Some aspects of the field evaporation behaviour of GaSb

Abstract

Molecular or cluster ions are often observed in the atom probe microanalysis of III-V compound semiconductors. Here, in-depth data analysis of a series of experiments on GaSb reveals strong variations in the mass spectrum, cluster ion appearance and multiplicity of the detector-events with respect to the effective electric field at the specimen surface. These variations are discussed in comparison with Al 6XXX series alloys and pure W and it is proposed that they may originate from field-dissociation of molecular ions, which might contribute to compositional inaccuracies. Abstract 2

Characterization of ion-irradiation-induced nanodot structures on InP surfaces by atom probe tomography

“…The relative fraction of these P n cluster was found to depend quite distinctly on the laser pulse energy (see below). Although cluster emission has been found before in APT of III-V [37][38][39][40][41] and other compound semiconductors [42], InP appears to constitute an extreme case in that respect. The formation and emission of such (large) clusters seems to indicate that P atoms migrate across the tip surface and may, eventually, agglomerate into clusters; these newly-formed moieties can then leave the tip by field evaporation.…”

Effects of detector dead-time on quantitative analyses involving boron and multi-hit detection events in atom probe tomography

“…Recent studies on the behavior of the ions that comprise multi-hit events indicate that they are closely correlated in space and time [15,22,37,38], while ions uncorrelated with the pulse tend to be single-hit events that contribute to the background noise signal [15,38]. Hence, filtering techniques can be used to extract the ion information for the high-multiplicity events, and thereby provide a mass spectrum that has an improved signal-to-noise ratio [15].…”

“…For example, for multiplicity-2 events, the ion hit positions on the detector can be used to calculate the relative separation distance between the two ions in the pair [37,38]. The distribution of the separation distances at the detector between ions in multiplicity-2 events for the nominally pure B is illustrated in Figure 6 and for the SRM2137 materials in Figure 7.…”

Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

“…At low laser energies, the standing voltage in APT must be higher to compensate for a lack of thermal excitation, causing higher electric fields and potential field ion dissociation. Field dissociation has been previously noted in APT of ceramic materials [20,50] at low laser energies. This may explain why individual U n+ and O n+ type ions accompany the increase in UO n+ type ions.…”