Heliometric stereo: a new frontier in surface profilometry

TL;DR

This paper introduces heliometric stereo for scanning helium microscopy, enabling quantitative 3D surface topography measurements with high accuracy, and discusses its implementations, limitations, and potential applications in surface profilometry.

Contribution

The paper presents two implementations of heliometric stereo in SHeM, demonstrating quantitative 3D surface mapping and analyzing factors affecting accuracy.

Findings

Achieved 5% and 10% accuracy in surface shape recovery

Demonstrated two different heliometric stereo implementations

Identified contrast features affecting measurement accuracy

Abstract

Accurate and reliable measurements of three-dimensional surface structures are important for a broad range of technological and research applications, including materials science, nanotechnology, and biomedical research. Scanning helium microscopy (SHeM) uses low-energy (64 meV) neutral helium atoms as the imaging probe particles, providing a highly sensitive and delicate approach to measuring surface topography. To date, topographic SHeM measurements have been largely qualitative, but with the advent of the heliometric stereo method - a technique that combines multiple images to create a 3D representation of a surface - quantitative maps of surface topography may now be acquired with SHeM. Here, we present and discuss two different implementations of heliometric stereo on two separate instruments, a single detector SHeM and a multiple-detector SHeM. Both implementations show good accuracy (5% and 10% respectively) for recovering the shape of a surface. Additionally, we discuss where heliometric stereo is most applicable, identify contrast features that can limit its accuracy, and discuss how to mitigate these limitations with careful design and sample choices that be readily implemented on current instruments.