Engineering Structure–Property Correlations in Transition-Metal Nitrides for Next-generation Superconducting Quantum Platforms

Presenter: Dr. Mythili Surendan, Lawrence Berkeley National Laboratory

Abstract:

Superconducting transition metal nitrides such as niobium nitride (NbN), titanium nitride (TiN) and their alloys are key for next-generation quantum technologies due to their promising superconducting properties and compatibility with semiconductor fabrication processes. However, optimizing their performance requires precise control over thin-film growth to tailor crystallinity, stoichiometry, and defect density.

In this work, I present a comprehensive investigation of NbN thin films grown by DC reactive sputtering in a cluster tool system at Foundry’s Nanofabrication facility. Using structural, chemical, and electrical characterization, we establish how microstructure and composition correlate with superconducting performance. We systematically vary key growth parameters—including substrate choice, deposition temperature and nitrogen partial pressure—to elucidate their influence on crystallinity and high critical temperature (Tc) superconducting phase formation in nitride films.

We further map the dependence of Tc, upper critical field, and superconducting gap on film structure and stoichiometry, and correlate these properties to superconducting quantum device performance. Kinetic inductance resonators further reveal the impact of disorder on microwave performance through power- and temperature-dependent quality factor measurements. This work establishes a robust framework for the design, synthesis, and optimization of high-quality superconducting nitride films for scalable quantum circuits and devices.

Bio:

Mythili Surendran is a Postdoctoral Scholar at the Molecular Foundry since 2024, where she is part of the Quantum Cluster Tool initiative. Her research focuses on developing materials synthesis, characterization, and device fabrication capabilities for next-generation quantum devices, including superconducting qubits and microwave kinetic inductance detectors. Mythili received her Ph.D. in Materials Science from the University of Southern California, where she developed novel epitaxial growth strategies for complex oxides and chalcogenides using pulsed laser deposition. Her work bridges fundamental materials science and quantum engineering, with the goal of advancing scalable quantum hardware through atomic-level control of thin film heterostructures.