Thermal annealing of superconducting niobium titanium nitride thin films deposited by plasma-enhanced atomic layer deposition

Abstract

Next-generation superconducting radio frequency (SRF) cavities, based on tailored thin films, would allow for more efficient and sustainable accelerators operating at higher accelerating gradients. In particular, superconductor–insulator–superconductor (SIS) multilayers are proposed as a potential alternative to bulk Nb. In this context, NbTiN stands out as a superconducting candidate. Here, we report our studies on NbTiN thin films grown by plasma-enhanced atomic layer deposition (PEALD) in a supercycle approach on AlN in situ deposited on planar silicon substrates. In detail, different ternary compound compositions and thicknesses have been investigated concerning the elemental composition, the superconducting properties, and the crystallinity of the deposited thin films. Two different post-deposition thermal treatments have been applied to Nb0.75Ti0.25N thin films of different thicknesses. Their effect on the film properties has been evaluated. It has been demonstrated that an optimized post-deposition thermal annealing procedure significantly improves the quality of our PEALD deposited Nb0.75Ti0.25N thin films, achieving the highest superconducting critical temperature (Tc) of 15.9 K obtained for films deposited by atomic layer deposition (ALD) so far and a lower critical field (Hc1) of 213 mT, which overpasses the bulk Nb intrinsic limit of 200 mT. Our studies are a promising first stepping stone on the path toward tailored thin films based SRF cavities.

Field Emission from Carbon Nanotubes on Titanium Nitride-Coated Planar and 3D-Printed Substrates

“…The 10 nm thick TiN films were deposited in a PEALD system (GEMStar XT-DP TM , Arradiance, Littleton, MA, USA) in continuous flow mode at a temperature of 250 • C using tetrakis(dimethylamino)titanium(IV) (TDMAT, Strem Chemicals, Newburyport, MA, USA) as the titanium source in combination with a hydrogen/nitrogen plasma. The detailed description of the TiN cycle can be found in a previous publication [34].…”

Reducing the Thermal Effects during Coating of Superconducting Radio-Frequency Cavities: A Case Study for Atomic Layer Deposition of Alumina with a Combined Numerical and Experimental Approach

“…These treatments have enabled Nb cavities to achieve quality factors ( Q 0 ) higher than those of previous records, all while maintaining their performance with increasing gradients. These advancements encompass methods such as nitrogen doping and infusion as well as mid-T baking. − To move beyond the intrinsic limitations of niobium, only few concepts have been suggested including superconductor–insulator-superconductor (SIS) multilayer structures. − Coating the inner surface of Nb cavities with thin films or multilayers of superconductors, such as NbN or NbTiN, and insulators, such as Al 2 O 3 or AlN, holds the potential to create advanced composite accelerator cavities. These coated cavities are anticipated to outperform traditional Nb cavities, achieving lower RF losses and higher accelerating gradients, potentially exceeding 100 MV/m .…”