  We present X-ray photoelectron spectroscopy data which show that the
chemisorbed oxygen previously observed to be on the surface of thin AlOx layers
formed by room temperature thermal oxidation is bound by oxygen vacancies in
the oxide. Increasing the electric field across the oxide, either by
over-coating with a metallic electrode, or by electron bombardment, drives this
surface chemisorbed oxygen into the vacancy sites. Due to the low bonding
energies of these oxygen sites, subsequent oxygen exposures draw these ions
back to the surface, reforming chemisorbed O$_2^-$. Al/AlOx/Al tunnel junctions
incorporating electron bombarded AlOx barriers show a significant reduction in
the low frequency junction resistance noise level at 4.2 K.
