  Structural and superconducting properties of magnesium diboride thin films
grown by pulsed laser deposition on zirconium diboride buffer layers were
studied. We demonstrate that the ZrB2 layer is compatible with the MgB2 two
step deposition process. Synchrotron radiation measurements, in particular
anomalous diffraction measurements, allowed to separate MgB2 peaks from ZrB2
ones and revealed that both layers have a single in plane orientation with a
sharp interface between them. Moreover, the buffer layer avoids oxygen
contamination from the sapphire substrate. The critical temperature of this
film is near 37.6 K and the upper critical field measured at Grenoble High
Magnetic Field Laboratory up to 20.3 T is comparable with the highest ones
reported in literature.
