Exact comprehensive equations for the photon management properties of silicon nanowire (original) (raw)
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Optical Properties of Individual Silicon Nanowires for Photonic Devices
ACS Nano, 2010
Silicon is a high refractive index material. Consequently, silicon nanowires (SiNWs) with diameters on the order of the wavelengths of visible light show strong resonant field enhancement of the incident light, so this type of nanomaterial is a good candidate for all kinds of photonic devices. Surprisingly enough, a thorough experimental and theoretical analysis of both the polarization dependence of the absorption and the scattering behavior of individual SiNWs under defined illumination has not been presented yet. Here, the present paper will contribute by showing optical properties such as scattering and absorption of individual SiNWs experimentally in an optical microscope using bright-and dark-field illumination modes as well as in analytical Mie calculations. Experimental and calculation results are in good agreement, and both reveal a strong correlation of the optical properties of individual SiNWs to their diameters. This finding supports the notion that SiNWs can be used in photonic applications such as for photovoltaics or optical sensors.
Low cost synthesis of silicon nanowires for photonic applications
Journal of Materials Science: Materials in Electronics
Achieving light management in nanostructured materials is a recent challenge of great resonance among the scientific community, which is generally attained by expensive surface patterning requiring advanced technologies. In this paper, we report the realization of 2D random fractal arrays of silicon nanowires (NWs) synthesized with a low cost approach compatible with Si technology, without the use of any lithography or mask. Their innovative photonic properties are exploited in comparison to non-fractal nanowires. In particular, a remarkable room temperature luminescence is attained in Si NWs due to quantum confinement effect. The NWs fabrication was engineered in order to produce two-dimensional random fractal arrays of Si NWs whose structural properties were investigated and compared to other non-fractal Si NW systems. The impressive light trapping and strongly enhanced Raman signal of our fractal Si NW array is of significant interest for potential applications spanning from photonics, to photovoltaics and sensing.
A Model Study of Surface State on Optical Bandgap of Silicon Nanowires
Science World Journal, 2015
A theoretical approach is carried out to study the role of surface state in silicon nanowires. The influences of size and surface passivation on the bandgap energy and photoluminescence spectra of silicon nanowires with diameter between 4 to 12nm are examined. It is observed that visible PL in silicon nanowires is due to quantum confinement and surface passivation. But the energy recombination of electron and holes in the quantum confined nanostructures is responsible for the visible PL. In this work, models from quantum bandgap and photoluminescence intensity are adopted to explain the size dependent surface luminescence. Investigation show that the nanowires of smaller size with surface impurities revealed higher bandgap energy. Oxygenated surface is found to have higher energy than hydrogenated surface. The features of PL spectra of Si nanowires suggest that these models are significant for understanding the mechanism of visible PL from SINWs.
Spatial delocalization of absorption and emission process in silicon nanowires
Journal of Luminescence, 2019
Dependence of optical properties of porous silicon nanowires on their size has been investigated here. Based on the experimental evidence, a new model to explain the process of absorption and photoluminescence in these Si nanowire samples has been proposed. Three different samples, with different nanowire diameters, have been prepared using metal-induced etching of silicon wafers. These wafers have different doping type and doping concentration which results in silicon nanowires of different diameters embedded with Si nanostructures of sizes around the Bohr's exciton radius. The absorption properties of these different types of Si nanostructures show a strong size dependence. However, the photoluminescence spectrum does not show any direct dependence on the size of the nanostructures, doping levels and type of silicon wafer used for fabrication of silicon nanostructures. It is also observed that the photoluminescence life time from these structures inversely depends on the size of the nanostructures whereas directly depends on the porosity, thus defects, in the samples. Based on these results it has been shown that the absorption of photons in these porous silicon nanowires happens in the silicon nanostructures embedded in the nanowires while the photoluminescence emission originates due to the surrounding porous SiO x .
Modal analysis of enhanced absorption in silicon nanowire arrays
Optics Express, 2011
We analyze the absorption of solar radiation by silicon nanowire arrays, which are being considered for photovoltaic applications. These structures have been shown to have enhanced absorption compared with thin films, however the mechanism responsible for this is not understood. Using a new, semi-analytic model, we show that the enhanced absorption can be attributed to a few modes of the array, which couple well to incident light, overlap well with the nanowires, and exhibit strong Fabry-Pérot resonances. For some wavelengths the absorption is further enhanced by slow light effects. We study the evolution of these modes with wavelength to explain the various features of the absorption spectra, focusing first on a dilute array at normal incidence, before generalizing to a dense array and off-normal angles of incidence. The understanding developed will allow for optimization of simple SiNW arrays, as well as the development of more advanced designs.
Silicon Nanoscale Materials: From Theoretical Simulations to Photonic Applications
International Journal of Photoenergy, 2012
The combination of photonics and silicon technology is a great challenge because of the potentiality of coupling electronics and optical functions on a single chip. Silicon nanocrystals are promising in various areas of photonics especially for light-emitting functionality and for photovoltaic cells. This review describes the recent achievements and remaining challenges of Si photonics with emphasis on the perspectives of Si nanoscale materials. Many of the results and properties can be simulated and understood based on theoretical studies. However, some of the key questions like the light-emitting mechanism are subjects of intense debates despite a remarkable progress in the recent years. Even more complex and important is to move the known experimental observations towards practical applications. The demonstrated devices and approaches are often too complex and/or have too low efficiency. However, the challenge to combine optical and electrical functions on a chip is very strong, and we expect more research activity in the field of Si nanophotonics in the future.
-Single nanowire solar cells (SNSCs) are typical nanoscale optoelectronic devices with unique photonic and electronic properties which require precise designs in terms of a comprehensive simulation technique. We present a coupled model for silicon-based SNSCs which solves both Maxwell and semiconductor equations self-consistently using finite element method. The light-trapping behavior (e.g., leaky-mode resonances) and carrier generation/recombination inside the nanowire cavity are simulated and analyzed with especially addressing the effects of semiconductor doping, surface recombination and device dimension on the performance of the solar cells. The absorption efficiency, external quantum efficiency, and current-voltage characteristics have been obtained for a complete evaluation of SNSCs.