraj Nirmalraj and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electronic Properties of Electrochemically Modified Single walled Carbon Nanotubes written by Vaikunth Rawloo Khalap and published by . This book was released on 2010 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract The functionalization of carbon nanotubes is a research topic with applications in a wide range of fields, from carbon nanotube based electronic sensor development to improving the electrical properties of carbon nanotubes for use as interconnects between larger circuit elements. This dissertation examines the impact of point-functionalizations on the conductance of single carbon nanotube devices. Due to their reduced size and dimensionality, carbon nanotubes act as an ideal system to electronically probe the characteristics of single functionalizations. Point-functionalizations can easily be introduced into carbon nanotube sidewalls using an electrochemical technique, which allows the experimenter to have total control over the rate of functionalization. The presence of point-functionalizations dominates the electronic properties of carbon nanotube devices. In this work, these sites are shown to be more chemically reactive, allowing metal nanoparticles to be selectively nucleated and grown on functionalized sites. Additionally, the presence of a single functionalized site coupled to a single palladium nanoparticle can be used to make a single carbon nanotube hydrogen sensor, with sensitivity down to the part per million level. Finally, cyclic voltammetry experiments show that point-functionalizations have much faster electron transfer rates than pristine carbon nanotubes alone.

Download or read book Electronic Properties of Carbon Nanotubes written by Jose Mauricio Marulanda and published by BoD – Books on Demand. This book was released on 2011-07-27 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes (CNTs), discovered in 1991, have been a subject of intensive research for a wide range of applications. These one-dimensional (1D) graphene sheets rolled into a tubular form have been the target of many researchers around the world. This book concentrates on the semiconductor physics of carbon nanotubes, it brings unique insight into the phenomena encountered in the electronic structure when operating with carbon nanotubes. This book also presents to reader useful information on the fabrication and applications of these outstanding materials. The main objective of this book is to give in-depth understanding of the physics and electronic structure of carbon nanotubes. Readers of this book should have a strong background on physical electronics and semiconductor device physics. This book first discusses fabrication techniques followed by an analysis on the physical properties of carbon nanotubes, including density of states and electronic structures. Ultimately, the book pursues a significant amount of work in the industry applications of carbon nanotubes.

Download or read book Electrical and Mechanical Investigations of Carbon Nanotubes written by Thomas Wray Tombler and published by . This book was released on 2002 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Carbon Nanotubes written by Stephanie Reich and published by John Wiley & Sons. This book was released on 2004-03-12 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanoröhrchen aus Kohlenstoff werden hervorragende Eigenschaften nachgesagt: sie sind chemisch sehr stabil, mechanisch sehr fest und elektrisch leitend. Aufgrund dieses Charakters eröffnen sich Perspektiven für verschiedene Anwendungen: als Nanotransistoren in Schaltkreisen, als Wasserstoff-Speicher für Brennstoffzellen, als künstliche Muskeln oder als Zusatz zur Verstärkung von Verbundwerkstoffen. Vor allem in der Elektronik werden die fadenförmigen Makromolekülen aus Kohlenstoff eines Tages das Silizium verdrängen. Das vorliegende Buch ist eine Einführung in die Konzepte zur Behandlung und Untersuchung von Carbon Nanotubes für eine breite wissenschaftliche Leserschaft. Jedes Kapitel besteht aus einer edukativen Hinführung auf die Problematik sowie aus nachhaltigen Lösungskonzepten. Zum ersten Mal werden ab initio Rechnungen zur physikalischen Beschreibung von CNT vorgestellt und Ergebnisse aus neuen experimentellen Untersuchungsmethoden (STM, Raman) präsentiert.

Download or read book Carbon Nanotube Defects and Carbon Nanotube Composites written by Deng Pan and published by . This book was released on 2014 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: A single-walled carbon nanotube (SWCNT) is a one-dimensional (1D) conductor that has been proposed as an ideal element for novel, nanoscale electronics. This dissertation studies the properties of individual SWCNTs in the near-pristine limit where the SWCNT conductor contains one or more defects. The presence of defects significantly modifies the electronic and chemical properties of a SWCNT, with positive and negative impacts on different potential applications. This dissertation completed three different types of experiments to explore these modified properties. In the first section, SWCNTs with defects were studied during high temperature annealing. Annealing rearranged and diminished the scattering from defects, even to a point where pristine SWCNT conductances were recovered. In the limit of single defects on single SWCNTs, the annealing of one defect was resolved in real time by using electrical conductance as the probe. The work proved that conductance in 1D is sufficiently sensitive to see the annealing of one defect. The resistance associated with single SWCNT defect was also studied as a function of bias and temperature at low temperature. A singe point defect surrounded on either side by quasi-ballistic, semi-metallic SWCNT was a nearly ideal system for understanding the influence of functional groups on 1D conductors and comparing experiment to theory. Here, transport and local Kelvin Probe Force Microscopy (KPFM) independently demonstrated high-resistance depletion regions over 2.0 micron wide surrounding a point defect in a SWCNT. A defect assisted tunneling through this depletion region via a modified, 1D version of Poole-Frenkel conduction. Given the breadth of theory dedicated to the possible effects of disorder in 1D systems, it was surprising to find that a Poole-Frenkel model could successfully describe defect scattering in SWCNTs. Finally, the third experiment investigated SWCNTs that had been non-covalently modified with a thin coating of Cu. Bulk CNT/Cu composites have been reported to have surprisingly high conductance and ampacity. Consequently, CNT/Cu composites are a novel conductor with many potential applications. Here, individual SWCNTs were coated with Cu by electrodepotion for electrical studies. Due to SWCNT's hydrophobic and inert surface, achieving conformal Cu coatings was very difficult, but successful results were obtained using both aqueous and non-aqueous Cu electrolytes. The thinnest conformal Cu coatings (40nm) were obtained from electrodeposition in non-aqueous Cu electrolyte. Electrical measurement of Cu-coated SWCNTs revealed a similar temperature dependent to the bulk composite, indicating that the SWCNT plays an essential role in the composite conductance's temperature dependence. However, unlike the preliminary reports, Cu films at these thicknesses could only achieve a fraction of the conductivity of bulk Cu. Therefore, the research was unable to fully test the mechanisms of the improvements reported for bulk CNT/Cu composites.

Download or read book Electronic Properties of Single walled Carbon Nanotubes written by Teri Wang Odom and published by . This book was released on 2000 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electronic Characterization of Individual Single Walled Carbon Nanotubes written by Chi-Yan Wong and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Electronic Characterization of Individual Single-walled Carbon Nanotubes" by Chi-yan, Wong, 王志仁, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled ELECTRONIC CHARACTERIZATION OF INDIVIDUAL SINGLE-WALLED CARBON NANOTUBES Submitted by Wong Chi Yan for the Degree of Master of Philosophy at The University of Hong Kong in September 2007 The outstanding properties of carbon nanotubes (CNTs) have attracted con- siderable research effort in the last decade. CNTs are quasi-one-dimensional materials which can be used to study fundamental quantum effects of one- dimensional systems. TherehasbeenagreatdealofinterestspecificallyinsemiconductingCNTs, which have shown to be promising candidates as the building blocks for the next-generation electronic applications. Carbon nanotube electronic devices have the potential to replace conventional silicon-based counterparts. How- ever, there are still obstacles that remain with regard to the scientific study or application oriented researches. For example, the growth orientation and the band gaps of individual CNTs are difficult to control. In addition, pronounced low-frequency current fluctuation, 1/f noise, exists. The measured noise levelisevencomparabletothesignallevelundersomecircumstances, therebylimit- ing the application of CNTs in low-signal electronics and the overall reliability of CNT based devices. In this thesis, single-walled CNTs (SWNTs) were chosen as a studying modelduetotheirsimplicityinnature. DifferentmethodsofindividualSWNT fieldeffecttransistor(FET)fabricationmethodswerecompared. Themethods included: (I) Directed growth of ultra long SWNTs on a wafer by CVD using ethanol, and (II) Dispersing the SWNTs fabricated by ordinary CVD, on the wafer with organic solvents. The noise behavior for both fabrication methods were characterized by DAQ and lock-in noise measurement methods. Thereafter, thebasicI-V measurementsoffabricatedSWNTFETdevices were also performed. The hysteresis effect and its time dependent measure- ments in FETs were illustrated. The measurements results suggested that the hysteresis effect in nanotube devices was attributed to the charge traps in the oxide layer of FETs. Finally, the 1/f noise of SWNT FETs was studied. It was shown that the 1/f noise arose from the carrier number fluctuations rather than mobility fluctuations, as a superposition of Lorentzian fluctuation spectra. The corre- -2 sponding Hooge constant was found to be gate dependent and about 10 in thelinearregime. Bycomparingwiththereportedsimulationresultofrandom telegraphsignal(RTS)noiseamplitudeinsubthresholdregime, itwasproposed that such Lorentzian fluctuation spectra were due to the RTS noise, arising from the gate potential fluctuations in the CNT, and the charge exchange be- tween CNT and oxide layer. These potential fluctuations were attributed to trapped charges in the oxide nearby which changed the number of carriers in the CNTs. DOI: 10.5353/th_b3955704 Subjects: Nanotubes Nanostructured materials - Electric properties Transistors

Download or read book Electronic Properties of Carbon Nanotubes written by Leroy Sidney and published by . This book was released on 2016-04 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes (CNTs) are tubular cylinders of carbon atoms that have extraordinary mechanical, electrical, thermal, optical and chemical properties. CNTs typically have diameters ranging from 1 nanometer (nm) up to 50 nma nanometer is one thousand millionth of a meter. Typical CNT lengths are several micronsseveral thousand nanometers long; by contrast, Nanocomp's produced fibers are measured in millimetersthousands of times longer than all other commercially produced CNTs. They take the form of cylindrical carbon molecules and have novel properties that make them potentially useful in a wide variety of applications in nanotechnology, electronics, optics and other fields of materials science. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. In the powdery format offered by all CNT producers (but for NTI), applications are limited to the properties possible by this form factore.g. additive active ingredients in semiconductors, liquid crystal displays (LCDs), sensors, and other uses in which these powders add some level of functional performance. Due to its fiber length and its form factors, NTI delivers strength and conductivity unlike any other commercial CNT producer, and so can address a much broader array of applications for which its material rivals copper and aluminum in conductivity, and steel, aluminum, carbon fibers and glass composites where strength and lightweight matter. Carbon nanotubes have been a subject of exhaustive research for a wide range of applications. The purpose of this book entitled Properties of Carbon Nanotubes is to give in-depth understanding of the physics and electronic structure of carbon nanotubes. This book discusses fabrication techniques followed by an analysis on the physical properties of carbon nanotubes, including density of states and electronic structures. Eventually, the book follows a significant amount of work in the industry applications of carbon nanotubes.

Download or read book The Effects of Local Chemistry on the Growth and Electronic Properties of Carbon Nanotubes written by Jason M. Simmons and published by . This book was released on 2006 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of Carbon Nanotube Properties and Applications at Microwave and THz Frequencies written by and published by . This book was released on 2010 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents research on synthesis, high-power microwave post-synthetic purification and high frequency characterization of Carbon Nanotubes (CNT). First, CNTs are synthesized using a Chemical Vapor Deposition system. The impact of substrate and methane flow rate on CNT growth is studied using Scanning Electron Microscopy, Transmission Electron Microscopy and Raman microscopy. Second, the microwave irradiation effects on purified HiPCO and CoMoCat Single-Walled CNT thin films are investigated. The measured drastic THz power transmission increase (>10 times) indicates a significant metallic content reduction after the irradiation. The Raman spectra also confirm the metallic-to-semiconducting ratio of Raman-active CNTs decreases by up to 33.3%. The observed microwave-induced effects may potentially lead to a convenient scheme for CNT demetalization. Third, Multi-Walled CNT papers are characterized from 8 to 50 GHz by rectangular waveguide measurements using a vector network analyzer. A rigorous algorithm is developed to extract the samples' effective complex permittivity and permeability from the measured S-parameters. Unlike other reported work, this method does not impose the unity permeability assumption. The algorithm is verified by finite-element simulations and the uncertainties for the characterization method are analyzed. The effective medium theory is then applied to obtain the intrinsic CNT properties. Furthermore, Terahertz Time-Domain Spectroscopy is used to characterize the samples from 50 to 370 GHz. Both transmission and reflection experiments are performed to simultaneously extract the permittivity and permeability. The extracted permittivity is fitted with a Drude-Lorentz model from 8 to 370 GHz. Finally, individual CNT characterizations at microwave frequency are studied. The impacts from impedance mismatching and parasitics on measurement sensitivity are systematically studied, revealing that the parasitic effect is possibly dominant above 10 GHz. A tapered coplanar waveguide test fixture is designed using Advanced Design System (ADS) to improve the impedance mismatching and minimize the test fixture parasitics, therefore optimize the measurement sensitivity. A de-embedding procedure to obtain the CNT's intrinsic electrical properties is presented and demonstrated with ADS simulations. In addition, the test fixture fabrication process is discussed, which is an ongoing research work. At the end, the conclusions of this dissertation are drawn and possible future works are discussed.

Download or read book Optical Absorption and Electronic Properties of Individual Carbon Nanotubes written by Jean-Christophe Blancon and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, we report on the experimental investigation of the optical properties of single- and double-wall carbon nanotubes. Despite numerous studies performed using photoluminescence or Raman and Rayleigh scattering, knowledge of their optical response is still partial. In particular direct quantitative measurement of their absorption cross-section has not been achieved yet. Using spatial modulation spectroscopy we have determined, over a broad optical spectral range, the spectrum and amplitude of the absorption cross-section of identified individual single- and double-wall carbon nanotubes. These quantitative measurements permit the determination of the oscillator strength of the different excitonic resonances. Furthermore, investigation of the same nanotube, either a single-wall or double-wall nanotube, freestanding or deposited on a substrate shows large broadening with increase of oscillator strength of the excitonic resonances, as well as stark weakening of polarization dependent antenna effects, due to nanotube-substrate interaction. Similar study on nanotube bundles and double-wall nanotubes demonstrate the importance of inter-tube and inter-wall exciton coupling effects which seem to be of different nature in these two types of sample. The second part of this thesis studies electrical transport in carbon nanotube bundles under high pressure condition and low temperature. The behavior of nanotubebased field-effect transistors has been investigated, in the classical and Coulomb blockade regime, under gas-pressure up to 0.9 GPa. Overall, this dissertation communicates on the quantitative analysis of the absorption and electronic properties of carbon nanotubes and how they are influenced by various environmental effects such as dielectric screening, stress induced strain, hydrostatic pressure, or chemical doping. The novelty of this work is to address these issues at the single nanotube level.

Download or read book Scanning Photocurrent Microscopy Study of Photovoltaic and Thermoelectric Effects in Individual Single walled Carbon Nanotubes written by Tristan DeBorde and published by . This book was released on 2014 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon Nanotubes are a unique family of nanostructures that have shown remarkable promise for mechanical, electrical, and optical applications. Fundamentally similar to the earlier discovered Buckminsterfullerene (C60), carbon nanotubes are hollow cylinders formed from a single sheet of carbon atoms. The research presented in this dissertation investigates several carbon nanotube properties, with an emphasis on the interactions between light and electrons within the nanotube. Better understanding of these optoelectronic properties is of great interest for future advancement in solar energy conversion. Carbon nanotubes are a quintessential material for researchers studying nanoscience. Small changes in nanotube structure can lead to striking differences in electrical and optical properties. In addition to this rich variety of properties, nanotubes can be concentrically inset within one another resulting in single-walled, double-walled, and multi-walled versions. Single-walled carbon nanotubes are desirable for optoelectronic study as complicated interactions between shells are avoided; which, while an interesting topic, is beyond the scope of this work. In the past, determination of carbon nanotube wall number was achieved via transmission electron microscopy, a technique requiring difficult sample preparation, making it impractical for most working devices. This thesis presents an alternative technique based on the compressibility of nanotube sidewalls as measured by atomic force microscopy. This technique is readily applicable to common device designs and can distinguish single and double-walled carbon nanotubes. This technique has been applied to characterizing the output of our growth process, resulting in recipes that highly favor single-walled growth. The optical properties of single-walled carbon nanotubes have been studied intensely. Each single-walled nanotube has an optical fingerprint based on its unique atomic structure. Specific single-walled nanotube structures can be selected for a wide range of optical applications. Again, however, most techniques previously used to study these optical properties are not easily transferable to common device designs. In this research, the measurement of nanotube fingerprints is achieved by optoelectronic means through the use of a newly constructed scanning photocurrent microscope. This instrument measures changes in electrical transport as the device is locally illuminated by a spectrally-tunable light source, making it a versatile tool for studying nanostructures implemented in a variety device designs. Early work on nanotube optoelectronic properties attributed photocurrent generation to a photovoltaic mechanism. This thesis, however, shows that strong photothermoelectric effects can also be present in nanotube optoelectronic devices. Light absorbed by a nanostructure can locally raise the temperature, resulting in thermoelectric currents. If a carbon nanotube is being employed as the absorbing element of a solar cell, it is possible for thermoelectric currents to reduce or enhance the efficiency of energy conversion. The last portion of this work investigates the nature of optically generated thermoelectric effects in carbon nanotubes. With a better understanding of these thermoelectric effects, future nanostructure solar cell design can efficiently utilize thermoelectric currents.

Download or read book Investigations Into the Optical Properties of Individual Air suspended Single walled Carbon Nanotubes written by Mark William Brennan Wilson and published by . This book was released on 2008 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: Single-walled carbon nanotubes are naturally-forming nanostructures that have attracted considerable recent research interest due to their unique opto-electronic properties and comparative ease of fabrication. Two-thirds of nanotube species are semiconductors due to symmetry conditions imposed by their pseudo-one-dimensional tubular structure, and exhibit band-gap photoluminescence when isolated from their environment. Despite their elegant structural simplicity, fundamental properties of carbon nanotubes, such as their intrinsic quantum efficiency, non-linear excitonic recombination mechanisms, and the role of environmental effects, continue to be disputed in the literature. The design of an apparatus capable of observing nanotube photoluminescence is presented, along with conclusive proof of the observation of a single (9,8)-chirality nanotube in the form of spectral, spatial, and polarization-dependent measurements. The dependance of the excitation and emission spectra of a single nanotube on the excitation intensity is explored and the emission spectra found to be described by a Gaussian peak function, in contrast to previously-reported results. The unexpected ability to cause redshifts in the emission spectrum via the ambient humidity is discovered, which has consequences on experimental best practices. Photoluminescence quantum efficiencies are measured to be 4"2% and 13"6% for two different nanotubes. This is at the high end of the range for comparable literature results, and supports the validity of a recent literature value for the effective atomic absorption coefficient for carbon, AC=1.6 x 10^- 3nm^2, which is ten times greater than previous literature values. Pulsed power dependence studies show that the PL emission undergoes 'hard' saturation at an excitation intensity of 0.5 x 10^12photons/pulse/cm2, which is at least 100 times lower than previous reports and provides insight into non-linear decay dynamics. A novel theoretical model is developed to explain this saturation process, which yields an absorption co-efficient of AC=1.2"0.3 x 10^ - 3nm^2 as a fit parameter. Time-resolved photoluminescence dynamics are explored using femtosecond excitation correlation spectroscopy. Results suggest that the one-body decay processes are bi-exponential, with time constants of 31"4ps and 313"61ps, but also highlight the limitations of this technique in observing the expected very rapid (~1 ps) two-body Auger recombination process.

Download or read book Investigating the Electronic Properties of Carbon Nanotubes Using a Scanning Tunnlling Microscope written by Michael Twerdochlib and published by . This book was released on 2010 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Quantitative Optical Imaging of Single walled Carbon Nanotubes written by Lihong Huang Herman and published by . This book was released on 2013 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development and application of optical imaging tools and probing techniques have been the subject of exciting research. These tools and techniques allow for non-invasive, simple sample preparation and relatively fast measurement of electronic and optical properties. They also provided crucial information on optoelectronic device application and development. As the field of nanostructure research emerged, they were modified and employed to understand various properties of these structures at the diffraction limit of light. Carbon nanotubes, up to hundreds of micrometers long and several nanometers thin, are perfect for testing and demonstrating newly-developed optical measurement platforms for individual nanostructures, due to their heterogeneous nature. By employing two quantitative imaging techniques, wide-field on-chip Rayleigh scattering spectroscopy and spatial modulation confocal absorption microscopy, we investigate the optical properties of single-walled carbon nanotubes. These techniques allow us to obtain the Rayleigh scattering intensity, absolute absorption cross section, spatial resolution, and spectral information of single-walled carbon nanotubes. By probing the optical resonance of hundreds of single-walled carbon nanotubes in a single measurement, the first technique utilizes Rayleigh scattering mechanism to obtain the chirality of carbon nanotubes. The second technique, by using high numerical aperture oil immersion objective lenses, we measure the absolute absorption cross section of a singlewalled carbon nanotube. Combining all the quantitative values obtained from these techniques, we observe various interesting and recently discovered physical behaviors, such as long range optical coupling and universal optical conductivity on resonance, and demonstrate the possibility of accurate quantitative absorption measurement for individual structures at nanometer scale.

Download or read book Synthesis Structure and Electronic Properties of Single walled Carbon Nanotubes written by Leslie Brian Fleming and published by . This book was released on 2003 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: