# Tin–Lead Liquid Metal Alloy Source for Focused Ion Beams

## TL;DR

This paper introduces a tin-lead alloy for focused ion beams, enabling precise ion implantation for quantum applications like single photon emitters in diamond.

## Contribution

The study presents a novel Pb-containing alloy and emitter materials for FIB systems suitable for quantum information science.

## Key findings

- Pb-containing alloys with eutectic points below 600 °C were developed for FIB systems.
- Ta and Ti were identified as effective emitter materials for Pb liquid metal alloy ion sources.
- Standard FIB systems can resolve Pb isotopes and achieve nanoscale spot sizes for quantum applications.

## Abstract

Focused Ion Beam (FIB) systems are increasingly utilized in nanotechnology for nanostructuring, surface modification, doping, and rapid prototyping. Recently, their potential for quantum applications has been explored, leveraging FIB’s direct-write capabilities for in situ single ion implantation, which is crucial for fabricating single photon emitters. Color centers in diamond can function as qubits and are of particular interest due to their capacity to store and transmit quantum information. While Group-IV color centers exhibit high brightness, they require low temperatures to retain coherence. However, lead-vacancy in diamond (PbV) operates at the higher end (4 K) of this temperature spectrum due to larger ground-state splitting, making them particularly interesting. In this context, our study presents results for lead (Pb)-containing alloys with eutectic points below 600 °C and results on using tantalum (Ta) and titanium (Ti) as emitter materials for a Pb liquid metal alloy ion source. We show that a standard FIB system is able to resolve the different Pb isotopes and achieve nanoscale spot sizes, as required for quantum information science applications.