Creation of surface nanostructures in lanthanum fluoride single crystals by irradiation with slow highly charged ions

摘要

Slow highly charged ions (HCI) were utilized successfully for the formation of various nanostructures in the surfaces of different materials. The creation mechanism of HCI-induced nanostructures was intensively studied in alkali- and alkaline-earth fluorides. Here, we are investigating another type of fluorine-containing ionic crystals of different crystalline and electronic structure, namely lanthanum fluoride, LaF_3. The single crystals were irradiated with slow (eV-keV) highly charged xenon ions from an Electron Beam Ion Trap. After irradiation, the crystals surfaces were investigated by scanning force microscopy. The measured topographic images show nanohillocks emerging from the surface. These nanostructures were observed only after exceeding a well-defined threshold in the potential energy. The role of ion parameters for nanohillocks formation as well as a comparison with results for swift heavy ion irradiations of LaF_3 single crystals are presented. Furthermore, the similarities and differences between LaF_3 and other ionic fluoride crystals, in the creation of surface nanostructures, are discussed.