Characteristics of Interface-Modified Josephson Junctions  Fabricated under Various Etching Conditions

We propose an output interface with a latching driver for single-flux-quantum (SFQ) circuits operating at 4.2 K. An optimum critical current density of the latching driver was discussed, and a multichip module (MCM) structure with SFQ circuits and latching drivers was proposed for 40-Gb/s operation. To optimize of the latching driver, we calculated the punchthrough probability of Nb-Al-AlO -Nb junctions and high-temperature superconductor (HTS) junctions. The Nb junction with a of 45 kA/cm 2 , which has a hysteresis of 44% for the latching operation, leads to a punchthrough probability lower than 10 15 for an ideal ac-bias of 40 GHz. On the other hand, ramp-edge-type interface-modified junctions based on YBa 2 Cu 3 O 7 have an optimum of 60 kA/cm 2 that gives the smallest punchthrough probability lower than 10 15 for an ideal ac-bias of 40 GHz without any shunt capacitance. Because the optimum of 45 kA/cm 2 for the latching driver is too large to fabricate large-scale integrated SFQ circuits with the Nb junction, the MCM structure consisting of SFQ circuits and latching drivers with the optimum is important to prepare 40-Gb/s SFQ systems. The of 60 kA/cm 2 is a practical value for the HTS junctions, and use of the low-temperature superconductor (LTS)-HTS MCM structure is also one way to realize the high-speed SFQ systems.Index Terms-Interface circuit, latching driver, multichip module (MCM), punchthrough, single-flux quantum (SFQ).

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“…The spreads in of 8% was achieved for a 100-junction series-array on a ground plane at 4.2 K [18]. Fig.…”

Section: Junction Characteristicsmentioning

confidence: 86%

“…Since the initial proposal of the interface-modified ramp-edge junction by Moeckly and Char [15], it has been improved in many laboratories [16]- [18]. The spreads in of 8% was achieved for a 100-junction series-array on a ground plane at 4.2 K [18].…”

Section: Junction Characteristicsmentioning

confidence: 99%

Output Interface With Latching Driver for LTS-SFQ Circuits

Hato

Horibe

Wakana

et al. 2005

IEEE Trans. Appl. Supercond.

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“…Interfaceengineered Josephson junctions (IEJs) have been developed by several institutes [1][2][3][4]. We have already studied the relationship between junction characteristics and process parameters such as etching conditions, and confirmed that junction characteristics are controlled by accelerating the voltage and the etching time during the etching sequence [5,6]. The IEJs have uniformly thin barriers [7,8].…”

Section: Introductionmentioning

confidence: 85%

The improvement of the characteristics of ramp-edge junctions with interface modified barriers

Ito

Horibe

Inagaki

et al. 2001

Supercond. Sci. Technol.

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We have studied the effect of process parameters on uniformity and reproducibility in the engineered barrier ramp-edge Josephson junctions with YBa2Cu3Ox electrodes. The engineered barrier is formed during an etching and annealing process. We investigate excess currents in the junctions by analysing the magnetic field modulations of critical current. The observed excess currents in this study decrease exponentially with increasing annealing temperature. We thus speculate that these excess currents flow via superconductive pinholes in the barrier of the interface-engineered junction (IEJ) due to the formation of CuO2 plane which is formed during the barrier formation. We try to patch these pinholes by substituting Cu and Y for Ga and Pr, respectively. We have found that deposition of amorphous PrGaO3 (PGO) in the IEJ barrier dramatically decreases the excess current.

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“…The main idea is that the YBCO surface can be modified into a non-superconducting material after being exposed to appropriate ion damage. Since this study, there has been a great deal of research on interfacemodified ramp-edge-type HTSC JJ using various methods for interface modification, such as plasma treatment [1][2][3], ion beam damage [4][5][6][7], chemical treatment [7] and base electrode doping [9]. Wen et al argued that the barrier layer, composed of Ba-based cubic perovskite phase, is certainly a derivative compound of YBCO [10].…”

Section: Introductionmentioning

confidence: 99%

Interface-modified YBCO ramp-edge Josephson junctions by deionized water

Kye¹,

Choi²,

Ahn³

et al. 2001

Supercond. Sci. Technol.

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We have investigated YBa 2 Cu 3 O 7−x (YBCO) ramp-edge Josephson junctions by reacting the ramp-edge interface with deionized water. YBa 2 Cu 3 O 7−x /PrBa 2 Cu 3 O x (YBCO/PBCO) films were deposited on SrTiO 3 (1 0 0) by on-axis KrF laser deposition. After patterning the bottom YBCO/PBCO layer, the ramp edge was cleaned by Br-in-ethanol and then reacted with deionized water. The top YBCO/PBCO layer was deposited and patterned by photolithography and ion milling. We measured the current-voltage (I-V ) characteristics, magnetic field modulation of the critical current and microwave response at 10 GHz. The 20-minute water-immersed junction showed resistively shunted junction (RSJ)-type I-V characteristics, while others exhibited flux-flow behaviour. The average values of I c , R n and I c R n of these RSJ-type junctions were 4 mA, 0.1 and 400 µV, respectively, and Shapiro steps were fitted well by the microwave characteristic parameter (= hf/2eI c R n ) = 0.18.

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Characteristics of Interface-Modified Josephson Junctions Fabricated under Various Etching Conditions

Cited by 19 publications

References 11 publications

Output Interface With Latching Driver for LTS-SFQ Circuits

Output Interface With Latching Driver for LTS-SFQ Circuits

The improvement of the characteristics of ramp-edge junctions with interface modified barriers

Interface-modified YBCO ramp-edge Josephson junctions by deionized water

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