Some aspects of the field evaporation behaviour of GaSb

In-depth analysis of pulsed laser atom probe tomography (APT) data on the field evaporation of the III–V semiconductor material GaSb reveals strong variations in charge states, relative abundances of different cluster ions, multiplicity of detector events and spatial correlation of evaporation events, as a function of the effective electric field at the specimen surface. These variations are discussed in comparison with the behaviour of two different metallic specimen materials, an Al-6XXX series alloy and pure W, studied under closely related experimental conditions in the same atom probe instrument. It is proposed that the complex behaviour of GaSb originates from a combination of spatially correlated evaporation events and the subsequent field induced dissociation of cluster ions, the latter contributing to inaccuracies in the overall atom probe composition determination for this material.

Research Highlights
► Atom probe microanalysis of GaSb shows a variety of cluster ions depending on the analysis conditions.
► Cluster ions can be dissociated by a mechanism that involves the intense electric field in the vicinity of the specimen surface.
► In-depth analysis of the spatial and time correlations of multiple events provides insight into the mechanisms leading to the formation and dissociation of such clusters and their fragmentation route.
► Dissociation processes induce very high proportion of multiple events which is likely to impact upon the chemical accuracy of atom probe microanalysis.