Observation of light and secondary ion emissions from surfaces irradiated with highly charged ions

Abstract

Visible light and secondary ions emitted from various sample surfaces (Si, HOPG, Cu, and Teflon) were observed after irradiation with highly charged ions (HCIs). HCIs were produced using an electron beam ion source (Kobe EBIS) at Kobe University. Visible emissions were detected using a liquid nitrogen cooled CCD detector. The mass spectrum of secondary ions was obtained using a quadrupole mass analyzer. The major constituent in both light and secondary ion emissions was hydrogen. Balmer lines were the dominant form of light emission as observed from spectra, and proton signals were the most intense peaks in SIMS spectra. The emission intensity of Balmer light and the proton signal intensity (as observed from the SIMS spectrum) both increased as the charge state of the incident HCI increased. Both intensities were roughly proportional to the third to fourth power of the charge state. Spatial distribution of Balmer light was measured and the kinetic energy of hydrogen sputtered from the surface was estimated to be ∼20 eV. The SIMS measurement results for the Teflon sample demonstrate the advantage of using SIMS with an HCI probe for detecting electronegative elements.