Isotope analysis in the transmission electron microscope

TL;DR

This paper introduces a method to distinguish isotopes at atomic resolution in a transmission electron microscope by analyzing atom ejection probabilities, enabling precise isotope mapping in materials.

Contribution

The study develops a quantum mechanical model combined with DFT simulations to differentiate isotopes via atom ejection probabilities in electron microscopy.

Findings

Successfully differentiated $^{12}$C and $^{13}$C in graphene.

Achieved isotope concentration mapping with better than 20% spatial resolution.

Method applicable to various atomic resolution transmission electron microscopes.

Abstract

The {\AA}ngstr\"om-sized probe of the scanning transmission electron microscope can visualize and collect spectra from single atoms. This can unambiguously resolve the chemical structure of materials, but not their isotopic composition. Here we differentiate between two isotopes of the same element by quantifying how likely the energetic imaging electrons are to eject atoms. First, we measure the displacement probability in graphene grown from either $^{12}$C or $^{13}$C and describe the process using a quantum mechanical model of lattice vibrations coupled with density functional theory simulations. We then test our spatial resolution in a mixed sample by ejecting individual atoms from nanoscale areas spanning an interface region that is far from atomically sharp, mapping the isotope concentration with a precision better than 20%. Although we use a scanning instrument, our method should be applicable to any atomic resolution transmission electron microscope and to other low-dimensional materials.