DSpace Coleção:
http://www.repositorio.ufc.br/handle/riufc/212
2019-06-18T16:38:21ZInstrumentação e montagem de um sistema de SNOM para medidas de nanoestruturas individuais
http://www.repositorio.ufc.br/handle/riufc/42405
Título: Instrumentação e montagem de um sistema de SNOM para medidas de nanoestruturas individuais
Autor(es): Moura, Thiago Alves de
Abstract: The Raman Spectroscopy is a well stablished technique to study the chemical and structural properties of a variety of nanomaterials. However, its full potentiality on nanoscale is limited by the diffraction limit and the low intensity of Raman signal, for the most of single nanoobjects or molecules. The Tip Enhanced Raman Spectroscopy (TERS) appears as a useful technique to overcoming these barriers, thus allowing the applicability of Raman spectroscopy to analyse nanostructures. In this work, we describe the functional principles of TERS and the implementation of experimental apparatus needed to its realization, which include setting the AFM, optics and tip fabrication. The system was successfully tested by measuring single linear carbon chains. Simultaneously, carbon nanotubes containing linear carbon chain are studied.2017-01-01T00:00:00ZInfluência do sistema Aharonov-Bohm-Coulomb na dinâmica do oscilador de Dirac e de uma partícula com massa efetiva dependente da posição
http://www.repositorio.ufc.br/handle/riufc/41726
Título: Influência do sistema Aharonov-Bohm-Coulomb na dinâmica do oscilador de Dirac e de uma partícula com massa efetiva dependente da posição
Autor(es): Oliveira, Rubens Raimundo de Sousa
Abstract: In this dissertation, we study the influence of the Aharonov-Bohm-Coulomb (ABC) system on the relativistic and nonrelativistic quantum dynamics of the Dirac oscillator (DO) and of a Dirac particle with position-dependent effective mass (PDEM). To obtain the bound-state solutions of these two problems, we use the projection operators left-handed and right-handed. With respect to the results of the first problem, we verified that Dirac spinor is written in terms of the biconfluent Heun functions and the relativistic energy spectrum depends on the parameters Z and Φ which characterize the ABC system and of the cyclotron frequency ωc characterizes a uniform magnetic field. We observed that Z has the function of increase the values of this spectrum, while ωc has the function of decrease. In particular, we note a peculiar quantum effect: the angular frequencies of the OD are quantized in terms of quantum numbers. In addition to these frequencies being real and positive quantities, are linearly proportional to ωc and increase quadratically with Z and the energies of the system. By consequence of this unusual result, the energies of the ground state are greater of the that the of the first excited state. When we analyze the nonrelativistic limit of this first problem, we obtain the equation of the quantum harmonic oscillator (QHO) with a strong spin-orbit coupling in the presence of a uniform magnetic field and under the influence of the ABC system. Unlike of the DO, the frequencies of the QHO increase linearly with the energies. Now, with respect to the results of the second problem, we verify that the Dirac spinor is written in terms of the generalized Laguerre polynomials and the relativistic energy spectrum depends of Z, ω and of the parameter k that characterizes the PDEM. We observed that ω and k have the function of increase the values of this spectrum, while Z has the function of decrease. In special, when we take the constant mass limit (κ → 0), the results of the relativistic ABC system are recovered. However, we verified that even in the absence of the ABC system (Φ = Z = 0), the energy spectrum of the free particle with MEDP still remains quantized. On the other hand, when we analyze the nonrelativistic limit of our last problem, we obtain the Schrödinger equation (SE) for a particle with PDEM under the influence of the ABC system, where we verify that the energy spectrum of such an equation is reduced to the spectrum of the nonrelativistic ABC system in the limit (Φ = Z = 0), while for Φ = Z = 0, reduces to the spectrum of the free particle with MEDP.2019-01-01T00:00:00ZFuncionalização química de nanofitas de fosforeno de bordas reconstruídas – propriedades estruturais e eletrônicas
http://www.repositorio.ufc.br/handle/riufc/41495
Título: Funcionalização química de nanofitas de fosforeno de bordas reconstruídas – propriedades estruturais e eletrônicas
Autor(es): Castro, Giselle dos Santos
Abstract: Phosphorene is a direct gap semiconductor, of approximately 2.0 eV, with high electronic mobility. Its structural and electronic properties can be modified when it is “cut” and adapted into derived nanostructures, as nanoribbons. The physical properties of phosphorene nanoribbons are dependent on their crystalline form and edge configuration.
In this work, we use the first principles calculation based on density functional theory to study the effects of phosphorene nanoribbons surface functionalization of reconstructed edges (self passivated) on the structural and electronic properties of the system upon adsorption. Different chemical elements, such as Li, O, F and Cl, in concentrations of 1/32, 1/16 and 1/8 were applied.2019-01-01T00:00:00ZPropriedades termodinâmicas de buracos negros com métricas que violam a simetria de Lorentz
http://www.repositorio.ufc.br/handle/riufc/41074
Título: Propriedades termodinâmicas de buracos negros com métricas que violam a simetria de Lorentz
Autor(es): Gomes, Débora Aguiar
Abstract: Hawking radiation has provided a new horizon in the study of black holes. Classically, black holes do not emit radiation, only absorb it. However, when it comes to a quantum mechanical approach, it is possible to show that black holes do emit radiation. Many methods have been developed to evaluate black hole thermodynamical properties. Among them, we can highlight a semi-classical method, known as quantum tunneling, which has been applied to many gravitational models with satisfactory results. In the Hawking radiation context, the Lorentz symmetry breaking (LSB) can provide interesting contributions in the Planck energy scale. In the literature, we find calculations of the thermodynamical properties of LSB Schwarzschild-like solutions, using the surface gravity. In this work, we present the first results obtained via quantum tunneling method for Schwarzschild-like models in which the Lorentz symmetry does not hold.2018-01-01T00:00:00Z