engleski

Etched ion track depth profile measurements using STIM

Scanning transmission ion microscopy (STIM) is a single ion technique developed for the imaging of thickness/density distributions in transmission samples at submicron levels. Spatial resolution of STIM generally has to be better than the smallest feature size of the sample under study. Etched ion tracks in materials like polymers and dielectrics are in majority of cases of sizes that are significantly below the ion microbeam spot size. As the structure and shape of ion tracks can not be studied at all by alternative techniques, we have tested possibility of STIM to be used as a characterization technique for such tracks. Simulations show that energy spectrum of transmitted ions and measurements under different angles can give sufficient information in order to characterize the full shape of the etched ion track. In addition large range of membrane thicknesses and aspect ratios of etched tracks can be studied by appropriate selection of ion type and its energy. In this work, cylindrical etched tracks in polycarbonate (commercial Whatman track etched membrane) and conical etched tracks in polyimide were investigated using proton and He ion beams of various energies. Studies of tracks that are comparable with dimensions of microbeam and also track that have diameters significantly below the microbeam size have been studied. Limitation of this technique due to microbeam profile was estimated on single pore depth profile. Influence of lateral and energy straggling on depth resolution were also investigated.

scanning transmission ion microscopy; STIM; etched ion track; depth profile

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