Superconducting Nb<i>x</i>Ti1−<i>x</i>N prepared at high deposition rates with plasma-enhanced atomic layer deposition and substrate biasing

Superconducting films ranging from a few to hundreds of nanometers thickness are integral to a wide range of quantum devices. The further development of quantum technologies hinges on material advances. With its atomic-scale growth control, plasma-enhanced atomic layer deposition (PEALD) is very promising as an enabling technique for the growth of superconducting thin films. This work demonstrates high deposition rates of ∼30–60 nm/h in PEALD of superconducting NbxTi1−xN films through a supercycle process with accurate composition control. The film thicknesses vary from 4 to 97 nm. All prepared films are face-centered cubic polycrystalline with low ∼1 at. % O content. Accurate ion-energy control by means of RF substrate biasing yields an improved electrical resistivity for 30 nm Nb0.5Ti0.5N films from 497 ± 45 μΩ cm (grounded substrate) down to 184 ± 19 μΩ cm (−81 V bias) through its impact on structural properties. Substrate biasing results in an increase in film disorder while enhancing mass density. A 6–7 K critical temperature (Tc) of superconductivity is measured for 30 nm Nb0.5Ti0.5N films, which does not show strong variations with substrate bias. The tunability and high deposition rate of the NbxTi1−xN deposition process puts forward PEALD as a promising technique to tackle material challenges in quantum technology.