Depth profiling studies of multilayer films with a C60+ ion source

A newly developed C-60(+) primary ion beam source for time-of-flight secondary ion mass spectrometry has been employed for depth profiling analysis of organic and inorganic multilayer films. In particular, the C-60(+) ion beam is used in the dc mode to sputter the surface for depth profiling while spectra are taken both with Ga+ 15 keV and C-60(+) 20 keV projectiles between sputtering cycles. From C-60(+) bombardment of Langmuir-Blodgett films of barium arachidate, we find that cluster beams increase the secondary ion yields and ion formation efficiencies compared to monoatomic projectiles. For a 15-layer film, a barium arachidate fragment ion at m/z = 208.9 was monitored as a function Of C-60(+) dose to determine that the sputtering rate is about 1.54 nm/s and that the film interface position can be determined with a depth resolution of 16 nm. For comparison purposes, a depth resolution of 8.7 nm was measured for a sample consisting of 66 nm of Ni and 53 nrn of Cr on Si(100) at a C-60(+) beam energy of 20 keV. The neutral atom yield was monitored via laser postionization to avoid matrix effects. These experiments show great promise for the use Of C60+ for depth profiling studies of multilayer targets. (C) 2004 Elsevier B.V. All rights reserved.