Enhanced Tantalum Superconducting Resonator Performance via All-Surface Organic Monolayer Passivation

TL;DR

This study demonstrates that organic monolayer surface passivation on tantalum significantly enhances superconducting resonator quality factors by reducing dielectric losses from interfacial two-level systems, advancing quantum device coherence.

Contribution

The paper introduces a molecular surface passivation technique using self-assembled organic monolayers to improve tantalum superconducting resonator performance.

Findings

Achieved internal quality factors up to 1.8x10^6 at 100 mK.

Surface characterization confirms formation of ordered, nanometer-thick films.

Passivation reduces TLS-induced losses, improving device coherence by ~140%.

Abstract

Tantalum is a promising platform for superconducting quantum circuits, yet coherence times remain limited by dielectric losses from interfacial two-level systems (TLS), exacerbated by native oxide regrowth. Here, we implement molecular surface passivation using self-assembled organic monolayers on freshly etched tantalum and silicon in coplanar waveguide resonators. Surface characterization by contact angle, XPS, FTIR and TEM confirm the formation of ordered, nanometer-thick films that suppress oxide formation. Microwave measurements in the ~5-9 GHz range reveal internal quality factors up to 1.8x10^6 in the single-photon regime at 100 mK, representing a ~140% improvement over untreated devices with native oxide. Power and temperature dependent measurements attribute this enhancement to reduced TLS-induced losses. These results demonstrate that molecular passivation effectively engineers low-loss interfaces and provides a scalable route toward high-coherence superconducting quantum devices.