High-resolution elastic recoil depth profiling using alpha-particle beams:CERDA-TOF

An improved coincidence time-of-flight recoil spectrometer is described. The use of alpha-particles instead of heavy ions to eject the recoils has the advantages of larger depth range and smaller target damage. Multi-element analysis and element-selective depth profiling on thin and moderately thick targets are demonstrated. A surface depth resolution of 3 nm has been obtained for 12C in carbon at a recoil angle φ of 30°. Resolution down to 1 nm is predicted when further compensation of kinematic effects is realized; using very well defined beams it might be possible to obtain atomic layer resolution. Strategies to extend the present sensitivity of about 1014 atoms cm2 by one or two orders of magnitude are discussed.