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The exceptional material properties of Lithium Niobate (LiNbO3) make it an excellent material platform for a wide range of RF, MEMS, phononic and photonic applications; however, nano-micro scale device concepts require high fidelity processing of LN films. Here, we reported a highly optimized processing methodology that achieves a deep etch with nearly vertical and smooth sidewalls. We demonstrated that Ti/Al/Cr stack works perfectly as a hard mask material during long plasma dry etching, where periodically pausing the etching and chemical cleaning between cycles were leveraged to avoid thermal effects and byproduct redeposition. To improve mask quality on X- and Y-cut substrates, a H2-plasma treatment was implemented to relieve surface tension by modifying the top surface atoms. Structures with etch depths as deep as 3.4 µm were obtained in our process across a range of crystallographic orientations with a smooth sidewall and perfect verticality on several crystallographic facets. [ABSTRACT FROM AUTHOR]

Decoupling the electronic thermal and electrical conductivities is one of the limitations hindering a breakthrough in thermoelectric efficiency. After a conformal surface coating of bismuth telluride nanowires (Bi2Te3 NWs) by porphyrins, the thermal conductivity increases from 0.8 to 1.0 Wm-1K-1 at 300 K without any obvious change in electrical conductivity. Density Functional Theory (DFT) calculations assisted by Boltzmann Transport Equation (BTE) simulations of electronic transport properties indicate that the electronic thermal transport is enhanced by the depletion of surface charge carriers, which results in transition from metallic to semiconducting behavior. Thus, the adsorption of porphyrin onto the Bi2Te3 NWs layer suppresses the surface electronic conduction, resulting in thermal electronic conduction dictated by the bulk of the NW. The results mean that electronic thermal transport can be decoupled from the electrical conductivity by changing the density of surface states on Bi2Te3 NWs. [ABSTRACT FROM AUTHOR]

Angular scatterometry is used to characterize the nanostructure parameters of two samples: a high dielectric contrast ∼100-nm period Al wire-grid polarizer (WGP), and a low dielectric contrast ∼130-nm period photoresist grating on a flexible polycarbonate substrate; both fabricated by nanoimprint lithography. The zero-order diffraction (reflection) is monitored for a large incident angle range from 8° to 80°. For the WGP, four wavelengths (244-, 405-, 633-, and 982-nm) are used to study the dependence of the scatterometry parametric determination as a function of the sample pitch to wavelength ratio (p/λ: 0.41-0.1). A 4-nm thick native Al2O3 layer was added to the scatterometry simulation and dramatically improved the cross-correlations between results at the different wavelengths. For the photoresist samples, the scatterometry results at 405 nm are compared with atomic force microscopy measurements and the master grating structure. The scatterometry results are sensitive to inhomogeneity of the sample and show a capability for classifying different types of macroscopic defects. [ABSTRACT FROM AUTHOR]

The paper presents an innovative interdisciplinary study focusing on the gilded/ polychrome decoration emulating stone-like surfaces of a Rococo Retable from Saint Francis Church in Viseu, Portugal. This study was undertaken within a 3-year research project, abbreviated Gilt- Teller (http://www.gilt-teller.pt). For the characterization of the altarpiece's polychromy a representative number of samples were analyzed using a multi-technique methodology: Optical Microscopy coupled with fluorescent staining tests, microFTIR/FTIR and microRaman spectroscopy, micro-computerized tomography, Scanning Electron Microscopy coupled with energy dispersive X-ray spectrometry. Preliminary results reveal the stratigraphical and compositional characteristics of the polychromy: ground layers made of gypsum, anhydrite, calcium carbonate and animal glue; bole layers of red ochre color (Hematite); Au/Cu/Ag metal leaf, coated with shellac; marble-like polychromy made with blue, white and red pigments (Prussian blue, Lead white, Hematite, Vermillion) and "golden particles" (Cu-Zn alloy ink-type) applied in the form of fine lines on their shaft or on the round-shaped base of the columns. [ABSTRACT FROM AUTHOR]

We have characterized the structure and electrical properties of p-type nanocrystalline silicon films prepared by radio-frequency plasma-enhanced chemical vapor deposition and explored optimization methods of such layers for potential applications in thin-film solar cells. Particular attention was paid to the characterization of very thin (&#876420 nm) films. The cross-sectional morphology of the layers was studied by fitting the ellipsometry spectra using a multilayer model. The results suggest that the crystallization process in a high-pressure growth regime is mostly realized through a subsurface mechanism in the absence of the incubation layer at the substrate-film interface. Hydrogen plasma treatment of a 22-nm-thick film improved its electrical properties (conductivity increased more than ten times) owing to hydrogen insertion and Si structure rearrangements throughout the entire thickness of the film. [ABSTRACT FROM AUTHOR]

The approach for selective growth of 1D nanostructured oxide materials using poly (dimethylsiloxane) (PDMS) stamp consists of using microcontact printing, as such the soft lithography technique, for transferring the pattern of ZnO film on a substrate, followed by the hydrothermal growth of 1D nanowires on patterned areas. The nanowires have been grown in aqueous solutions of zinc nitrate at temperature at 95°C. The wettability of the glass and of the Si/SiO2 substrates was investigated by contact angle measurements. The morphology of the nanostructures obtained was characterized by optical microscopy and scanning electron micoscopy. [ABSTRACT FROM AUTHOR]

Film stress and refractive index play an important role in the fabrication of suspended waveguides. SiO2 waveguides were successfully fabricated on multiple substrates including Si, Ge, and Al2O3 wafers; the waveguides were deposited using inductively coupled plasma chemical vapor deposition at 100 °C. The precursor gases were SiH4 and N2O at 1:3 and 1:9 ratios with variable flow rates. The occurrence of intrinsic stress was validated through the fabrication of suspended SiO2 bridges, where the curvature of the bridge corresponded to measured intrinsic stress, which measured less than 1 µm thick and up to 50 µm in length. The flow rates allow film stress tunability between 50 and −65 MPa, where a negative number indicates a compressive state of the SiO2. We also found that the gas ratios have a slight influence on the refractive index in the UV and visible range but do not affect the stress in the SiO2 bridges. To test if this method can be used to produce multi-layer devices, three layers of SiO2 bridges with air cladding between each bridge were fabricated on a silicon substrate. We concluded that a combination of low temperature deposition (100 °C) and photoresist as the sacrificial layer allows for versatile SiO2 bridge fabrication that is substrate and refractive index independent, providing a framework for future tunable waveguide fabrication. [ABSTRACT FROM AUTHOR]

We have characterized the structure and electrical properties of p-type nanocrystalline silicon films prepared by radio-frequency plasma-enhanced chemical vapor deposition and explored optimization methods of such layers for potential applications in thin-film solar cells. Particular attention was paid to the characterization of very thin (&#876420 nm) films. The cross-sectional morphology of the layers was studied by fitting the ellipsometry spectra using a multilayer model. The results suggest that the crystallization process in a high-pressure growth regime is mostly realized through a subsurface mechanism in the absence of the incubation layer at the substrate-film interface. Hydrogen plasma treatment of a 22-nm-thick film improved its electrical properties (conductivity increased more than ten times) owing to hydrogen insertion and Si structure rearrangements throughout the entire thickness of the film. [ABSTRACT FROM AUTHOR]