Corrosion Resistance of Atomic Layer Deposition-Generated Amorphous Thin Films.

Atomic layer deposition (ALD) was used to prepare amorphous thin films of AlO, NbO, and TaO on both silicon substrates and aluminum blocks. Etch rates in 10 M NHOH were determined from X-ray reflectometry data collected as a function of time. Amorphous AlO thin films were found to have an etch rate of 0.5 nm min and an increase in roughness of ∼0.01 nm min. Electron microscopy data showed etch pits, consistent with the increase in roughness. Amorphous NbO and TaO films showed no appreciable etching or roughening over the course of a ∼500 h continuous immersion. An NbO-coated aluminum block showed no corrosion after immersion in 10 M NHOH for over 200 h, suggesting that the coatings were pinhole-free. These results suggest that amorphous ALD thin films of NbO and TaO are candidates as barrier layers for aluminum in caustic environments.