Kinetic and potential sputtering of an anorthite‐like glassy thin film

Abstract

In this paper, we present measurements of He+ and He+2 ion‐induced sputtering of an anorthite‐like thin film at a fixed solar wind‐relevant impact energy of ~0.5 keV/amu using a quartz crystal microbalance approach (QCM) for determination of total absolute sputtering yields. He+2 ions are the most abundant multicharged ions in the solar wind, and increased sputtering by these ions in comparison to equivelocity He+ ions is expected to have the biggest effect on the overall sputtering efficiency of solar wind impact on the Moon. Our measurements indicate an almost 70% increase of the sputtering yield for doubly charged incident He ions compared to that for same velocity He+ impact (14.6 amu/ion for He+2 vs. 8.7 amu/ion for He+). Using a selective sputtering model, the new QCM results presented here, together with previously published results for Ar+q ions and SRIM results for the relevant kinetic‐sputtering yields, the effect due to multicharged‐solar‐wind‐ion impact on local near‐surface modification of lunar anorthite‐like soil is explored. It is shown that the multicharged‐solar‐wind component leads to a more pronounced and significant differentiation of depleted and enriched surface elements as well as a shortening of the timescale over which such surface‐compositional modifications might occur in astrophysical settings. In addition, to validate previous and future determinations of multicharged‐ion‐induced sputtering enhancement for those cases where the QCM approach cannot be used, relative quadrupole mass spectrometry (QMS)‐based measurements are presented for the same anorthite‐like thin film as were investigated by QCM, and their suitability and limitations for charge state‐enhanced yield measurements are discussed.

Solar wind Helium ion interaction with Mg and Fe rich pyroxene as Mercury surface analogue

“…A detailed examination of the fluence dependence of He implantation however has not been conducted so far. More recent research focused on sputtering by solar wind ions and its contribution to exosphere formation [7][8][9].…”

Solar wind sputtering of wollastonite as a lunar analogue material – Comparisons between experiments and simulations

“…However, due to the comparably low sputtering yields of protons, the heavy ions, especially He, must not be neglected for solar wind sputtering (Barghouty et al, 2011;Hijazi et al, 2017;Hijazi et al, 2014). The upper surface of planets and moons mostly consists of O-rich minerals, a fact that leads to a combination of different sputtering effects.…”

Experimental Insights Into Space Weathering of Phobos: Laboratory Investigation of Sputtering by Atomic and Molecular Planetary Ions

“…The increase compared to only kinetic sputtering then reaches 1.43 in the steady state after prolonged ion bombardment, when normal incidence is considered (Szabo et al, 2020a). Similar sputtering yields are derived by Barghouty et al (2011) for the lunar analog KREEP and by Hijazi et al (2017) for anorthite. The fluence dependence of potential sputtering is caused by a decrease of the O content at the surface as the ions' potential energy only causes additional sputtering of O atoms.…”

“…QCM sputtering measurements have been performed by multiple research groups for the investigation of a wide range of space weathering effects, for example, Galli et al (2017Galli et al ( , 2018aGalli et al ( , 2018b investigated the sputtering of ice films under irradiation of different ion species as well as electrons. Potential sputtering yields by multiply charged He and Ar ions were obtained with thin films of anorthite (Hijazi et al, 2014(Hijazi et al, , 2017 and wollastonite (CaSiO 3 ) (Szabo et al, 2018(Szabo et al, , 2020a. Additionally, Biber et al (2020) analyzed the implantation behavior of solar wind He in pyroxene samples from the same deposition batch as the samples used in the present study.…”

“…Existing data on sputtering of planetary analog samples give “an uncertainty of roughly a factor of 2” in comparison to their used input values. However, the few existing experiments with analog samples focused on H + sputtering or the contribution by multiply charged solar wind ions (see e.g., Barghouty et al., 2011; Hijazi et al., 2017; Szabo et al., 2020a). Here additional potential sputtering effects will occur (Aumayr & Winter 2004).…”