Stopping power of He, C and O in TiO2

Stopping powers play a fundamental role in Ion Beam Analysis, because they are essential for the depth profiling capability of Rutherford backscattering and elastic recoil detection analysis, and also the depth range probed by other techniques such as particle induced X-ray emission. Any inaccuracy in the stopping powers are directly reflected in the depth scales determined. In practice, IBA relies on data bases or interpolative schemes such as SRIM or MSTAR, which depend on existing data. For compounds and for heavy ions, the data bases are scarce, and inaccuracies can be large. Titanium dioxide is a semiconductor used in photocatalytic thin films and as a UV absorber material. Light dopants and impurities change its properties and heavy ion ERDA is an ideal technique to study them. However, to our knowledge no measurements have yet been made of the stopping power of heavy ions in TiO2. We used a bulk method, previously developed by us and applied successfully to other systems, to determine experimentally the stopping power of 4He, 12C and 16O in TiO2 thin films grown on glassy carbon, in the energy ranges 0.1-2.4, 0.6-9.9, and 0.3-14.9 MeV, respectively. The results of our measurements are presented.