# Plasma-Enhanced Atomic Layer Deposition of AlF3 Antireflective Coatings via Pulse-Time Control of Fluorine Radical Reactions

## TL;DR

Scientists developed a new method to create high-quality, non-corrosive AlF3 coatings that improve glass transparency by controlling plasma reactions.

## Contribution

A safe, HF-free PEALD process for AlF3 coatings is introduced, linking plasma kinetics to optical performance.

## Key findings

- Optimized plasma pulse durations enable ultra-low impurity AlF3 films with atomically smooth surfaces.
- The process achieves 97.6% optical transmittance in glass, demonstrating high performance.
- A hydrogen-terminated fluorinated surface (s-FH) was identified as key to the reaction pathway.

## Abstract

Plasma-enhanced atomic layer deposition (PEALD) is used to grow high-quality aluminum fluoride (AlF3) antireflective coatings via a safe, HF-free route using trimethylaluminum and SF6 plasma. In situ diagnostics reveal a reaction pathway mediated by a hydrogen-terminated fluorinated surface (s-FH). By systematically varying the plasma pulse duration, a critical process window is identified that balances efficient ligand removal against ion-induced structural damage. Within this optimized window, the films achieve ultra-low impurity levels and an atomically smooth morphology, increasing the optical transmittance of glass to (97.6 ± 0.5)%. This study establishes a clear link between fundamental plasma kinetics and functional optical performance, providing a robust, non-corrosive strategy for the rational design of metal–fluoride PEALD coatings.