Superconductive devices for millimeter wave detection, mixing, and amplification

Richards, P. L.; Shen, T. M.

doi:10.1109/t-ed.1980.20128

Cited by 57 publications

(7 citation statements)

References 41 publications

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“…Superconducting devices are frequently based on Josephson junctions (JJ) fabricated on the basis of Al/AlOx/Al-layer systems where a thin AlOx layer serves as tunnel barrier. JJs are used, e.g., in superconducting quantum bits for the realization of quantum information circuits [1], single photon detectors [2], radiation detectors [3], single electron transistors [4] and superconducting quantum interference devices in magnetometers [5,6]. The structural properties of the layer system have a profound influence on the performance of superconducting devices and on noise that limits detection sensitivity and coherence.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Al/AlOx/Al-layer systems for Josephson junctions from a microstructure point of view

Fritz

Radtke

Schneider

et al. 2019

Journal of Applied Physics

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Al/AlOx/Al-layer systems are frequently used for Josephson junction-based superconducting devices. Although much work has been devoted to the optimization of the superconducting properties of these devices, systematic studies on influence of deposition conditions combined with structural analyses on the nanoscale are rare up to now. We have focused on the optimization of the structural properties of Al/AlOx/Al-layer systems deposited on Si (111) substrates with a particular focus on the thickness homogeneity of the AlOx-tunnel barrier. A standard high-vacuum electron-beam deposition system was used and the effect of substrate pretreatment, different Al-deposition temperatures and Al-deposition rates was studied. Transmission electron microscopy was applied to analyze the structural properties of the Al/AlOx/Al-layer systems to determine the thickness homogeneity of the AlOx layer, grain size distribution in the Al layers, Al-grain boundary types and the morphology of the Al/AlOx interface. We show that the structural properties of the lower Al layer are decisive for the structural quality of the whole Al/AlOx/Al-layer system. Optimum conditions yield an epitaxial Al(111) layer on a Si(111) substrate with an Al-layer thickness variation of only 1.6 nm over more than 10 m and large lateral grain sizes up to 1 m. Thickness fluctuations of the AlOx-tunnel barrier are minimized on such an Al layer which is essential for the homogeneity of the tunnel current. Systematic variation of the Al-deposition rate and deposition temperature allows to develop an understanding of the growth mechanisms.

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Section: Introductionmentioning

confidence: 99%

Optimization of Al/AlOx/Al-layer systems for Josephson junctions from a microstructure point of view

Fritz

Radtke

Schneider

et al. 2019

Journal of Applied Physics

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“…Aluminum oxide (AlOx) layers are important components of several state-of-the-art electronic devices and decisive for their electronic properties. Thin AlOx-tunnel barriers with a thickness of ~2 nm are widely used in Al/AlOx/Al-based Josephson junctions (JJs) for superconducting electronic devices like superconducting quantum bits, single-electron transistors, single-photon detectors, radiation detectors and superconducting quantum interference devices in magnetometers [1][2][3][4][5][6][7]. Amorphous AlOx layers with a thickness of a few nanometers are used as gate dielectrics in high-gain graphene field-effect transistors [8,9], as gate oxide in III-V compound semiconductor-based field-effect transistors [10,11] or as layers in non-volatile resitive switching random access memories [12,13].…”

Section: Introductionmentioning

confidence: 99%

Structural and nanochemical properties ofAlOxlayers inAl/AlOx/Al-layer systems

Fritz

Radtke

Schneider

et al. 2019

Phys. Rev. Materials

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The structural and nanochemical properties of thin AlOx 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 AlOx 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 AlOx layers and correlate them with fabrication parameters. With respect to the application of AlOx as tunnel barrier in superconducting Josephson junctions, Al/AlOx/Al-layer systems were deposited on Si substrates. We will show that the oxygen content and structure of amorphous AlOx layers is strongly dependent on the fabrication process and oxidation parameters.Dynamic and static oxidation of Al yields oxygen-deficient amorphous AlOx 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 -Al2O3 layers were grown by electron-beam evaporation of Al2O3 and reactive sputter deposition.

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“…Minimum [12]. Below 100 GHz excellent noise equivalent powers have been achieved with photon assisted quasi-particle tunneling in SIS-devices (superconductorinsulator-superconductor) [18]. For this purpose hysteretic tunnel oxide Josephson junctions are biased near the gap voltage 2A/e just below the 22 U, /MVsharp rise of the quasi-particle current, after the zero voltage current has been suppressed by a magnetic field as sketched in Fig.…”

Section: Single Josephson Junctionmentioning

confidence: 99%