Correlating the nanostructure of Al-oxide with deposition conditions and dielectric contributions of two-level systems in perspective of superconducting quantum circuits

Abstract

This work is concerned with Al/Al-oxide(AlO${}_x$)/Al-layer systems which are important for Josephson-junction-based superconducting devices such as quantum bits. The device performance is limited by noise, which has been to a large degree assigned to the presence and properties of two-level tunneling systems in the amorphous AlO${}_x$ tunnel barrier. The study is focused on the correlation of the fabrication conditions, nanostructural and nanochemical properties and the occurrence of two-level tunneling systems with particular emphasis on the AlO${}_x$-layer. Electron-beam evaporation with two different processes and sputter deposition were used for structure fabrication, and the effect of illumination by ultraviolet light during Al-oxide formation is elucidated. Characterization was performed by analytical transmission electron microscopy and low-temperature dielectric measurements. We show that the fabrication conditions have a strong impact on the nanostructural and nanochemical properties of the layer systems and the properties of two-level tunneling systems. Based on the understanding of the observed structural characteristics, routes are derived towards the fabrication of Al/AlO${}_x$/Al-layers systems with improved properties.

28 pages, 4 figures

References in corpus (4)

• Observation of directly interacting coherent two-level systems in a solid
• Magnetism in SQUIDs at Millikelvin Temperatures
• Delocalised oxygen as the origin of two-level defects in Josephson junctions
• Atomic delocalisation as a microscopic origin of two-level defects in Josephson junctions

Cited by in corpus (7)

• Optimization of $Al/Al{O}_x/Al$-Layer Systems for Josephson Junctions from a Microstructure Point of View
• Simulating the fabrication of aluminium oxide tunnel junctions
• Alternating Bias Assisted Annealing of Amorphous Oxide Tunnel Junctions
• Structural and Nanochemical Properties of AlOx Layers in $Al/Al{O}_x/Al$-Layer Systems for Josephson Junctions
• Manufacturing high-Q superconducting α-tantalum resonators on silicon wafers
• Mitigating Losses of Superconducting Qubits Strongly Coupled to Defect Modes
• Characterization of process-related interfacial dielectric loss in aluminum-on-silicon by resonator microwave measurements, materials analysis, and imaging