The interaction of Bi cluster ions with molecular compounds : towards a new generation of organic time of flight secondary ion mass spectrometry

Abstract

The fundamental capability of Bi_x primary ions for the investigation and analysis of organic compounds has been demonstrated by means of static secondary ion mass spectrometry. The detailed processes of ion formation and the signal enhancement of distinctive molecular fragments will be employed as basic principles for the individual assignment of polymers, amino acids and alkane-like self assembled mono- layers. Furthermore, it has been proven that the peculiarities of these mono-atomic and poly-atomic primary ions are likely to influence the ion formation and fragmentation to a certain degree. For the first time, such cluster-ion based measurements have been applied to a modified approach of data refinement derived from the well-established g-SIMS procedure. Based on mass spectra, which correspond to different primary ion species, not only a clear distinction between the substances is practicable, but also a further simplification of the data can be demonstrated. It has been successfully proven that characteristic signals can be refined out of the large amount of unspecific and highly fragmented secondary ions, which are usually present in SIMS spectra. Whereas it is feasible to reduce the mass spectra of lysine and phenylalanine to one single signal that can be associated with the native molecular structure of the amino acids, polymers like poly(4- vinylphenol) and poly(methyl methacrylate) are slightly more demanding. Instead of a single cluster ion based g-SIMS algorithm, the primary ions Bi and Mn will be allocated as suitable combination for the investigation of these polymer samples. Nevertheless, a more precise and direct interpretation of complex organic materials becomes conceivable by this novel approach, which consequently enables the investigation of even more complex samples.