Elevating performance of AlOxFy anti-reflection coating via controllable HF vapor fluorination

•Successful chemical modification of Al2O3 to AlOxFy using an atomic layer deposition system is demonstrated.•Systematic fluorination conditions are managed in three steps of HF vapor supply.•The abundant pores in Al2O3 film derived by a solution process plays an important role in fluorination by facilitating the reliable delivery of HF molecules.•Anti-reflection performance is boosted by lower the refractive index.•Chemical transformation provides chemical and optical durability, which is crucial for practical uses of anti-reflection coating.