Depth profiling studies of multilayer films with a C60þ ion source

A newly developed C60þ 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 C60þ ion beam is used in the dcmode to sputter the surface for depth profiling while spectra are taken both with Gaþ 15 keV and C60þ 20 keV projectiles between sputtering cycles. From C60þ 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 ¼ 208:9 was monitored as a function of C60þ 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 nm of Cr on Si(1 0 0) at a C60þ 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 C60þ for depth profiling studies of multilayer targets. # 2004 Elsevier B.V. All rights reserved