Two‐stage Atomic Layer Deposition: Deposition of Aluminum Oxide Films on Hydrophilic and Hydrophobic Surfaces

We describe the growth of aluminum oxide $(AlOx)$ on strong hydrophobic surfaces that consist of $CH3$‐terminated self‐assembled monolayers (⁠$CH3$‐SAMs) by utilizing atomic layer deposition (ALD) with $H2O$ as the oxygen source. The evolution of $AlOx$ on the $CH3$‐SAMs was studied by comparing with that on hydrophilic OH‐terminated silicon dioxide (OH‐$SiO2$⁠) surfaces. The $AlOx$ grown on the $CH3$‐SAM surfaces underwent growth instability and developed significantly rough surface morphologies while the $AlOx$ on the OH‐$SiO2$ maintained atomically smooth surface morphologies. The structural integrity of the $CH3$‐SAMs was also found to be disturbed substantially at the onset of the ALD process with $H2O.$ To improve the surface morphology of $AlOx$ on $CH3$‐SAM surfaces, a two‐stage ALD process was developed. In the two‐stage ALD process for $AlOx,$ the first stage utilized n‐propanol as the oxygen source and the second stage proceeded with $H2O.$ The optimized two‐stage ALD process significantly improved the surface morphology of $AlOx$ films and effectively protected the structural integrity of underlying $CH3$‐SAMs.