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Abstract: Sputtering occurs as a result of deposition of kinetic or potential energy in solids irradiated with swift particles. We studied ejection of secondary ions from LiF induced by swift heavy ion impact. A new UHV system allows measuring the mass distributions and the velocity vectors of each emitted secondary ion by means of time-of-flight and imaging techniques (XY-TOF-SIMS) with controlled target surfaces. We present results performed at GANIL (Caen) with Ca beams at 7.6 and 9MeV/u (electronic stopping regime). Under UHV conditions, particles emitted from cleaved LiF monocrystals include the omnipresent hydrogen, and the two isotopes of natural LiF (6Li+ and 7Li+). Two groups of clusters, namely and (LiF) n Li+ appear. The cluster size (n) dependence of the cluster ion yields Y(n) can be described by an exponential function. LiF emission as ionic clusters (LiF) n Li+ with n ⩾2 is dominant over emission as monomers LiFLi+. [Copyright &y& Elsevier]

Abstract: The accelerator facilities of GANIL allow studying ion–surface collisions in a wide range of projectile velocities. On the one hand, high velocity heavy ions (MeV/u) where the electronic energy loss is dominant (electronic sputtering), and on the other hand, low velocity highly charged ions (keV/q) are available. In the latter case, nuclear stopping (elastic collision cascades) is more important. Possibly, further effects related to the high projectile charge and corresponding high potential energy can occur (potential sputtering). We use a combination of imaging techniques (XY) and time-of-flight (TOF) spectroscopy to measure the complete velocity vector of emitted secondary ions. We present results on energy and angular distributions of 7Li+ (atomic ions) sputtered from a LiF crystal by Ca17+ (9MeV/u) and Xe21+ (17keV/q =350keV) ions. The energy distributions differ strongly thus clearly showing that the material responds differently to energy deposition by purely electronic stopping (high velocity projectiles) and slow highly charged ions. We also compare the angular distributions of emitted Li+ ions and neutrals in the electronic stopping regime. [Copyright &y& Elsevier]

Abstract: In order to study the sputtering of secondary ions from well characterized surfaces, we constructed a new UHV system named AODO. It consists of a detector chamber, a target preparation and analysis chamber, and a target transfer rod. We present the lay-out of this new instrument. The detector allows measuring the time-of-flight of emitted secondary ions and their position on a 2D imaging detector (XY-TOF imaging technique). The analysis chamber can be used to study surface modification by means of LEED (low energy electron diffraction). We show preliminary results of the evolution of the LEED patterns as a function of the projectile fluence during irradiation of HOPG (highly oriented pyrolytic graphite) with slow Xe14+ ions at ARIBE (the low energy, highly charged ion beam line of the French heavy ion accelerator GANIL). [Copyright &y& Elsevier]