# Optical Nanoscopy of High-Tc Cuprate Nano-Constriction Devices Patterned by Helium Ion Beams

## TL;DR

This study demonstrates the use of combined AFM and SNOM techniques to achieve 3D dielectric characterization of high-Tc cuprate devices damaged by helium ion beam irradiation, revealing extensive amorphization.

## Contribution

It introduces AFM-SNOM as a novel, non-invasive method for 3D nano-scale damage assessment in irradiated superconductor devices.

## Key findings

- Amorphization extends throughout the entire 26.5 nm film thickness.
- Damage spreads laterally about 500 nm from the irradiation site.
- Helium depth distribution is significantly affected by internal interfaces.

## Abstract

Helium-ion beams (HIB) focused to sub-nanometer scales have emerged as powerful tools for high-resolution imaging as well as nano-scale lithography, ion milling or deposition. Quantifying irradiation effects is essential for reliable device fabrication but most of the depth profiling information is provided by computer simulations rather than experiment. Here, we use atomic force microscopy (AFM) combined with scanning near-field optical microscopy (SNOM) to provide three-dimensional (3D) dielectric characterization of high-temperature superconductor devices fabricated by HIB. By imaging the infrared dielectric response we find that amorphization caused by the nominally 0.5 nm HIB extends throughout the entire 26.5 nm thickness of the cuprate film and by about 500 nm laterally. This unexpectedly widespread structural and electronic damage can be attributed to a Helium depth distribution substantially modified by internal device interfaces. Our study introduces AFM-SNOM as a quantitative nano-scale tomographic technique for non-invasive 3D characterization of irradiation damage in a wide variety of devices.