High‐spatial‐resolution surface imaging of inorganic and organic structures by multiphoton post‐ionization of sputtered neutrals and time‐of‐flight mass spectrometry

Non-resonant multiphoton ionization (NRMPI) of sputtered atoms as well as resonance-enhanced multiphoton ionization (REMPI) of sputtered organic molecules in combination with time-of-flight mass spectrometry has turned out to be one of the most sensitive techniques for surface analysis. If, additionally, high spatial resolution is demanded the ionization process has to be extremely efficient since only a very limited amount of sample material is available. In preliminary investigations we used ultrashort and intense UV laser pulses (500 fs pulse width) for both elemental and molecular surface imaging. Images of an Ag-coated Cu grid, an Au-pattern on Si and surface structures of a biomolecule (tryptophan) and a polymer (polystyrene) are presented. Useful yields of up to 1% are achieved.