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Author: Lotnyk, Andriy × DDC: 530 × Publisher: Weinheim : Wiley-VCH × WGL Institute: IOM ×

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    Biaxially Textured Titanium Thin Films by Oblique Angle Deposition: Conditions and Growth Mechanisms
    (Weinheim : Wiley-VCH, 2020) Liedtke-Grüner, Susann; Grüner, Christoph; Lotnyk, Andriy; Gerlach, Juergen W.; Rauschenbach, Bernd
    Growing highly crystalline nanowires over large substrate areas remains an ambiguous task nowadays. Herein, a time-efficient and easy-to-handle bottom-up approach is demonstrated that enables the self-assembled growth of biaxially textured Ti thin films composed of single-crystalline nanowires in a single-deposition step. Ti thin films are deposited under highly oblique incidence angles by electron beam evaporation on amorphous substrates. Substrate temperature, angle of the incoming particle flux, and working pressure are varied to optimize the crystallinity in those films. Height-resolved structure information of individual nanowires is provided by a transmission electron microscopy (TEM) nanobeam, high-resolution TEM, and electron diffraction. Ti nanowires are polycrystalline at 77 K, whereas for ≥300 K, single-crystalline nanowires are tendentially found. The Ti crystals grow along the thermodynamically favored c-direction, but the nanowires’ tilt angle is determined by shadowing. Biaxially textured Ti thin films require a certain temperature range combined with highly oblique deposition angles, which is proved by X-ray in-plane pole figures. A general correlation between average activation energy for surface self-diffusion and melting point of metals is given to estimate the significant influence of surface self-diffusion on the evolution of obliquely deposited metal thin films.
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    Compositional Patterning in Carbon Implanted Titania Nanotubes
    (Weinheim : Wiley-VCH, 2021) Kupferer, Astrid; Holm, Alexander; Lotnyk, Andriy; Mändl, Stephan; Mayr, Stefan G.
    Ranging from novel solar cells to smart biosensors, titania nanotube arrays constitute a highly functional material for various applications. A promising route to modify material characteristics while preserving the amorphous nanotube structure is present when applying low-energy ion implantation. In this study, the interplay of phenomenological effects observed upon implantation of low fluences in the unique 3D structure is reported: sputtering versus readsorption and plastic flow, amorphization versus crystallization and compositional patterning. Patterning within the oxygen and carbon subsystem is revealed using transmission electron microscopy. By applying a Cahn–Hilliard approach within the framework of driven alloys, characteristic length scales are derived and it is demonstrated that compositional patterning is expected on free enthalpy grounds, as predicted by density functional theory based ab initio calculations. Hence, an attractive material with increased conductivity for advanced devices is provided. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH