Time-Resolved Focused Ion Beam Microscopy: Modeling, Estimation Methods, and Analyses

TL;DR

This paper develops a theoretical framework and novel estimators for time-resolved focused ion beam microscopy, demonstrating significant improvements in image quality by mitigating shot noise through multiple measurements.

Contribution

It introduces idealized measurement models and estimators for FIB microscopy, analyzing their performance and showing how increased time resolution enhances imaging quality.

Findings

Estimators approach continuous-time performance as resolution increases

Simulations confirm theoretical improvements in image quality

Time-resolved measurements reduce shot noise effects

Abstract

In a focused ion beam (FIB) microscope, source particles interact with a small volume of a sample to generate secondary electrons that are detected, pixel by pixel, to produce a micrograph. Randomness of the number of incident particles causes excess variation in the micrograph, beyond the variation in the underlying particle-sample interaction. We recently demonstrated that joint processing of multiple time-resolved measurements from a single pixel can mitigate this effect of source shot noise in helium ion microscopy. This paper is focused on establishing a rigorous framework for understanding the potential for this approach. It introduces idealized continuous- and discrete-time abstractions of FIB microscopy with direct electron detection and estimation-theoretic limits of imaging performance under these measurement models. Novel estimators for use with continuous-time measurements are introduced and analyzed, and estimators for use with discrete-time measurements are analyzed and shown to approach their continuous-time counterparts as time resolution is increased. Simulated FIB microscopy results are consistent with theoretical analyses and demonstrate that substantial improvements over conventional FIB microscopy image formation are made possible by time-resolved measurement.