Nanoscale 3D tomography by in-flight fluorescence spectroscopy of atoms sputtered by a focused ion beam

TL;DR

This paper introduces FIB-induced fluorescence spectroscopy (FIB-FS), a high-resolution, high-sensitivity 3D nanoscale technique for atom detection and tomography during focused ion beam processing, applicable to all elements and real-time analysis.

Contribution

The paper presents FIB-FS as a novel method combining FIB nanofabrication with fluorescence spectroscopy for 3D nanoscale atom detection and tomography.

Findings

Demonstrated nanoscale lateral and depth resolution limited by ion-induced intermixing.

Qualitative depth-profiling of quantum wells at nanometer scale.

Quantitative detection of trace impurities at parts-per-million levels.

Abstract

Nanoscale fabrication and characterisation techniques critically underpin a vast range of fields, including materials science, nanoelectronics and nanobiotechnology. Focused ion beam (FIB) techniques are particularly appealing due to their high spatial resolution and widespread use for processing of nanostructured materials and devices. Here, we introduce FIB-induced fluorescence spectroscopy (FIB-FS) as a nanoscale technique for spectroscopic detection of atoms sputtered by an ion beam. We use semiconductor heterostructures to demonstrate nanoscale lateral and depth resolution and show that it is limited by ion-induced intermixing of nanostructured materials. Sensitivity is demonstrated qualitatively by depth-profiling of 3.5, 5 and 8 nm quantum wells, and quantitatively by detection of trace-level impurities present at parts-per-million levels. To showcase the utility of the FIB-FS technique, we use it to characterise quantum wells and Li-ion batteries. Our work introduces FIB-FS as a high-resolution, high sensitivity, 3D analysis and tomography technique that combines the versatility of FIB nanofabrication techniques with the power of diffraction-unlimited fluorescence spectroscopy. It is applicable to all elements in the periodic table, and enables real-time analysis during direct-write nanofabrication by focused ion beams.