Al Nanoparticle Arrays Research Articles

Broadband ultraviolet plasmonic enhanced AlGaN/GaN heterojunction photodetectors with close-packed Al nanoparticle arrays.

Plasmonic metallic nanostructures could concentrate optical fields into nanoscale volumes and support efficient light scattering and absorption, which therefore stimulates the continuing development of advanced plasmonic-assisted semiconductor photodetectors. In this work, by fabricating Al nanoparticle (NP) arrays in AlGaN surface using the AAO template transferring method, significant broadband ultraviolet (UV) photoresponse enhancement was demonstrated on AlGaN/GaN heterojunction photodetectors. By deliberately designing the close-packed Al NP arrays, the broadband UV plasmonic resonance with large optical field absorption and strong interface field enhancement are enabled, hence, the highest responsivity exceeding 8.1 A W-1 and maximum external quantum efficiency of 3500% was obtained at the resonance wavelength 292 nm, revealing more than 80 times the excellent enhancement in responsivity. Specifically, owing to coupling among NPs at the Al/AlGaN interface, the smaller size Al NP array exhibits an excellent photoresponse enhancement encompassing the entire UV band compared to the relatively larger size Al NP array. In addition, different photoresponse enhancements depending on the applied bias were observed. The Al NPs detector also demonstrates a fast photoresponse with a rise time of around 60 ms and a relatively long fall time of 1.42 s. This work could be of great significance for gaining a low and efficient approach to achieve plasmonic-empowered heterojunction broadband UV detectors.

Facile fabrication of Al nanoparticle arrays with continuous tunable diameter and plasmonic band for UV–visible SERS detection

Al-based nanostructures have a huge potential for surface-enhanced Raman scattering (SERS) in area of life science, chemical and food safety because of its excellent plasmonic characteristics from UV to near-infrared ranges. By only controlling the deposited Al thickness onto the parabola-shaped alumina nanopores template, the Al nanoparticle arrays with tunable diameter from 55 nm to 94 nm and plasmonic bands ranging from 285 nm to 717 nm were obtained. With excitation at UV and visible plasmon resonance wavelength (325 nm, 633 nm), the experimental SERS enhancement factor (EF) reached 103 and relative standard deviation (RSD) below 10% on a large scale. Finite-difference time-domain (FDTD) simulations reveal electric field intensity and charge distribution of dipolar and quadrupolar plasmon mode. The simple and controllable fabrication strategy and superior SERS performance in UV–visible range make the Al nanoparticle arrays promising candidates for SERS-based sensor applications. And the method provides a new approach for developing an inexpensive, efficient, and mass-produced Al-based SERS active substrate.

Localized surface plasmon and transferred electron enhanced UV emission of ZnO by periodical aluminum nanoparticle arrays

Periodical Al nanoparticle (NP) arrays were applied to enhance the ultraviolet (UV) light emission of ZnO by localized surface plasmon resonance (LSPR) effect and electron transfer mechanism. By applying corresponding anodic aluminum oxide (AAO) templates, periodical Al NP arrays with different diameters (D) and spaces (S) were manufactured by magnetron sputtering. Theoretical simulation by FDTD-solution indicates that local electric field around Al NPs is significantly enhanced, and the surface plasmon resonance wavelength is determined by D and S. Al NP arrays with D of 70 nm and S of 125 nm enhanced near band-edge emission of ZnO by 2.4 times. By adding Al NP arrays, the photonic lifetime of ZnO decreased by 0.09 ns according to time-resolved photoluminescence spectra, indicating that the enhancement in UV luminescence intensity of ZnO is ascribed to the coupling between surface plasmons of Al NPs and ZnO excitons. Deep-level emission spectra analysis indicates that there lies another mechanism of electron transfer from the Al NPs to surface plasmon resonance (SPR) level and then further to ZnO conduction band.

Influence of order-to-disorder transitions on the optical properties of the aluminum plasmonic metasurface.

To mimic the optical influence of disorder in condensed matter, the effect of uniform disorder on plasmonic resonances were investigated numerically and experimentally on aluminum (Al) nanoparticle arrays. Resorting to the analogue of a plasmonic periodic array to a crystal on the sharp optical spectrum and its anisotropy, the disorder in the transition from crystal to glass (with broadened spectrum and isotropy) is imitated by three kinds of Al plasmonic metasurfaces: varying the displacement, size and rotation of each Al nanoparticle in the periodic array. The random variation on the location or size of each Al nanodisk in the plasmonic crystal induces broadening and reduction of their plasmonic resonances without significantly shifting its wavelength. Moreover, by rotating each Al nanorod in the plasmonic crystal by a random angle, the polarization dependence of plasmonic resonances is progressively decreased by increasing the rotation disorder. Thanks to these three kinds of Al metasurfaces, an enlightened understanding of the random physics in the solid state and the influence of manufacturing deviation in nanophotonics is supported.

Increased Absorption with Al Nanoparticle at Front Surface of Thin Film Silicon Solar Cell

This article presents an effective structural design arrangement for light trapping in the front surface of a thin film silicon solar cell (TFSC). Front surface light trapping rate is significantly enhanced here by incorporating the Aluminium (Al) nanoparticle arrays into silicon nitride anti-reflection layer. The light trapping capability of these arrays is extensively analyzed via Finite Difference Time Domain (FDTD) method considering the wavelength ranging from 400 to 1100 nm. The outcome indicates that the structural parameters associated with the aluminium nanoparticle arrays like particle radii and separations between adjacent particles, play vital roles in designing the solar cell to achieve better light trapping efficiency. A detailed comparative analysis has justified the effectiveness of this approach while contrasting the results found with commonly used silver nanoparticle arrays at the front surface of the cell. Because of the surface plasmon excitation, lower light reflectance, and significant near field enhancement, aluminium nanoparticle arrays offer broadband light absorption by the cell.

Plasmon nanolasing with aluminum nanoparticle arrays [Invited

This paper compares plasmon nanolasing and corresponding ultrafast dynamics supported by Al and Au nanoparticle arrays. By tuning nanoparticle size, we achieved high-quality surface lattice resonances from both dipolar lattice plasmons and hybrid quadrupolar lattice plasmons at near-infrared wavelengths. We demonstrated that the dipolar and hybrid quadrupolar lattice modes can serve as optical feedback for plasmonic nanolasing. Even at the wavelength of its interband transition, Al showed nanolasing properties similar to Au. Also, independent of the type of cavity mode used as optical feedback, Al lattice plasmon lasing showed thresholds and ultrafast dynamics similar to Au.

Evolution and Tailoring of DUV Plasmonic Properties in Al Nanoparticle Arrays by UV Irradiation

Ultraviolet irradiation was used to tailor the surface plasmon band of the densely distributed aluminium nanoparticle arrays fabricated by gas-phase deposition. We showed that the broad surface plasmon resonance band of the as-prepared sample could be tuned to a sharp and strong resonance band in the deep ultraviolet optical range, with a large blue shift of the peak wavelength. The evolution of the surface plasmon resonance properties was attributed to the ultraviolet irradiation-improved surface oxidation of the nanoparticles, which eliminated the near-field couplings between the closely spaced nanoparticles by increasing their interspacing.

Plasmon enhancement of optical absorption in ultra-thin film solar cells by rear located aluminum nanodisk arrays

In this work, in order to enhance the light absorption in one micron thick crystalline silicon solar cells, a back reflecting and rear located plasmonic nanodisk scheme is proposed. We investigate the scattering properties of aluminum nanostructures located at the back side and optimize them for enhancing absorption in the silicon layer by using finite difference time domain simulations. The results indicate that the period and diameters of nanodisks, thickness of spacer layer have a strong impact on short circuit current enhancements. The optimized Al nanoparticle arrays embedded in rear located SiO2 layer enhance Jsc with an increase of 47% from the non-plasmonic case of 18.9 to 27.8 mA/cm2 when comparing with a typical stack with a planar aluminum back reflector and a back reflector with plasmonic nanoparticles. This finding could lead to improved light trapping within a thin silicon solar cell device.

Broadband photocurrent enhancement and light-trapping in thin film Si solar cells with periodic Al nanoparticle arrays on the front.

Plasmonic resonances in metal nanoparticles are considered candidates for improved thin film Si photovoltaics. In periodic arrays the influence of collective modes can enhance the resonant properties of such arrays. We have investigated the use of periodic arrays of Al nanoparticles placed on the front of a thin film Si test solar cell. It is demonstrated that the resonances from the Al nanoparticle array causes a broadband photocurrent enhancement ranging from the ultraviolet to the infrared with respect to a reference cell. From the experimental results as well as from numerical simulations it is shown that this broadband enhancement is due to single particle resonances that give rise to light-trapping in the infrared spectral range and to collective resonances that ensure an efficient in-coupling of light in the ultraviolet-blue spectral range.

High-performance AlGaN metal–semiconductor–metal solar-blind ultraviolet photodetectors by localized surface plasmon enhancement

AlGaN-based solar-blind ultraviolet photodetectors have attractive potential applications in the fields of missile plume detection, biochemical sensing, solar astronomy, etc. In this work, significant deep ultraviolet detection enhancement is demonstrated on AlGaN-based metal–semiconductor–metal (MSM) solar-blind ultraviolet photodetectors by introducing the coupling of localized surface plasmon from Al nanoparticles with the high-Al-content AlGaN epilayer. The size-controlled Al nanoparticle arrays fabricated by nanosphere lithography can not only reduce the detectors' dark current but also bring about greatly enhanced responsivity. The peak responsivity of AlGaN-based MSM solar-blind ultraviolet photodetectors with Al nanoparticles can reach 2.34 A/W at 269 nm under 20 V bias, enhanced more than 25 times than that without Al nanoparticles. Our approach shows an efficient fabrication technique of high-performance and low-cost plasmonic enhanced AlGaN solar-blind MSM ultraviolet photodetectors.

Numerical simulation of light absorption enhancement in microcrystalline silicon solar cells with Al nanoparticle arrays

Metal nanoparticles with low cost and high performance have good potential applications in light-trapping of solar cells. In this paper, a three-dimensional model is proposed to simulate the light absorption of microcrystalline silicon (μc-Si:H) thin film solar cells. The effects of spherical and hemispherical Al nanoparticle arrays located on the front surfaces of solar cells are investigated, and the particle radius and array period are optimized by the finite element method. The results show that the optimal Al nanoparticle arrays can enhance broadband absorption in thin film solar cells. For spherical particle arrays, the key parameter that influences light absorption in solar cells is period/radius ratio (P/R) or particle surface coverage. When P/R=4-5, the optimum integrated absorption enhancement (Eabs) is over 20% under AM1.5 illumination compared with the solar cell without nanoparticles. The value of Eabs is small and decreases with the increase of P/R when P/R>5, and Eabs is less than zero when P/RP=500 nm and R=120 nm, the spectral absorption rate as a function of wavelength shows broadband absorption including four distinct peaks, which are attributed to quadrupole plasmon resonance mode, dipole resonance mode and waveguide mode respectively according to the electric field distribution in the solar cell. For hemispherical particle arrays, the maximum value of Eabs is 24.5%, which is higher than that of the solar cell with optimized spherical particle arrays. This is due to the high coupling efficiencies of the particles, so that most of the scattered light is directly coupled into the substrate. However, the value of Eabs is very sensitive to the hemispherical particle radius. As the radius decreases, the scattering cross-section and scattering efficiency of the particle decrease dramatically. As the radius increases, the dipole plasmon resonance wavelength rapidly shifts towards longer wavelength (red shift). Both of these are detrimental to absorption enhancement of solar cells. Thus we conclude that spherical Al particle arrays are more preferable in actually fabricating the light-trapping of solar cells.

Loss mitigation in plasmonic solar cells: aluminium nanoparticles for broadband photocurrent enhancements in GaAs photodiodes

We illustrate the important trade-off between far-field scattering effects, which have the potential to provide increased optical path length over broad bands, and parasitic absorption due to the excitation of localized surface plasmon resonances in metal nanoparticle arrays. Via detailed comparison of photocurrent enhancements given by Au, Ag and Al nanostructures on thin-film GaAs devices we reveal that parasitic losses can be mitigated through a careful choice of scattering medium. Absorption at the plasmon resonance in Au and Ag structures occurs in the visible spectrum, impairing device performance. In contrast, exploiting Al nanoparticle arrays results in a blue shift of the resonance, enabling the first demonstration of truly broadband plasmon enhanced photocurrent and a 22% integrated efficiency enhancement.

Exceeding the limit of plasmonic light trapping in textured screen-printed solar cells using Al nanoparticles and wrinkle-like graphene sheets

AbstractThe solar cell market is predominantly based on textured screen-printed solar cells. Due to parasitic absorption in nanostructures, using plasmonic processes to obtain an enhancement that exceeds 2.5% of the short-circuit photocurrent density is challenging. In this paper, a 7.2% enhancement in the photocurrent density can be achieved through the integration of plasmonic Al nanoparticles and wrinkle-like graphene sheets. For the first time, we experimentally achieve Al nanoparticle-enhanced solar cells. An innovative thermal evaporation method is proposed to fabricate low-coverage Al nanoparticle arrays on solar cells. Due to the ultraviolet (UV) plasmon resonance of Al nanoparticles, the performance enhancement of the solar cells is significantly greater than that from Ag nanoparticles. Subsequently, we deposit wrinkle-like graphene sheets over the Al nanoparticle-enhanced solar cells. Compared with planar graphene sheets, the bend carbon layer also exhibits a broadband light-trapping effect. Our results exceed the limit of plasmonic light trapping in textured screen-printed silicon solar cells.

Deep-UV Surface-Enhanced Resonance Raman Scattering of Adenine on Aluminum Nanoparticle Arrays

We report the ultrasensitive detection of adenine using deep-UV surface-enhanced resonance Raman scattering on aluminum nanostructures. Well-defined Al nanoparticle arrays fabricated over large areas using extreme-UV interference lithography exhibited sharp and tunable plasmon resonances in the UV and deep-UV wavelength ranges. Theoretical modeling based on the finite-difference time-domain method was used to understand the near-field and far-field optical properties of the nanoparticle arrays. Raman measurements were performed on adenine molecules coated uniformly on the Al nanoparticle arrays at a laser excitation wavelength of 257.2 nm. With this technique, less than 10 amol of label-free adenine molecules could be detected reproducibly in real time. Zeptomole (~30,000 molecules) detection sensitivity was readily achieved proving that deep-UV surface-enhanced resonance Raman scattering is an extremely sensitive tool for the detection of biomolecules.