Navegando por Autor "NASCIMENTO, Clerisson Monte do"

Agora exibindo 1 - 4 de 4

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Análise de estruturas planares em THz baseadas em grafeno
(Universidade Federal do Pará, 2016-01-28) NASCIMENTO, Clerisson Monte do; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
In this work we analyse the properties of scattering of electromagnetic waves in graphene surfaces and the planar plasmonic based devices made of the same material, both in THz frequency region. The work is presented in form of four scientific papers. In the first one a numerical analysis of the plasmonic waves propagation in graphene elements is performed. The influence of geometrical configuration, chemical potential variation, angle of incidence and polarizations is analysed. That results give us the information to project two devices (the second and third) based on frequency selective surfaces (FSS) on THz range and that are composed only by graphene elements and dielectric substrates without the insertions of different metals. The first device consists in a THz electromagnetic filter made by an planar array of graphene ring-shaped elements placed in both sides of a dielectric substrate. The second device presents new multifunctional graphene device that can operate either as an electromagnetic, dynamically controlled, filter or as an eletromagnectic switch. Both devices operates based on Fano resonance effect. The fourth paper presents a new method of analysis of periodic planar structure, based on group theory approach. This method takes account the transversal and longitudinal components of induced current in the structure. By using this, one can obtain more information about the device properties than by using exitenting methods, which uses only longitudinal components of the induced currents. As application, we suggest an analyse a periodic array of graphene elements.
Acesso aberto (Open Access)
Analysis of electronic structure of boron nitride nanotubes with different positions of intrinsic impurities
(2014-12) GOMES, Fernando Antonio Pinheiro; DMITRIEV, Victor Alexandrovich; NASCIMENTO, Clerisson Monte do
The pristine boron nitride nanotubes have a large direct band gap around 5 eV. This band gap can be engineered by doping. We investigate electronic structure of the doped hexagonal boron nitride (5,5) nanotubes using the linearized augmented cylindrical wave method. In particular, this work focuses on systematical study of the band gap and the density of states around the Fermi-level when the nanotubes are doped by intrinsic impurities of two substitutional boron atoms in a super cell and a comparative analysis of the relative stability of three structures studied here. This corresponds to 3.3% of impurity concentration. We calculate 29 configurations of the nanotubes with different positions of the intrinsic impurities in the nanotube. The band gap and density of states around the Fermi level show strong dependence on the relative positions of the impurity atoms. The two defect sub bands called D∏(B) appear in the band gap of the pristine nanotube. The doped nanotubes possess p-type semiconductor properties with the band gap of 1.3-1.9 eV.
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Nanoelectronic Devices Based on Carbon Nanotubes
(Universidade Federal do Pará, 2015-03) DMITRIEV, Victor Alexandrovich; GOMES, Fernando Antonio Pinheiro; NASCIMENTO, Clerisson Monte do
Carbon nanotubes are possible building blocks in the development of new generation of electronic devices. The carbon nanotubes allow one fabrication of devices using nanometric scales. They can be used in projects of a wide range of electronic and optoelectronic components such as diodes, transistors and interconnection elements, among others. This paper presents the state-of-the-art of this area, emphasizing the influence of quantum effects on the characteristics of such components.
Acesso aberto (Open Access)
Transporte eletrônico em nanofitas de grafeno sob a influência de fatores externos, via primeiros princípios
(Universidade Federal do Pará, 2012) NASCIMENTO, Clerisson Monte do; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
Graphene was the first two-dimensional structure obtained experimentally. Its crystalline lattice is a hexagonal network with a unique atom thick, known as "Honeycomb". Cuts in graphene sheets, which favour a certain direction, generate the so-called graphene nanoribbons. Although graphene behaves like a metal, without considering spin polarization or any type of doping, nanoribbons can present metallic, semi-metallic or semiconductor behaviour, depending on the direction of the cutting and/or on the width of the ribbon. In the case of the semiconductor nanoribbons, the width of the band gap can depends directly on the width of the nanoribbon. Generally, the treatment is predominantly computational, for example, the DFT (Density Functional Theory), in order to obtain characteristics such as dispersion curves for nanoribbons, or the treatment can also be experimental. In this work, we first present the diagrams of energy band and the curves of density of states for semiconductor graphene nanoribbons of different widths and in the absence of external influences. Methods of first principles were used to obtain these curves and the method of Green functions of non-equilibrium was used to obtain the electronic transport. Subsequently, we investigated the influence of the hydrogenation, of the temperature and of the mechanical stress over the system, in order to analyse the behaviour of the electronic transport with and without external influences. It is noteworthy that the graphene nanoribbons present real possibilities of application in nanoelectronic devices, such as nanodiodos and nanotransistores. For this reason, it is important to understand how external factors affect the properties of such materials. So, it is expected that the properties of electronic devices are also influenced in the same way as the properties of the nanoribbons are influenced too.