Preparation of Na-Al-O films by laser chemical vapor deposition

Na-Al-O films were prepared on AlN substrates by laser chemical vapor deposition at deposition temperatures (Tdep) of 940-1250 K, molar ratios of Na to Al precursors (RNa/Al) of 0.2-3 and total pressures (Ptot) of 100-800 Pa. Single-phase NaAlO2 films were deposited at Tdep = 940-1080 K, RNa/Al = 1.5-3 and Ptot = 100-800 Pa. The (110)-oriented γ-NaAlO2 films showed roof-like grains, whereas the (200)-oriented γ-NaAlO2 films had finely faceted grains. Single-phase NaAl6O9.5 formed at Tdep = 1018-1125 K, RNa/Al = 0.4-3.0 and Ptot = 100-600 Pa NaAl6O9.5 films had (041) orientation with pyramidally and polygonally faceted grains. At Tdep > 1100 K, α-Al2O3 films, consisting of polygonally faceted grains, formed. The highest deposition rate was 131 μm h−1 for the γ-NaAlO2 film at Tdep = 986 K, RNa/Al = 3.0 and Ptot = 200 Pa.