Influence of strong disorder on superconductivity of MgB2 thin films

Abstract

We investigated the influence of disorder on superconductivity of MgB2 films, prepared in a single deposition run onto two different substrates: (100)-MgO and on (128° rot)-LiNbO3 with trigonal crystal structure which does not match to the MgB2 structure. As expected, the microstructure of both films crucially differs. The REM study shows a very homogeneous, smooth morphology of the MgB2 film on MgO, but a very rough inhomogeneous film structure on LiNbO3. Although the MgB2 film on LiNbO3 is strongly disordered, its critical temperature Tc=33.5 K is practically the same as for the film deposited on MgO. Possible reasons of such unusual Tc behavior are discussed.