Experimental study and thermal spike modeling of sputtering in SiO₂ thin films under MeV Au^q+ heavy ion irradiation

Abstract

The sputtering of silicon dioxide (SiO2/Si) thin films deposited onto silicon substrates and irradiated by swift Auq+ heavy ions (q = +4 to +9) has been investigated both by experiment and via numerical modeling by varying the kinetic energy from 10 to 40 MeV. The induced sputtering yields were determined experimentally via the Rutherford backscattering spectrometry (RBS) technique using a 2‐MeV He+ ion beam. The obtained experimental results were first plotted versus the target electronic stopping power together with previous data available for the same projectile‐target system at high kinetic energies, indicating increased sputtering yields with increasing electronic energy loss. Then, the whole data were compared with numerical sputtering yield values derived both from the inelastic thermal spike model and the SRIM‐2013 simulation code by including, respectively, nonlinear elastic spikes and linear elastic collision cascades. A good agreement was observed between the measured sputtering yield data and i‐TS predicted values over higher incident energies used by using refined parameters of the ion slowing down with reduced thermophysical properties of the SiO2 thin film. Finally, the synergy between electronic and nuclear energy loss processes inducing sputtering at low incident energies was discussed through the comparison between experimental and numerical yield data.

Sputtering and structural modifications induced in silicon dioxide (SiO2) thin films under (10–40 MeV) Auq+heavy ion irradiation

“…Therefore and as a continuation to our previous work 26 on sputtering yield measurements in case of SiO 2 thin films under (20–40 MeV) Au q+ heavy ion irradiation, we report in this paper an exhaustive investigation on the correlation between the measured total and partial sputtering yields via two combined ion‐beam analysis techniques (RBS, ToF‐ERDA) and the structural modifications induced in these irradiated (SiO 2 /Si) samples by using an additional characterization technique of grazing‐incidence X‐rays diffraction (GIXRD) spectroscopy. This involves quantifying the induced changes of the surface state and microstructure of the SiO 2 irradiated samples in terms of grain growth and strain, and correlating them to the measured electronic sputtering yields via the two above analysis techniques.…”

“…The ion fluence was fixed to a mean value around ~5 × 10 14 cm −2 . We note here that the RBS analysis of the (SiO 2 /Si) samples was already carried out and the measured total sputtering yields versus electronic stopping power were previously published 26 and interpreted in the framework of the i‐TS model. The RBS analysis was completed in the present work by another ion‐beam technique using ToF‐ERDA with a 40 MeV Au 9+ incident ion beam.…”

“…As described previously, 26 the silicon dioxide (SiO 2 ) thin films with thicknesses of ~150 nm were deposited onto 1.0 cm 2 silicon substrates with Si(100) orientation using the electron beam evaporation technique (under high vacuum of ~5 × 10 −5 Pa ). Prior to deposition, the Si substrates were well cleaned with chemical solvents by removing all contaminants and native oxides, and then they were placed edge‐to‐edge in the evaporator chamber in order to obtain similar deposited film thicknesses.…”

“…The obtained sputtering and structural results are reported in the next section, where they are treated and compared with previous observations. A possible correlation between the observed surface effects and the sputtering yields is also discussed and interpreted in the framework of the i‐TS model calculation 8,9,26 …”

“…This involves quantifying the induced changes of the surface state and microstructure of the SiO 2 irradiated samples in terms of grain growth and strain, and correlating them to the measured electronic sputtering yields via the two above analysis techniques. The obtained results are interpreted using the i‐TS model 8,9,26 . The experimental procedure of deposition and irradiation of SiO 2 samples summarized in our previous paper 26 is briefly described here in Section 2 along with GIXRD and heavy ion ToF‐ERDA analysis techniques.…”