Study of Oxygen Incorporation in PLD ${\rm MgB}_{2}$ Films by Rutherford Backscattering Spectroscopy

The Rutherford backscattering (RBS) method has been employed to study the incorporation of oxygen into MgB
₂
films during their fabrication by pulsed-laser deposition (PLD). A series of MgB
₂
thin film samples were analyzed, including two films produced in situ on Al
₂
O
₃
- c substrates (with higher T
_c
and lower T
_c
) with an on-axis geometry, one film produced in situ with an off-axis geometry, and one film produced ex situ, with a bulk-like T
_c
. The amount of oxygen detected by RBS, which is stable in the form of MgO, appears to be correlated with the T
_c
of the films, the higher the T
_c
the lower the oxygen content. The superconducting properties of the thin films are discussed in the context of the RBS results.