A simple
and convenient nanofabrication method is proposed to achieve
nanopillar arrays by the pattern transfer of an anodic aluminum oxide
membrane, profiting from the rapid and efficient preparation process
and regular hexagonal lattice patterns of the anodic aluminum oxide
template. The taper angle of the nanopillar is affected by the distribution
of the vapor particles during the deposition process, which is highly
dependent on the material and deposition power. Based on this method,
a novel scheme employing aluminum nanopillar arrays is demonstrated
to realize the color tuning feature by simply varying the thickness
of the top dielectric layer within a large range. The nanopillar arrays
are completely covered by the thick dielectric layer atop due to the
great conformality of the atomic layer deposition method that is used
for the dielectric deposition. In addition, the color devices present
good angular insensitivity up to 45°, resulting from the excited
localized surface plasmon resonance within the metallic patches. The
simple fabrication method is of great advantage to produce periodic
nanostructures over large areas, which are widely used in designs
and verifications of optical metasurfaces for various applications,
including optical communication, imaging, sensing, and so forth.
A novel scheme of an all-dielectric metasurface with double-layer patch array is proposed to achieve the highly tunable, narrowband notch filtering across visible and near-infrared range. The all-dielectric metasurface presents efficient blocking (transmittance 0.01-0.0001) at targeted wavelength and high (>93%) transmission across the visible and near-infrared light range outside the targeted wavelength band. The bandwidth of the notch filter could be greatly compressed with this all-dielectric metasurface, compared with those typical interference notch filters for distinctive wavelengths. The effect of the geometrical parameters on the spectral filtering of this metasurface is studied to provide a distinct relationship to design the desired narrowband notch filter conveniently. And the antireflection effect of the top silicon dioxide layer is verified with similar bandwidth, lower transmission at notch filtering wavelength and higher transmission at other wavelengths. In addition, the optical Fano resonance excited by the all-dielectric metasurface is responsible for the spectral filtering feature including the deep blocking feature at the specific wavelength and high transmission at other wavelengths.
TiO2-organic thin films were fabricated on SAMs-coated silicon substrate based on layer-by-layer self-assembly process and chemical bath deposition method by a hydrolysis of TiCl4 in acid aqueous solution. The influences of deposition time and solution pH value on structural properties and the thickness of TiO2 films were investigated. The results of UV-vis spectrum show the absorbance of aqueous solutions at 410 nm decreases gradually with increasing deposition time and solution pH value. The thickness of TiO2-organic thin film elevates as increasing deposition time and pH value. The deposition time has significant influence on the surface morphology of films, and when the time is 2 h, a continuous, density and homogeneous film is gained from SEM micrographs. The deposited films consisting of TiO2 nanoparticles are believed to be fully amorphous layers from the results of XRD. The major chemical compositions of thin films are titanium and oxygen as presented in EDS results, and O/Ti atomic ratio is close to the corresponding ratio of 2:1 for stoichiometric TiO2. The transmission infrared spectrum and UV/Vis spectrum of TiO2 film indicate excellent structure and optical properties of films.
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