Effect of Post Deposition Annealing on the Structural and Electrical Properties of NbTiN Thin Films Deposited by Reactive Bias Target Ion Beam Deposition Technique

Nb-based superconducting alloys, such as NbN and NbTiN, can have a superconducting energy gap near twice that of elemental Nb, thus, being ideal candidates for low-loss superconducting circuits operating above the gap frequency of Nb. We are particularly interested in these materials for THz-frequency superconducting-insulating-superconducting (SIS) mixers, kinetic inductance detectors, and traveling wave kinetic inductance parametric amplifier devices. We recently reported the use of an alternative synthesis technique, reactive bias target ion beam deposition (RBTIBD), used to realize high-quality NbTiN films and high-energy gap NbTiN/AlN/NbTiN SIS heterostructures. In this paper, the effect of post-deposition annealing on the electrical and structural properties of room temperature deposited RBTIBD NbTiN was investigated. Our room temperature RBTIBD NbTiN films were annealed using rapid thermal annealing from 200 to 1000 °C. The change in structural and electrical properties was characterized by X-ray diffraction, atomic force microscopy, and four-point probe measurements. The annealed films demonstrated an enhancement in transition temperature (T
_c
), increased crystallinity, larger grain size, and significantly reduced intrinsic stress.