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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Electronic properties of two-dimensional carbon systems

Mohammed, Faris Siedahmed 18 September 2012 (has links)
Properties of graphene-based nanoelectronic devices are found to be limited by disorder, e.g., vacancies, impurities and ripples on the surface. We investigate the speci c e ect of defects concentration as well as the structural modulation (ripples) on the electronic properties of layers of graphene-based electronic devices. We show the promise of a possible route for improvement of the current-voltage characteristics by incorporating nitrogen atoms in the defective graphene (which has limited device applications). In this work, we develop the tight-binding model of two-dimensional (2D) carbon and use the recursive Green's function method to study the e ect of defects concentration as well as periodic structural disorder (ripples) where it has already been studied using the Dirac Hamiltonian. The combined e ect of vacancies and ripples on the electronic transport of graphene devices was studied. The presence of vacancies results in quasi-localized states at the Fermi energy. This is also found to be common in the presence of ripples, but in that case they are Landau levels originating from the gauge eld induced by the ripples. In contrast, resonant states emerge when charged impurities are substituted. The density of these resonances was found to be tunable by controlling the ratio between the impurity-carbon coupling to impurity ons-site potential as well as the concentration. With regard to the mesoscopic phenomena, the system gains zero conductance due to the opening of an energy gap when the ripples as well as vacancies are present. In particular, the transport becomes di usive rather than ballistic in the case of ripples, which has already been found previously within the Dirac Hamiltonian approach. On the other hand, the impurity enhances the transport properties due to augmentation of the resonant states in the vicinity of the Fermi level. Moreover, the increase of the sample-lead coupling was found to broaden the levels and increase the current by over one order of magnitude. The study shows the possibility of tuning the electronic transport of 2D carbon systems by controlling the structural and topological defects, which can be extended toward the understanding of experimental observations such as enhanced transport properties in 2D graphitic carbon lms incorporated with nitrogen.
2

The physical structure and adsorptive properties of heat treated porous carbons / by D.R.G. Williams

Williams, Donald Reginald Glyndwr January 1964 (has links)
337 leaves : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1965) from the Dept. of Mining, Metallurgical and Chemical Engineering, University of Adelaide
3

The physical structure and adsorptive properties of heat treated porous carbons / by D.R.G. Williams

Williams, Donald Reginald Glyndwr January 1964 (has links)
337 leaves : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1965) from the Dept. of Mining, Metallurgical and Chemical Engineering, University of Adelaide
4

Carbon and nitrogen dynamics in agroforestry systems : temporal patterns of some important soil processes /

Nyberg, Gert, January 1900 (has links) (PDF)
Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2001. / Härtill 4 uppsatser.
5

The physical structure and adsorptive properties of heat treated porous carbons /

Williams, Donald Reginald Glyndwr. January 1964 (has links) (PDF)
Thesis (Ph.D. 1965) from the Dept. of Mining, Metallurgical and Chemical Engineering, University of Adelaide.
6

Carbon 13 in tree rings of a Wisconsin oak and its implications for changes in atmospheric CO₂

Berge, Arden J. January 1978 (has links)
Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 91-96).
7

Isotope shift in the atomic spectrum of carbon

Burnett, Clyde R., January 1951 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1951. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 41-42).
8

Certain forms of artificial carbon

Black, Richard Granger. January 1935 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1935. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
9

The absolute intensity of C₂ swan bands

Hagan, Lucy Gay. January 1963 (has links)
Thesis (Ph.D.)--University of California, Berkeley, 1963. / "UC-4 Chemistry" -t.p. "TID-4500 (19th Ed.)" -t.p. Includes bibliographical references (p. 109-114).
10

The oxidation of carbon by cuprous oxide-lead oxide-silica melts

Joshi, Ashok Purushottam January 1960 (has links)
An investigation of the relationship between the kinetics of the oxidation of spectroscopic grade graphite with the oxidising potential of cuprous oxide-lead oxide-silica melts was undertaken. The kinetics of the reaction were studied at two temperatures over a wide range of oxidising potentials. In all cases it was observed that the rate of oxidation was proportional to the equilibrium oxygen pressure of the system and the square of the activity of the oxygen ions. The variation of the rate constant with temperature indicated that O⁻⁻ are involved in the rate determining step. At a given temperature the rate constants for the simple PbO—SiO₂ and the complex Cu₂O—PbO—SiO₂ slags were found to be of the same order of magnitude, if O⁻⁻ were considered. Hence the rate expression could be written as [formula omitted] The activation energy of oxidation of graphite was determined over a wide range of PbO—SiO₂ composition, and found to have a value of 22±2 Kcal./mole. The activation energy for spectroscopic grade carbon was found to have a value of 22 Kcal./mole, indicating that the activation energy was independent of the nature of the carbon surface. The constant A was observed to have a value of 12 for the slags investigated. The theory of the ionic equilibrium in silicate melts devised by Toop and Samis was extended to calculate aO⁻⁻ and silica in multicomponent silicate slags. The present investigation appears to substantiate their theory. The results obtained in this study indicate that aO⁻⁻ in an unknown silicate melt might be determined by oxidising carbon in the melt and measuring the rate of oxidation. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

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