Mass resolution enhancement in local-electrode atom probes: A preliminary study using field emitter arrays

The use of post-evaporation acceleration as a means to enhance mass resolution in local-electrode atom probes (LEAP) is experimentally investigated in this study. Gated silicon field emitter arrays which have an extraction electrode-tip structure similar to a LEAP are used to evaporate ions at low voltages which are then accelerated to higher voltages. The study confirms the expected improvement in mass resolution. The mass resolution achieved using this gated field emitter array is however quite poor owing to capacitive coupling between the extraction electrode and the tip which leads to a broadened evaporation pulse. An improved model to relate time-of-flight to ion mass-to-charge ratio is found to be necessary in this atom probe configuration. These findings suggest important design considerations for extraction electrodes for a LEAP.