Sol–gel-derived thin-film stacks with high radiation stability

• High-quality titania–silica thin-film stacks were fabricated by sol–gel chemistry.
• Effect of annealing on sample stability was investigated.
• Annealing increases intra-layer stability but decreases inter-layer stability.
• Flash-heated Bragg stacks (no annealing) display the highest radiation stability.

Crack-free thin-film stacks of silica and titania layers were prepared by a sol–gel dip-coating process involving flash-heating and shock-cooling steps. The final Bragg stacks were thermally annealed at different temperatures and their properties were investigated. While annealing increased the intra-layer properties (layer densification, increased crystallinity), it weakened inter-layer strength, leading to cracking and delamination under high-power laser irradiation. In contrast, stacks that were flash-heated only showed excellent radiation stability.