Stopping power and energy loss straggling data of Bismuth thin film for (0.9–3.0) MeV 4He+ swift ions

Highlights: • Energy loss and energy straggling were measured for (0.9–3.0) MeV He⁺ ions in Bismuth thin films. • RBS analysis was used to derive energy dependence of stopping power and energy straggling. • The obtained results were compared to different predicted stopping and straggling models. -- Abstract: Stopping power and energy loss straggling data of ⁴He⁺ swift ions in Bismuth thin film (Bi/Si) deposited onto silicon substrate were measured via Rutherford backscattering spectrometry (RBS) at incident energies ranging from 0.9 to 3.0 MeV. We adopted an improved experimental method based on the Kr⁺ ion implantation of the target Si substrate at low 40 keV energy and using the generated Kr-peak in the backscattered RBS spectra as reference to extract both the energy loss and the energy loss straggling for He⁺ ions crossing the Bi thin film. The obtained experimental stopping power values were found in good agreement with those generated numerically via SRIM-2013 and CasP 5.2 computer codes. They are also showed to be consistent with previously reported stopping data within the He⁺ ion energy region mainly below 1.5 MeV, which are thus extended them to higher incident energies. Finally, the relevance of collisional straggling values predicted by Bohr's and Bethe-Livingston's theories for describing the determined experimental straggling data was discussed by invoking two main additional contribution effects due to target thickness inhomogeneity and ion charge exchanges included in the Yang semi-empirical formula.