Secondary ion mass spectrometry with C60+ and Au4004+ projectiles: Depth and nature of secondary ion emission from multilayer assemblies

Alternating nanometric thin layer films made from poly(diallyldimethylammonium chloride), poly(styrene sulfonate) and montmorillonite clay were analyzed with 26 keV C60+ (433 eV/atom) and 136 keV Au4004+ (340 eV/atom). Secondary ion (SI) emission depth from such thin films was determined to be ∼6–9 nm with C60+ bombardment. Similar depth of emission was also reported with Au4004+ projectile impacts [Z. Li, S.V. Verkhoturov, E.A. Schweikert, Anal. Chem. 78 (2006) 7410]. The SI spectra contain recoiled C60 projectile constituents (m/z = 12, 13, 36). They track the compositional variation of the assembled thin layers except for C− and CH− whose abundances appear to correlate with the presence of metal atoms in the topmost layer.