A trial scanning atom probe and field distribution at a tip apex of a micro-tip array

Abstract

Summary form only given, as follows. A trial scanning atom probe (SAP) was constructed by modifying a low temperature UHV scanning tunneling microscope (STM). The specimen holder of the conventional STM was replaced with a holder of an extraction electrode made of a 10 micrometer thick Pt foil. The specimen micro-tip array is mounted at one end of a piezo tube which allows one to move the specimen with subnanometer precision. Silver foils connecting the cold end of the cryogenic refrigerator and the holder of the piezo tube cool the specimen and piezo assembly down to 50 K. Field emitted electrons and field ionized gas ions project images of an individual tip apex of a micro-tip array at atomic resolution and field evaporated apex atoms fly into the flight space of a reflectron mass analyzer through the probe hole at the center of the screen. The results of preliminary experiments are reported. While constructing the SAP, the field distributions around the tip apex were computed in order to examine the variation of field emitted current with the relative position of the tip apex and the open hole of the extraction electrode. The calculated field distribution is presented, comparing the observed variation of emitted current with the relative positions.