Fabrication of Superconducting Qubits with Al Trilayer Josephson Junctions

Satoh, T.; Noguchi, Yoshiji; Yamagishi, M; Nagasawa, Shuichi; Hinode, K.; Hidaka, Mutsuo; Maezawa, M.; Horikawa, T.

doi:10.1109/tasc.2014.2378033

Cited by 8 publications

(7 citation statements)

References 24 publications

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“…By comparison, the size of junctions in real circuits usually exceeds 100 nm. 7,18 For this reason periodic boundary conditions are applied during the development of the junction model.…”

Section: Atomistic Junction Modelmentioning

confidence: 99%

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Effect of atomic structure on the electrical response of aluminum oxide tunnel junctions

Cyster

Smith

Vaitkus

et al. 2020

Phys. Rev. Research

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Many nanoelectronic devices rely on thin dielectric barriers through which electrons tunnel. For instance, aluminium oxide barriers are used as Josephson junctions in superconducting electronics. The reproducibility and drift of circuit parameters in these junctions are affected by the uniformity, morphology, and composition of the oxide barriers. To improve these circuits the effect of the atomic structure on the electrical response of aluminium oxide barriers must be understood. We create three-dimensional atomistic models of aluminium oxide tunnel junctions and simulate their electronic transport properties with the non-equilibrium Green's function formalism. Increasing the oxide density is found to produce an exponential increase in the junction resistance. In highly oxygen-deficient junctions we observe metallic channels which decrease the resistance significantly.Computing the charge and current density within the junction shows how variation in the local potential landscape can create channels which dominate conduction. An atomistic approach provides a better understanding of these transport processes and guides the design of junctions for nanoelectronics applications.

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“…By comparison, the size of junctions in real circuits usually exceeds 100 nm. 7,18 For this reason periodic boundary conditions are applied during the development of the junction model.…”

Section: Atomistic Junction Modelmentioning

confidence: 99%

“…[1][2][3][4][5] These qubits rely on the non-linear response of Josephson junctions which are often fabricated as Al-AlO x -Al tri-layer junctions. [6][7][8] As we move to large-scale quantum computer engineering, it becomes critical to understand what limits junction performance and variability.…”

Section: Introductionmentioning

confidence: 99%

Effect of atomic structure on the electrical response of aluminum oxide tunnel junctions

Cyster

Smith

Vaitkus

et al. 2020

Phys. Rev. Research

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“…The aluminium layers are deposited through a lithographic mask at different angles to a substrate with an intervening low pressure oxidation which forms the oxide barrier 10 . Other fabrication methods which modify or even remove the standard Dolan bridge structure also employ a low-pressure oxidation step [11][12][13] .…”

Section: Introductionmentioning

confidence: 99%

Simulating the fabrication of aluminium oxide tunnel junctions

et al. 2021

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Aluminium oxide (AlOx) tunnel junctions are important components in a range of nanoelectric devices including superconducting qubits where they can be used as Josephson junctions. While many improvements in the reproducibility and reliability of qubits have been made possible through new circuit designs, there are still knowledge gaps in the relevant materials science. A better understanding of how fabrication conditions affect the density, uniformity, and elemental composition of the oxide barrier may lead to the development of lower noise and more reliable nanoelectronics and quantum computers. In this paper, we use molecular dynamics to develop models of Al–AlOx–Al junctions by iteratively growing the structures with sequential calculations. With this approach, we can see how the surface oxide grows and changes during the oxidation simulation. Dynamic processes such as the evolution of a charge gradient across the oxide, the formation of holes in the oxide layer, and changes between amorphous and semi-crystalline phases are observed. Our results are widely in agreement with previous work including reported oxide densities, self-limiting of the oxidation, and increased crystallinity as the simulation temperature is raised. The encapsulation of the oxide with metal evaporation is also studied atom by atom. Low density regions at the metal–oxide interfaces are a common feature in the final junction structures which persists for different oxidation parameters, empirical potentials, and crystal orientations of the aluminium substrate.

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“…10 Other fabrication methods which modify or even remove the standard Dolan bridge structure also employ a low pressure oxidation step. [11][12][13] In this study we use molecular dynamics (MD) to explicitly model the low pressure oxidation and aluminium evaporation processes. The structure of the oxide and junction emerge as oxygen and aluminium atoms are consecutively added to the surface.…”

Section: Introductionmentioning

confidence: 99%

Simulating the fabrication of aluminium oxide tunnel junctions

Cyster,

Smith,

Vogt

et al. 2020

Preprint

View full text Add to dashboard Cite

Aluminium oxide (AlOx) tunnel junctions are important components in a range of nanoelectric devices including superconducting qubits where they can be used as Josephson junctions. While many improvements in the reproducibility and reliability of qubits have been made possible through new circuit designs, there are still knowledge gaps in the relevant materials science. A better understanding of how fabrication conditions affect the density, uniformity, and elemental composition of the oxide barrier may lead to the development of lower noise and more reliable nanoelectronics and quantum computers. In this paper we use molecular dynamics to develop models of Al-AlOx-Al junctions by iteratively growing the structures with sequential calculations. With this approach we can see how the surface oxide grows and changes during the oxidation simulation. Dynamic processes such as the evolution of a charge gradient across the oxide, the formation of holes in the oxide layer, and changes between amorphous and semi-crystalline phases are observed. Our results are widely in agreement with previous work including reported oxide densities, self-limiting of the oxidation, and increased crystallinity as the simulation temperature is raised. The encapsulation of the oxide with metal evaporation is also studied atom by atom. Low density regions at the metaloxide interfaces are a common feature in the final junction structures which persists for different oxidation parameters, empirical potentials, and crystal orientations of the aluminium substrate.

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Fabrication of Superconducting Qubits with Al Trilayer Josephson Junctions

Cited by 8 publications

References 24 publications

Effect of atomic structure on the electrical response of aluminum oxide tunnel junctions

Effect of atomic structure on the electrical response of aluminum oxide tunnel junctions

Simulating the fabrication of aluminium oxide tunnel junctions

Simulating the fabrication of aluminium oxide tunnel junctions

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