Effective medium theory to the description of plasmonic resonances: Role of Au and Ti nanoparticles embedded in MoO3 thin films

Abstract

The growing interest in functional transition metal oxides for efficient energy consumption or in the bio-sensing process; indicates that is necessary to develop a new theoretical method that describes experiments. This article presents a new theoretical methodology to characterize molybdenum trioxide (MoO 3) thin films doped with resonant gold-nanoparticles (Au-NPs) and non-resonant titaniumnanoparticles (Ti-NPs). The modulation of surface plasmon resonance (SPR) and the implications in the MoO 3 transmittance spectrum is described by applying an effective medium theory. The transmittance modulation was modified by variating three parameters, the radius of the NPs, the concentration of the NPs as well as the variation of the MoO 3 thin films thickness. It was found that the nanoparticles concentration is the most important parameter in the transmittance modulation. Additionally, the orthorhombic and monoclinic structure of MoO 3 was studied, from which it was obtained that the monoclinic structure of the MoO 3 doped with Au-NPs favors the reduction in the transmittance values in the visible region which is associated with the increase of the SPR signal. Similar analyses are performed for non-resonant nanoparticles such as Ti, where it was found that optical modulation is not as marked as the case of gold nanoparticles. Optical properties of different kind of systems has attracted attention for many researchers around the world 1-5. Developing new devices with interesting optical properties has been a technological and experimental challenge 6,7. In order to describe optical properties from a theoretical point of view, it have been developed sophisticated multiphysics modeling finite element commercial software, such as Comsol Multiphysics, Lumerical FDTD or BEM which allow you to calculate, reflection or transmission frequency-dependent or scattering parameters and near or far electromagnetic field projections. However, many of them are difficult to access since they are expensive or they are not very intuitive software's. So, implementing new theoretical formalisms to characterized and analyzed thin films with new, interesting and unexpected effects could be useful for developing new devices with different kinds of optical properties. There are some different approaches to characterize thin films 8-10 , particularly for thin films doped with different materials, using an effective medium theory to describe the radiation interaction with the doped thin films could be an alternative. In effective medium models, one of the most important approximation is the large size limit. The most studied formalisms that consider effective medium theories (EMTs) are Maxwell Garnett or Bruggeman, these models are applied to described materials with granular topology 11 and materials with intermixed components 12 , respectively. These EMTs are based on small spheres approximation, which means that the size of the particles is small compared with the incident radiation wavelength 13. An alternative formalism to study effective me...

Extinction Coefficient Modulation of MoO3 Films Doped with Plasmonic Nanoparticles: From an Effective Medium Theory Description

“…In all comparative cases, it is observed that in the β -phase of MoO 3 , the extinction coefficient peaks display the highest intensity when compared to the α -phase. This behavior is important to highlight due to the advantages in technological applications where this information could be used to simulate the visible radiation trapping layer by modifying only the molybdenum oxide phase and corroborates what was found previously [ 22 ]. Additionally, by increasing the radius size of the nanoparticle from 5 to 20 nm, the SPR signal shows a redshift in all comparative cases.…”

“…This latter configuration has generated significant interest due to the ability to modulate the absorbance in the visible range, a feature of great importance in photocatalytic applications, biological sensing, smart windows, and photovoltaic cells [ 22 ]. This property is attributed to a phenomenon called superficial plasmon resonance (SPR) [ 23 , 24 ].…”

“…To mention some of them, hot-electrons injected from plasmonic nanoparticles [ 25 ], plasmon-induced absorption [ 26 ], plasmon-induced resonance energy transfer (PIRET) [ 27 ], plasmon-mediated processes [ 28 ]. Recently, our group has developed a theoretical study that describes in detail the behavior of the SPR signal intensity in the MoO 3 transmittance spectrum when it varying the concentration of Au nanoparticles, as well as the phase of MoO 3 [ 22 ]. However, in that work, the effect of the nanoparticle size in the changes in transmittance spectrum; particularly in the SPR signal, did not show a strong dependency.…”

Structure of Randomly Distributed Nanochain Aggregates on Silicon Substrates: Modeling and Optical Absorption Characteristics

“…Several quasianalytical models have been developed for characterizing the nanoaggregate structures, including the effective medium model [ 11 ], cluster-cluster aggregation (CCA) model [ 12 ], and fractal lossy antennas (FLA) model [ 13 ]. The effective medium model simplifies complex nanoclusters into hypothetical ellipsoids.…”

Отражение Света От Плазмонных Пленок Золота И Серебра: Сравнение Эксперимента И Теории

“…Напыленные в вакууме ПМП (особенно после их термического отжига) можно представить в виде ансамбля наночастиц, самоорганизованных поверх сплошной металлической поверхности [13]. Ранее было показано [14][15][16][17][18][19][20], что расширенная теория Максвелла-Гарнетта вполне приемлема для соотнесения эффективной диэлектрической функции с подобной морфологией поверхности. Таким образом, анализ возможностей и ограничений разных моделей приводит к выбору расширенной теории Маквелла-Гарнета для моделирования процессов отражения света плазмонными металлическими пленками.…”