Two-stage Atomic Layer Deposition of Smooth Aluminum Oxide on Hydrophobic Self-assembled Monolayers

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). 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. In order 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.