Thermal spike model interpretation of sputtering yield data for Bi thin films irradiated by MeV 84Kr15+ ions

Sputtering of bismuth thin films under MeV Cu heavy ion irradiation: Experimental data and inelastic thermal spike model interpretation.

“…In the present case of Bi thin films irradiated by 26‐MeV Cu 7+ ions, the observed sputtering yield trend versus ion fluence is also similar to that we have prev2iously reported for the same target material but irradiated either by 27.5‐MeV Kr 15+ ions 11 or by 60 and 120‐keV Ar + ions . Such a close dependence of the sputtering yield on ion fluence was ascribed to the Bi target material nature (ie, thin film) and to the changes induced by ion irradiation in its surface topography and crystalline structure at a microscopic level . For keV Ar + incident ions, an important sputtering yield depression at very‐low ϕ‐values followed by a steady‐state regime above 2 × 10 14 cm −2 was observed in quantitative agreement with those shown in Figure of the present study.…”

“…For keV Ar + incident ions, an important sputtering yield depression at very‐low ϕ‐values followed by a steady‐state regime above 2 × 10 14 cm −2 was observed in quantitative agreement with those shown in Figure of the present study. Then, by using 2 other analysis techniques of atomic force microscopy and X‐rays diffraction, drastic surface topography and microstructure changes were observed when increasing both the Ar + ion energy and fluence with the formation of increasingly sized grains and granular structures of preferred (001) crystalline orientations . These correlated behaviors were explained due to the initial rapid erosion of a bulk‐character Bi material under the impact of primary Ar + ions before the sputtering yield saturation regime is reached, for which a much smaller energy density is deposited than initially at very thin thickness of the Bi film.…”

“…These effects were likely related to interaction mechanisms prevailing within the nuclear collision cascade regime like, eg, surface Bi recoil displacements following Ar + primary ion irradiation. Other additional mechanisms involving inelastic electronic collisions were also expected to increasingly contribute to the induced surface effects in Bi thin films over the explored incident energy range, where the nuclear and electronic energy losses have comparable magnitudes. While for MeV Kr 15+ incident ions, a close correlation was well established between the variations versus ion fluence of several Bi surface effects: (1) the measured sputtering yield decreased (up to ~ 9.1 × 10 12 cm −2 ) towards a steady‐state regime as the ion fluence increases, (2) the observed grain growth on the irradiated Bi sample surface with the increasing crystalline alignment towards the (001) crystalline structure and finally, (3) the decrease of the compressive crystalline strain induced defects when increasing ion fluence with a similar behavior to that of the measured sputtering yield .…”

“…Recently, we reported a careful experimental investigation of the sputtering and surface topography modifications suffered by Bi thin films deposited onto Si substrates under normal impacts of 27.5‐MeV 84 Kr 15+ ions . The obtained experimental data were first discussed in the framework of Sigmund's collision cascades transport theory before being compared with moderate surface effects from other previous work on similar Bi thin films irradiated by keV Ar + ions . Subsequently, in another supplementary contribution, we interpreted the measured Bi sputtering data in terms of a modified thermal spike model initially proposed by Yasui to account for defect formation in metals within the high energy regime.…”

Surface, structural and tensile properties of proton beam irradiated zirconium

“…The coulomb explosion and thermal spikes models describe the proton irradiation induced changes inside the Zr matrix. The Coulomb explosion model is valid in the initial stages of the radiation damage where the radiation damage is dominated by the production of vacancies and interstitial related defects inside the Zr [26], whereas the thermal spikes model explains the production of thermal stresses as a result of heat generation due inelastic collisions of protons with the Zr matrix [27][28][29]. During inelastic collisions, latent tracks of the excited electrons are generated which heat up the Zr lattice through electron-phonon coupling which causes a rise in the temperature of the Zr lattice [30,31].…”