Atomic Layer Deposition of Sodium Fluoride Thin Films

The need for advanced energy conversion and storage devices remains a critical challenge amid the growing worldwide demand for renewable energy. Metal fluoride thin films are of great interest for applications in lithium-ion and emerging rechargeable battery technologies, particularly for enhancing the stability of the electrode-electrolyte interface and thereby extending battery cyclability and lifetime. Reported within, sodium fluoride (NaF) thin films were synthesized via atomic layer deposition. NaF growth experiments were carried out at reactor temperatures between 175 and 250 °C using sodium tert-butoxide and HF-pyridine solution. The optimal deposition temperature range was 175-200 °C, and the resulting NaF films exhibited low roughness (Rq ≈ 1.6 nm for films of ∼8.5 nm), nearly stoichiometric composition (Na:F = 1:1.05) and a growth per cycle value of 0.85 Å/cycle on SiO2 substrates. These results are encouraging for future applications of NaF thin films in the development of improved energy capture and storage technologies.