Surface Texturing of n- and p-Doped c-Si Using a Novel Plasma Chemical Texturing Process

Abstract n- and p-doped c-Si (100) are textured by a SF 6 /O 2 plasma chemical etching, under conditions avoiding ion bombardment. The study of the effects of plasma parameters on morphology and on surface reflectance of textured c-Si reveals a strong impact of silicon doping on texturing characteristics. SF 6 /O 2 plasma etches anisotropically n-type c-Si creating a square-based hillock-like morphology with a surface reflectivity of 6%. Conversely, for p-type Si, a H 2 plasma pretreatment is necessary to activate silicon etching and obtain a nano-textured surface with a reflectivity of 16%

Demonstration of improved charge transfer in graphene/Au nanorods plasmonic hybrids stabilized by benzyl thiol linkers

Hybrids based on graphene decorated with plasmonic gold (Au) nanostructures are being investigated as possible materials combination to add to graphene functionalities of tunable plasmon resonance and enhanced absorption at selected wavelength in the visible-near-infrared region of the spectrum. Here, we report a solution drop-casting approach for fabricating stable hybrids based on chemical vapor deposition (CVD) graphene and Au nanorods, which are able to activate effective charge transfer from graphene. We demonstrate that CVD graphene functionalization by benzyl thiol (BZT) provides the linker to strong anchoring, via S-Au bonds, Au nanorods to graphene. Optical measurements by spectroscopic ellipsometry give evidence of the introduction of plasmon resonances at 1.85 and 2.25 eV in the Au nanorods/BZT/graphene hybrids, which enable surface enhanced Raman scattering (SERS) detection. Furthermore, an effective electron transfer from graphene to Au nanorods, resulting in an enhancement of p-type doping of graphene with a consequent decrease of its sheet resistance, is probed by Raman spectroscopy and corroborated by electrical measurements

Dielectric function of nanocrystalline silicon with few nanometers (<3 nm) grain size

The dielectric function of nanocrystalline silicon (nc-Si) with crystallite size in the range of 1 to 3 nm has been determined by spectroscopic ellipsometry in the range of 1.5 to 5.5 eV. ATauc–Lorentz parameterization is used to model the nc-Si optical properties. The nc-Si dielectric function can be used to analyze nondestructively nc-Si thin films where nanocrystallites cannot be detected by x-ray diffraction and Raman spectroscopy

Physical activity promotion of ethnic populations in deprived communities : From determinants to intervention

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Reconfigurable and optically transparent microwave absorbers based on deep eutectic solvent-gated graphene

Abstract Electrolytically tunable graphene “building blocks” for reconfigurable and optically transparent microwave surfaces and absorbers have been designed and fabricated by exploiting Deep Eutectic Solvents (DESs). DESs have been first explored as electrolytic and environmentally friendly media for tuning sheet resistance and Fermi level of graphene together with its microwave response (reflection, transmission and absorption). We consider the tunability of the reconfigurable surfaces in terms of transmittance, absorption and reflectance, respectively, over the X and Ku bands when the gate voltage is varied in the −1.4/+1.4 V range. The numerical simulations and experimental measurements also show the ability of the absorber, in the Salisbury screen configuration, to achieve near perfect absorption with a modulation of about 20%. These results could find applications in several technological fields, ranging from electromagnetic pollution to integrated multi-physical regulation systems, thereby helping the advance of the performance of microwave cloaking systems, stealth windows, frequency selective surfaces, modulators and polarizers

Optically Transparent Microwave Polarizer Based on Quasi-Metallic Graphene

In this paper, we report on the engineering and the realization of optically transparent graphene-based microwave devices using Chemical Vapour Deposition (CVD) graphene whose sheet resistance may be tailored down to values below 30Ω/sq. In particular, we show that the process was successfully used to realize and characterize a simple, optically transparent graphene-based wire-grid polarizer at microwave frequencies (X band). The availability of graphene operating in a quasi-metallic region may allow the integration of graphene layers in several microwave components, thus leading to the realization of fully transparent (and flexible) microwave devices

Interplay between solid-state organization and optical properties of thin films of poly-arylene-vinylene and -difluorinated vinylene: Fullerene blends

application in organic polymer solar cells. A large variety of low bandgap polymers are prepared by alternating copolymerization of electron-donating donor and electron-withdrawing acceptor units. The interaction between these two units can reduce the polymer bandgap, increasing the sunlight absorption. Benzothiadiazole is commonly used as acceptor block unit in low bandgap polymers. In this contribution we investigate the supramolecular organization and optical properties of thin films of conjugated polymers consisting of benzothiadiazole and thiophene with electron-withdrawing difluorovinylene, and electron-donating vinylene substituents. Atomic force microscopy and spectroscopic ellipsometry are exploited for the analysis of the morphology and optical transitions, respectively. It is found that F-atoms in the vinylene unit yield a blue-shift of the absorption peaks of 0.2 eV respect to the hydrogenated polymer and an increase in the absorption coefficient of fluorinated polymers, which indicates their potential application as photovoltaic material. The morphology evolution of the conjugated polymers blended with a fullerene derivate ([6,6]-phenyl C61-butyric acid methyl ester, PCBM) is also investigated by atomic force microscopy.??