Toward Plasmonic UC-PBG Structures based SWCNTs for Optoelectronics Applications

In this paper, the possibility of performing UC-PBG layers that is constructed from a forest of Single Wall Carbon Nanotubes (SWCNT) are aligned vertically on a thin flat film of quartz is studied. Such study is concerned in plasmonic optoelectronic applications in the visible regime. The study is conducted to the numerical simulations based Finite Element Method (FEM), then, compared with measurements. Remarkable benchmarks are found in the performance of the proposed UC-PBG which can be summarized as: 1excellent ability of focusing the light over a wide range of the visible bands, 2low effective losses, 3a miniaturized size of the numerical a preacher, 4no spherical apparition due to the flat geometry. It is found the proposed UC-PBG shows an effective refractive index varies from 10 to 20 in Lorentz-Drude manner. The maximum induced power of the proposed UC-PBG is found to be around 450 nm. Nevertheless, the size of the proposed UC-PBG layer is 200nm×200nm. Finally, the obtained results are compared to another numerical analysis based on Finite Integral Technique (FIT). Excellent agreements are found between the two invoked numerical methods.


Introduction
In differ from small carbon fibers of conductive properties that are treated by traditional manufacturing techniques with limited availability and expensive costs [1].Moreover, these difficulties are engaged to high dispersion degrees that continue to the carbon nanotube composites manufacturing challenges [2].Currently, most conductive carbon nanotube solutions are performed in laboratories using chemical evaporation methods [3][4][5][6].The solutions and curing agents properly vary with different polymer matrices [7].Generally, this procedure includes dissolving polymers to form a solution mixed with carbon nanotubes diluted by the aid of ultra-sonication to create casting films or solid parts then subjected to a curing process [8].However, most of these techniques reduce the real advancements in the electromagnetic properties of the SWCNTs when they are treated as bulk films not as ballistic conductors [1].Therefore, to achieve more uniform SWCNTs dispersion in array forms and get the advantage of their ballistic properties at the individual ones, vertically aligned forests are subjected to the research [9][10][11][12].In [9], electron beam evaporation on a thermal oxide layer of silicon substrate is used to grow the SWCNTs vertically with the aid of chemical vapor deposition plasma system.A controlled atomic diffusion-induced catalyst evolution on an aluminum thin-film substrate was introduced in [10] to grow vertically aligned carbon nanotube arrays by a conventional low-pressure thermal chemical vapor deposition.Vertical SWCNT arrays of a uniform distribution were grown by combining chemical vapor deposition and block copolymer lithography [11].Synthesizing vertically aligned SWCNT arrays using a decoupled method that facilitates control of the growth efficiency of the heights to several millimeters was developed in [12].

Electromagnetic Properties of an Individual SWCNT
The electromagnetic spectroscopy at the optical ranges for an individual SWCNT were studied experimentally as in [13][14] for an armchair SWCNT10,10 and SWCNT21,21.In those results, the demonstration of a clear plasmonic signature due to the electrons transitions was reported.Now, to retrieve the dispersive refractive index, n(λ), that to be used in this study, the same two suggested scenarios in [1][2]

SWCNT Arrays Electromagnetic Properties based Vertical Alignment
The electromagnetic properties in terms of the effective refractive index, neff, of the vertically aligned SWCNT arrays are retrieved in this section.The aim of that is to perform the effective surface that to be used later on to design the UC-PBG structure.Now, the SWCNT10,10 of length 10 nm are aligned in vertical arrays with a separation distance of 2 nm from center to center.This array is realized inside a virtual waveguide based on the effective medium theory   Now, to study the performance of the proposed UC-PBG structure, the scattering parameters in terms of extinction cross section spectra are computed using both HFSS and CSTMWS, see   this band; however, the field distribution is affected between 400 nm and 500 nm due to the effect of the structure resonance as can be seen in Figure (8).with published optical spectroscopy measurements in [2].The retrieved effective electromagnetic properties are to create the effective surface that would be used for the UC-PBG construction.It is found the constructed UC-PBG shows a maximum transmitted power around 450 nm with insignificant chromatic apparitions.Nevertheless, the electromagnetic field distribution is found to be in the same direction for the most visible bands.Finally, the obtained results from FEM approach are compared against to the numerical simulation based FIT method for validation.An excellent agreement is achieved between the simulated and measured results for the SCS of an individual SWCNT.

Figure 1 :
Figure 1: The numerical results of SCS verses measurements

[
16] by applying the periodical boundary conditions along the length, where, the upper and Vol: 14 No:1, January 2018 DOI : http://dx.doi.org/10.24237/djps.1401.243AP-ISSN: 2222-8373 E-ISSN: 2518-9255 lower faces are considered Perfect Electrical Conductor (PEC) and the other two sides are assumed Perfect Magnetic Conductor (PMC) as shown in Figure (2(a)).The excitations are applied at the two ends of the waveguide as wave ports.Figure (2(b)) displays the obtained scattering parameters, reflection and transmission, from both HFSS and CSTMWS.

Figure 2 :
Figure 2: Vertical array of SWCNTs based HFSS and CSTMWS simulations; (a) The numerical setup, where, the yellow arrows are the excitation ports and (b) The obtained scattering parameters

Figure 3 :Figure 4 :
Figure 3: The retrieved neff of the vertical SWCNT array in terms of real and imaginary parts

Figure ( 5 )
Figure(5), then, compared to each other.From the presented results in Figure(5), it is found that the proposed UC-PBG structure shows the maximum scattering around 400 nm, which it may be attributed to the Rayleigh scattering.In this observation, the scatterer dimensions are relatively comparable to the half incident wave length at 400 nm.In addition to the same manner, this is attributed to electrical resonance of the scatterer length with respect to the incident light.Finally, this observation is agreed with obtained results from both HFSS and CSTMWS.

Figure 5 :
Figure 5: The extinction cross section spectra of the proposed UC-PBG structure

Figure 6 :Figure 7 :
Figure 6: The dispersion diagram of the proposed UC-PBG structure

Figure 8 :
Figure 8: The electromagnetic field distributions on the surface of the proposed UC-PBG structure