Dynamic Effects in Voltage Pulsed Atom Probe

Abstract

Abstract

Understanding the Nature of Crystallographic Bonds by Establishing the Correlation between Ion-Pair Chemistry and Their Separation in Detector Space

“…Products of molecular dissociation are subjected to Coulomb repulsion, which can affect the ion trajectories (Muller et al, 2011; Blum et al, 2016). Additionally, the relative change in mass for the individual dissociation products will influence their ion trajectories (Rousseau et al, 2020). The bimodal trend observed in Al-N 2 + was not apparent in the single-nitride (14 Da) Al-N + pairs, suggesting a unique chemical dissociation path for evaporation of Al-N 2 + molecules.…”

“…It is believed that the multi-hit events are mainly associated with potential errors in compositional accuracy resulting from preferential signal loss (Thuvander et al, 2013; Meisenkothen et al, 2015; Peng et al, 2018; Engberg et al, 2019; Cuduvally et al, 2020); however, statistical analysis of ion pairs within multi-hit detector events can yield significant information relating to the compositional biases (Saxey, 2011; Rousseau et al, 2020; Schwarz et al, 2020). Licata et al found that the percentage of multi-hit events increases with increased Al concentration (Al x Ga 1− x N from x = 0 to 1.0), suggesting that the relative field evaporation required for single Al and N ions is higher than the field required to evaporate AlN pairs and that, conversely, the field required to evaporate single Ga and N ions is less than GaN pairs (Licata et al, 2020).…”

Three-Dimensional Atomically Resolved Analytical Imaging with a Field Ion Microscope

“…This artifact will also be present in our LEAP 5000XS machine where non-correlated evaporation is taking place and it would occur in a voltage-pulsed APT experiment. In contrast to normal APT operation, they were evident in our experiments because of the abundance of light imaging gases (Rousseau et al, 2020) and because we kept the standing voltage constant, prevented this artifact being smeared. One obvious solution would be to employ laser pulsing in our future aFIM experiments until this issue can be resolved.…”

“…This was seenthere was one cluster at (1,20) representing the (H + /Ne + ) co-evaporation and another cluster at (4,20) representing the (He + /Ne + ) co-evaporation. The artefact and its phenomena at (4,20), has been explained recently (Rousseau et al, 2020) and the ripples can be thought of as a continuation. Away from these points, the curving lines passing through these points are generally shifted to larger masses because they evaporate at a lower voltage and so attain less energy.…”

“…For example, the signal pertaining to correlated tungsten-hydrogen evaporation in Figure 5(a) was low, but the corresponding inter-impact distance for this co-evaporation was larger than for tungsten-neon or tungsten-tungsten evaporation. This may be related to the mass of the ion and the effects of dynamic effects from the pulse (Rousseau et al, 2020). Other metrics may provide different filtering options, not only upon multiple detection events, but also ions detected on successive pulses for instance (De Geuser et al, 2007).…”