Carbon and Neon Ion Bombardment Induced Smoothing and Surface Relaxation of Titania Nanotubes

Abstract

Titania nanotube arrays with their enormous surface area are the subject of much attention in diverse fields of research. In the present work, we show that not only 60 keV and 150 keV ion bombardment of amorphous titania nanotube arrays yields defect creation within the tube walls, but it also changes the surface morphology: the surface relaxes and smoothens in accordance with a curvature-driven surface material’s transport mechanism, which is mediated by radiation-induced viscous flow or radiation-enhanced surface diffusion, while the nanotubes act as additional sinks for the particle surface currents. These effects occur independently of the ion species: both carbon and neon ion bombardments result in comparable surface relaxation responses initiated by an ion energy of 60 keV at a fluence of 1 × 1016 ions/cm2. Using atomic force microscopy and contact angle measurements, we thoroughly study the relaxation effects on the surface topography and surface free energy, respectively. Moreover, surface relaxation is accompanied by further amorphization in surface-near regions and a reduction in the mass density, as demonstrated by Raman spectroscopy and X-ray reflectivity. Since ion bombardment can be performed on global and local scales, it constitutes a versatile tool to achieve well-defined and tunable topographies and distinct surface characteristics. Hence, different types of nanotube arrays can be modified for various applications.

Conductive Tracks in Carbon Implanted Titania Nanotubes: Atomic‐Scale Insights from Experimentally Based Ab Initio Molecular Dynamics Modeling

“…An implantation‐caused increase in the number of C precipitates can be deduced from Raman spectroscopy as well. [ 16 ] As discussed in this study, a shift of the G peak indicates a transition from nanocrystalline graphite (presumably residues of the organic electrolyte of the production process) to graphite.…”

“…[ 34 ] Both these mechanisms contribute to viscous flow in the irradiated glassy system, as shown previously. [ 15,16,20 ] Especially at lower temperatures, viscous flow prevails as a manifestation of shear instabilities due to irradiation‐induced point defects, namely, shear transformation zones. [ 35,36 ] These effects of flow and enhanced diffusivity on the atomic level are imposed on the AIMD trajectories by increasing the canonical ensemble temperature to 3000 K. This regime is chosen, as it compares well with those temperatures obtained by previous studies on irradiation‐induced thermal spikes in amorphous TiO$$_2$$ on short time scales.…”

“…Crucial for this is controlling the depth profile of dissipated energy (either kinetic and/or stored in structural defects) by an interplay of ion energy, species, and fluence. [ 16 ]…”

“…The production of titania nanotubes and implantation has already been presented in different experimental sections, [ 16,20 ] and can additionally be found in the Supporting Information. In brief, the titania nanotubes of $$\approx 1\,\mathrm{\mu m}$$ height on a 0.1 mm thick Ti foil, were produced by electrochemical anodization.…”

“…[9][10][11][12] Among those, ion implantation is showing promise as a tool for precisely DOI: 10.1002/adts.202200063 tailoring structural and electronic properties. [13][14][15][16] This also includes nanoscale chainlike compositional patterning, which arises upon carbon ion implantation and will be in the center of focus of the present manuscript.…”