  Depositing disordered Al on top of SrTiO$_3$ is a cheap and easy way to
create a two-dimensional electron system in the SrTiO$_3$ surface layers. To
facilitate future device applications we passivate the heterostructure by a
disordered LaAlO$_3$ capping layer to study the electronic properties by
complementary x-ray photoemission spectroscopy and transport measurements on
the very same samples. We also tune the electronic interface properties by
adjusting the oxygen pressure during film growth.
