  Electronic applications of carbon nanotubes (CNTs) require the deposition of
dielectric films on the tubes while conserving their excellent electronic
properties. In our density functional theory study we use the trimethylaluminum
(TMA) atomic layer deposition (ALD) as a model process for a
CNT-functionalization. Since this functionalization relies on the presence of
OH-groups, the CNTs are exposed to a water or oxygen pre-treatment. We show
that only CNTs with a single-vacancy defect are able to react with H$_{2}$O or
O$_{2}$. Further, the defect is preferably saturated by oxygen. This leaves the
CNT without the necessary hydroxyl groups for the first TMA addition.
Therefore, we propose an alternative initial step after which a classical TMA
ALD process can be performed on the CNT.
