Formation of swift heavy ion tracks on a rutile TiO2 (001) surface.

Marko Karlušić,Maja Buljan,Sigrid Bernstorff,Ivančica Bogdanović-Radović,Marika Schleberger,Branko Šantić,Zdravko Siketić,Milko Jakšić

doi:10.1107/s1600576716013704

Abstract

Nanostructuring of surfaces and two-dimensional materials using swift heavy ions offers some unique possibilities owing to the deposition of a large amount of energy localized within a nanoscale volume surrounding the ion trajectory. To fully exploit this feature, the morphology of nanostructures formed after ion impact has to be known in detail. In the present work the response of a rutile TiO2 (001) surface to grazing-incidence swift heavy ion irradiation is investigated. Surface ion tracks with the well known intermittent inner structure were successfully produced using 23 MeV I ions. Samples irradiated with different ion fluences were investigated using atomic force microscopy and grazing-incidence small-angle X-ray scattering. With these two complementary approaches, a detailed description of the swift heavy ion impact sites, i.e. the ion tracks on the surface, can be obtained even for the case of multiple ion track overlap. In addition to the structural investigation of surface ion tracks, the change in stoichiometry of the rutile TiO2 (001) surface during swift heavy ion irradiation was monitored using in situ time-of-flight elastic recoil detection analysis, and a preferential loss of oxygen was found.

Highlights

Swift heavy ions (SHIs) have found widespread use in research and technology, for both materials analysis and modification
While the manipulation of ion tracks remains the basis for numerous applications like the production of track etched membranes or ion beam lithography, intact ion tracks offer the opportunity to study the basic mechanisms of SHI–matter interaction (Itoh et al, 2009; Aumayr et al, 2011; Toulemonde et al, 2012)
The advantages of small-angle X-ray scattering (SAXS) over other techniques are numerous: it does not require single-crystal samples like Rutherford backscattering spectroscopy (RBS/c), it can be used to study radiation-sensitive materials like LiF which are very difficult to analyse with transmission electron microscopy (TEM), and it can resolve very small differences in the density between ion tracks and the surrounding matrix, as the scattered intensity is proportional to the electron density difference between them

Summary

Introduction

Swift heavy ions (SHIs) have found widespread use in research and technology, for both materials analysis and modification. Different energy dissipation channels like emission of secondary electrons or sputtering can be used to monitor SHI interaction processes with surfaces, atomic force microscopy (AFM) constitutes the most widely used technique to investigate nanostructures at the surface after exposure to SHI beams (Aumayr et al, 2011) This approach allows a detailed investigation of ion track morphology, but obtaining reliable statistical information remains a time-consuming process owing to the low data accumulation speed of scanning probe methods. The advantages of SAXS over other techniques are numerous: it does not require single-crystal samples like RBS/c, it can be used to study radiation-sensitive materials like LiF which are very difficult to analyse with TEM, and it can resolve very small differences in the density between ion tracks and the surrounding matrix, as the scattered intensity is proportional to the electron density difference between them This last point makes SAXS a perfect tool for the investigation of ion tracks in amorphous materials. We used time-of-flight elastic recoil detection analysis (TOF-ERDA) to monitor possible stoichiometric changes of the rutile phase during the SHI irradiation

Experimental

Results and discussion

Conclusion