Quantitative aspects of secondary ion mass spectrometry analysis of pure and mixed fatty acid Langmuir-Blodgett films

Polycrystalline silver supported pure and mixed mono- and multilayer films of eicosanoic [CH₃(CH₂)₁₈COOH] and docosanoic [CH₃(CH₂)₂₀COOH] acids have been prepared by the standard Langmuir-Blodgett technique. The emission of quasimoiecular ions as a function of ion dosage has been studied to infer information regarding secondary ion stability under ion bombardment. The results indicate molecular orientation and substrate dependence for (M + H)⁺ emission and the attenuation of (M + Ag)+ and (M — H + 2Ag)⁺ with increased film thickness. Data are presented for studies conducted on both quadrupole mass filter and time-of-flight instrumentation. The effects of supporting substrate morphology, instrumentation, and implications for quantification of molecular static-secondary ion mass spectrometry (static-SIMS) ion emission are discussed.