# XeF$_2$-Enhanced Focused Ion Beam Etching and Passivation of GaSb

## TL;DR

This paper presents a novel XeF$_2$-assisted focused ion beam technique for GaSb that reduces surface contamination and nanofibre growth, enabling precise, cost-effective modification and passivation of GaSb-based optoelectronic devices.

## Contribution

It introduces a gas-assisted FIB method using XeF$_2$ to improve GaSb etching and passivation, overcoming previous limitations in III-V material processing.

## Key findings

- Reduced surface roughness and contamination levels.
- Suppressed nanofibre growth via gallium fluoride formation.
- Enables cost-effective, site-specific GaSb device modification.

## Abstract

Focused ion beams (FIBs) are widely used to modify optoelectronic devices, but their utility is severely restricted in some III-V materials due to adverse effects such as nanofibre growth and contamination. This study describes an effective machining method for the modification and passivation of GaSb using a focused Ga$^+$ beam with the addition of XeF$_2$ gas. The added gas suppressed the nanofibre growth and allowed for controlled etching. Moreover, the milled surface exhibited much lower roughness and contained much lower levels of carbon and oxygen contaminants. These effects are attributed to the formation of a gallium fluoride layer, which inhibits the catalytic vapour-liquid-solid (VLS) nanofibre growth. The fluoride layer prevents the surface oxidation, acting as an effective passivation layer. This gas-assisted FIB process eliminates the idiosyncratic challenges of modifying GaSb with an ion beam and it can be implemented cost-effectively and rapidly in conventional FIB systems---allowing for site-specific modification of bespoke GaSb-based devices.