ERD analysis and modification of TiO2 thin films with heavy ions

Titanium dioxide (TiO2) films have been deposited on Si substrates using reactive magnetron sputtering. The resulting films, having a polycrystalline anatase phase with a dense columnar structure, were analysed by time-of-flight elastic recoil detection analysis (ToF-ERDA) using 40 MeV I9+ ions. A clear decrease in the areal atomic density (atoms/cm2) of Ti and O was observed during measurement, but the stoichiometry remained essentially constant up to a fluence of 4 x 1013 ions/cm2. To investigate this effect in more detail, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were applied in order to characterize the films prior to and after ion irradiation with fluences in the range of 1010-1013 ions/cm2. Distinct morphological and structural changes of the polycrystalline film were observed. XRD revealed that the crystallinity of the film was gradually destroyed, and the film became amorphous at a fluence above 5 x 1012 ions/cm2. SEM and AFM measurements revealed topographical changes in the form of surface recession and smoothing compared to the pristine polycrystalline surface. The observed change in areal atomic density during ERD measurement is believed to be due to the combined effects of electronic sputtering, amorphization and ion hammering.