  We have investigated the dimensionality and origin of the magnetotransport
properties of LaAlO3 films epitaxially grown on TiO2-terminated SrTiO3(001)
substrates. High mobility conduction is observed at low deposition oxygen
pressures (PO2 < 10^-5 mbar) and has a three-dimensional character. However, at
higher PO2 the conduction is dramatically suppressed and nonmetallic behavior
appears. Experimental data strongly support an interpretation of these
properties based on the creation of oxygen vacancies in the SrTiO3 substrates
during the growth of the LaAlO3 layer. When grown on SrTiO3 substrates at low
PO2, other oxides generate the same high mobility as LaAlO3 films. This opens
interesting prospects for all-oxide electronics.
