Three-dimensional atomically-resolved analytical imaging with a field ion microscope

TL;DR

This paper introduces a hybrid analytical field ion microscopy (aFIM) technique combining FIM and APT to achieve atomic resolution with elemental discrimination, overcoming limitations of each method alone.

Contribution

The authors demonstrate a novel hybrid approach using existing instruments to attain atomic resolution and elemental identification simultaneously, a significant advancement over traditional methods.

Findings

Successful acquisition of time-of-flight mass spectrometry data during FIM experiments.

Development of data mining strategies for discriminating ion signals from background noise.

Discussion of experimental challenges in detecting and identifying individual ions.

Abstract

Atom probe tomography (APT) helps elucidate the link between the nanoscale chemical variations and physical properties, but it has limited structural resolution. Field ion microscopy (FIM), a predecessor technique to APT, is capable of attaining atomic resolution along certain sets of crystallographic planes albeit at the expense of elemental identification. We demonstrate how two commercially-available atom probe instruments, one with a straight flight path and one fitted with a reflectron-lens, can be used to acquire time-of-flight mass spectrometry data concomitant with a FIM experiment. We outline various experimental protocols making use of temporal and spatial correlations to best discriminate field evaporated signals from the large field ionised background signal, demonstrating an unsophisticated yet efficient data mining strategy to provide this discrimination. We discuss the remaining experimental challenges that need be addressed, notably concerned with accurate detection and identification of individual field evaporated ions contained within the high field ionised flux that contributes to a FIM image. Our hybrid experimental approach can, in principle, exhibit true atomic resolution with elemental discrimination capabilities, neither of which atom probe nor field ion microscopy can individually fully deliver - thereby making this new approach, here broadly termed analytical field ion microscope (aFIM), unique.