Growth and Characterization of Aluminum Thin Films for Superconducting Quantum Devices

The performance of superconducting quantum devices is highly dependent to materials growth and processing [Oh, Jin-Su, et al, Deshpande, Aniruddha, et al, Chayanun L., et al. and Biznárová, Janka, et al.]. We investigate how thin film deposition parameters affect the internal quality factor (Q_i) of coplanar waveguide (CPW) resonators. Aluminum films were deposited at rates from 0.1 to 1.0 nm/s and substrate temperatures ranging from room temperature to 250 °C. In addition, we explored post-deposition treatments to study surface-related loss mechanisms. We conducted microstructural analysis, including grain growth behavior and interface quality, using transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) to investigate the films’ structure and transport measurements to determine the superconducting transition temperature (T_c) and residual resistivity ratio (RRR). Our results demonstrate that deposition conditions significantly influence film quality and resonators internal quality factor, highlighting the importance of materials optimization in superconducting quantum circuits.

References:

Oh, Jin-Su, et al. "Correlating aluminum layer deposition rates, Josephson junction microstructure, and superconducting qubits’ performance." Acta Mater. 284 (2025): 120631.

Deshpande, Aniruddha, et al. "Influence of growth parameters on the superconducting transition temperature in granular aluminum films." arXiv preprint arXiv:2501.03962 (2025).

Chayanun L., et al. "Characterization of process-related interfacial dielectric loss in aluminum-on-silicon by resonator microwave measurements, materials analysis, and imaging." APL Quantum 1.2 (2024).

Biznárová, Janka, et al. "Mitigation of interfacial dielectric loss in aluminum-on-silicon superconducting qubits." Npj Quantum Inf. 10.1 (2024): 78