Structural and Nanochemical Properties of AlOx Layers in $Al/Al{O}_x/Al$-Layer Systems for Josephson Junctions

Abstract

The structural and nanochemical properties of thin $Al{O}_x$ layers are decisive for the performance of advanced electronic devices. For example, they are frequently used as tunnel barriers in Josephson junction-based superconducting devices. However, systematic studies of the influence of oxidation parameters on structural and nanochemical properties are rare up to now, as most studies focus on the electrical properties of $Al{O}_x$ layers. This study aims to close this gap by applying transmission electron microscopy in combination with electron energy loss spectroscopy to analyze the structural and nanochemical properties of differently fabricated $Al{O}_x$ layers and correlate them with fabrication parameters. With respect to the application of $Al{O}_x$ as tunnel barrier in superconducting Josephson junctions, $Al/Al{O}_x/Al$-layer systems were deposited on Si substrates. We will show that the oxygen content and structure of amorphous $Al{O}_x$ layers is strongly dependent on the fabrication process and oxidation parameters. Dynamic and static oxidation of Al yields oxygen-deficient amorphous $Al{O}_x$ layers, where the oxygen content ranges from x = 0.5 to x = 1.3 depending on oxygen pressure and substrate temperature. Thicker layers of stoichiometric crystalline $\gamma -A{l}_2{O}_3$ layers were grown by electron-beam evaporation of $A{l}_2{O}_3$ and reactive sputter deposition.

References in corpus (4)

• Magnetism in SQUIDs at Millikelvin Temperatures
• Delocalised oxygen as the origin of two-level defects in Josephson junctions
• Current noise of a superconducting single electron transistor coupled to a resonator
• Atomic delocalisation as a microscopic origin of two-level defects in Josephson junctions

Cited by in corpus (5)

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• Alternating Bias Assisted Annealing of Amorphous Oxide Tunnel Junctions
• Probing hundreds of individual quantum defects in polycrystalline and amorphous alumina
• Material matters in superconducting qubits
• Analysis of Josephson Junction Barrier Variation: A Combined Electron Microscopy, Breakdown and Monte-Carlo Approach