FORMATION OF METAL HYDRIDE IONS IN LOW-TEMPERATURE FIELD EVAPORATION

When low-temperature field evaporation of metals is carried out in the presence of a small amount of hydrogen in the system, metal hydride i on species of multiple hydrogen atoms are usually formed. For most met als, the presence of a small amount of hydrogen in the system also red uces considerably the evaporation fields. The number of hydride specie s formed varies with metals. The questions we ask include: how many of the observed hydride ion species are really formed right at the surfa ce? How many of them are formed by field dissociation of these hydride ions? How does the field affect the field dissociation? These questio ns have not been systematically studied before. Here, we report such a study using a high-resolution pulsed laser time-of-flight atom-probe field ion microscope. (C) 1998 Elsevier Science B.V. All rights reserv ed.