Atom probe determination of the multicomponent material thermo-field microprotrusion parameters

A time of flight atom probe has been used for investigation of some alloy thermo-field microprotrusions. The microprotrusions from HfMo (7 at. % Hf), HfW (3 at. % Hf), and IrRh (26 at. % Ir) alloys have been formed on the tip surface by simultaneous action of high temperature T and high electric field F. Conditions of forming, reproducibility of growth, location, emission properties, and chemical composition of the microprotrusions have been carefully studied. The peculiarities of field evaporation of the microprotrusions both at room temperature and at elevated temperature have also been investigated. Appreciable segregation of Rh and Hf on the surface of the alloys has been discovered. The thermo-field microprotrusions consist mainly of these surface components. Point ion and electron sources controlled by changing of T and F can be created on the basis of these microprotrusions. (C) 1997 American Vacuum Society.