Sputtering of uranium tetrafluoride in the electronic stopping region

Abstract

We have studied the sputtering of ²³⁵U from UF₄ surfaces by ions with energies in the electronic stopping region. The observed sputtering yields are very large and are associated with the electronic stopping power. Measured yields produced by ¹⁹F ions at energies ranging from 1/16 MeV/amu to 1½ Mev/amu exhibit a peak of S = 7.1 ± 1.5 for ¹⁹F⁺³ at an energy of ¼ MeV/amu. The data suggest that the yield depends on the charge state of the incident ion. The yields are independent of target temperature in the range between 70°C and 170°C. The energy spectrum of the neutral component of the sputtered particles produced by ¼ MeV/amu ¹⁹F⁺² has been measured with the mechanical time-of-flight spectrometer developed by Weller and Tombrello. The spectrometer data indicate that a large fraction of the sputtered particles is charged. We also describe the behavior of high energy sputtering of UF₄ by ⁴He, ¹⁶O and ²⁰Ne. Experiments with ¹⁶O and ²⁰Ne beams at 100 keV show that the Sigmund theory adequately describes the sputtering of UF₄ in the nuclear stopping region.