Inhomogeneity of the gap from TiN films studied by low-temperature STM*

Titanium nitride films with high kinetic inductance show great promise for use in superconducting qubits and resonators. The magnitude of the kinetic inductance and the loss in the films depend crucially on the preparation conditions and resulting film morphology. Here we report STM measurements performed at 400 mK on a 20 nm-thick high kinetic inductance film and a 40 nm thick oxygen treated film. We have found that in a 40 nm thick film the superconducting gap can be observed after gentle sputter cleaning of the surface. However, we find that the gap can vary from grain to grain by more than 20% and there is significant broadening of the gap in all regions. We will present spatially resolved gap maps on both films, examine the correlation between the surface topography and gap, and discuss some of the implications of these results for superconducting qubits.