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The influence of one dimensional substrate patterns on the nanocolumnar growth of thin films deposited by magnetron sputtering at oblique angles is theoretically and experimentally studied. A well-established growth model has been used to study the interplay between the substrate topography and the thin film morphology. A critical thickness has been defined, below which the columnar growth is modulated by the substrate topography, while for thicknesses above, the impact of substrate features is progressively lost in two stages; first columns grown on taller features take over neighboring ones, and later the film morphology evolves independently of substrate features. These results have been experimentally tested by analyzing the nanocolumnar growth of SiO 2 thin films on ioninduced patterned substrates. K E Y W O R D S magnetron sputtering, nanostructures, oblique angle deposition, patterned substrate, thin films Plasma Process Polym. 2019;16:e1800135.www.plasma-polymers.com

We report on the bottom-up fabrication, by plasma-assisted molecular beam epitaxy, of monocrystalline GaN solid, hollow, and c-shape nanowires deposited in a compact fashion. The shape exhibited by these nanostructures varies from solid to c-shape and hollow nanowires. They were epitaxially grown with their [0001] directions perpendicular with respect to different surfaces of Si substrates. Advanced studies of these GaN nanostructures were carried out by means of selected-area electron diffraction and scanning and high-resolution transmission electron microscopy evidencing their structure and epitaxial alignments with respect to the silicon. Through a comprehensive analysis of the growth conditions (substrate temperature and Ga and N* fluxes) we demonstrate that a local Ga-limited regime is the mechanism behind the particular shape of these nanostructures. Additionally, spectroscopic ellipsometry studies, applying a model based on Bruggeman effective medium approximations and taking into account several aspects related to the nature of these GaN nanostructures, were carried out to obtain valuable information about the evolution of the optical constants and the porosity along the layer. This work shows a way to control the porosity and shape of GaN nanowires by varying the growth conditions, which could open new horizons in the development of GaN nanostructures for future applications.

In this paper, we report the fabrication of porous and crystalline tin-doped indium oxide (ITO) thin films at room temperature by ion beam sputtering deposition at oblique angles using either argon or xenon ions. Deep insights into these systems are provided by coupling nanostructural (scanning and transmission electron microscopies, X-ray diffraction) and optical (spectroscopic ellipsometry, spectral reflectometry) characterizations. This original approach allows extracting important features of the films (porosity, refractive indexes, in-grain carrier densities, and mobilities) not easy to reach locally by other techniques. We propose a model decomposing the complex film's nanostructure into two layers presenting different electro-optical properties, which are attributed to the shadowing effect, but also to the presence of growth defects and impurities due to the atomic peening. In particular, we demonstrate that ITO films deposited with Xe present a better crystallinity and larger porosity, providing superior in-grain carrier transport and offering more flexibility to design broad-band low-reflectivity surfaces. These results widen the possibilities to engineer transparent and conductive thin films at room temperature with enhanced properties, especially in the near-infrared range where oblique angle deposition allows a reduction of reflectivity even at high doping.

This work is focused on the characterization by transmission and scanning-transmission electron microscopy-related techniques of core-shell nanoparticles synthesized via chemical methods. Diferent semiconducting, pure metallic or oxide materials have been utilized as the core (cadmium telluride, gold, magnetite, or magnetite covered with gold) of the nanoparticle, while they have been, in all cases, functionalized by a thin amorphous glutathione layer, with the goal of using the nanoparticles in biomedical applications such as biomarkers, and computerized tomography and image magnetic resonance contrast agents. The results show that it is possible to visualize the glutathione layer using spectroscopic and imaging techniques, associated with electron microscopy (such as energy-dispersive X-ray spectroscopy and high-resolution transmission electron microscopy images), that this layer is present at the surfaces of all observed nanoparticles, and that it is no thicker than a few nanometers. Electron microscopy also revealed that the nanoparticles core is crystalline and, in average, around 5-nm size.