Field-effect Tuning of the carrier density in Nd1.2Ba1.8Cu3Oy Thin Films

Using a field effect device we modified the number of holes in the surface layers of 4 to 10 unit cell Nd1.2Ba1.8Cu3Oy ~NBCO! epitaxial films grown on ~100! SrTiO3 substrates. The results obtained on a set of 12 devices demonstrate that it is possible to induce reversible changes of the hole density of NBCO films by field effect. It is found that the field effect becomes less pronounced increasing the film thickness. Insulating-superconducting transition was observed in one 8 unit cell NBCO field effect device.