  We have studied the chemical and electronic properties of LaAlO3/SrVO3
ultrathin films by combining hard x-ray photoemission spectroscopy and
transport measurements. We compare single SrVO3 (SVO) ultrathin films and SrVO3
buried below a polar LaAlO3 (LAO) thin layer, both epitaxially grown on SrTiO3.
While ultrathin films (4 unit cells) of SVO do show insulating behavior over
the entire temperature range, the LAO/SVO interface has a resistivity minimum
at 250 K. When increasing the SVO layer thickness, the minimum is observed to
shift to higher temperatures, but the resistivity stays always smaller than
that of comparable SVO single films. Hard x-ray photoemission spectroscopy
reveals a surface or interface related V5+ component in the V 2p spectra for
SVO films and LAO/SVO heterostructures, respectively, attributed to a strongly
oxidized component. This chemical reconstruction is weaker in LAO/SVO
heterostructures compared to single SVO films. We show that this dead layer in
SVO ultrathin films has to be considered when the film thickness reaches the
few unit-cells limit and propose solutions on how to prevent this detrimental
effect.
