Development of Thin Film Multilayer Structures with Smooth Surfaces for HTS SFQ Circuits

Hironori WAKANA; Seiji ADACHI; Ai KAMITANI; Kouhei NAKAYAMA; Yoshihiro ISHIMARU; Yoshinobu TARUTANI; Keiichi TANABE

doi:10.1093/ietele/e88-c.2.208

Development of Thin Film Multilayer Structures with Smooth Surfaces for HTS SFQ Circuits

Hironori WAKANA, Seiji ADACHI, Ai KAMITANI, Kouhei NAKAYAMA, Yoshihiro ISHIMARU, Yoshinobu TARUTANI, Keiichi TANABE

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We have fabricated a multilayer structure for single flux quantum (SFQ) circuit application using a high-temperature superconductor (HTS). La_0.2-Y_0.9Ba_1.9Cu₃O_x (La-YBCO) base electrode layers were prepared by a dc or rf magnetron sputtering method. The reproducibility of film quality for dc-sputtered La-YBCO films was better than that for rf-sputtered films, and the dc sputtered films exhibited the average surface roughness R_a less than 1.0 nm and a T_c zero value of 88 K. By using the dc-sputtered La-YBCO films, a multilayer structure of SrSnO₃/La-YBCO/SrSnO₃/La-YBCO on MgO substrate with R_a below 2.0 nm was obtained. Interface-modified ramp-edge junctions with La_0.2-Yb_0.9Ba_1.9Cu₃O_x (La-YbBCO) counter electrodes have been fabricated by using this multilayer structure with dc-sputtered films. The fabricated junctions exhibited RSJ-type I-V characteristics with I_cR_n products of about 3 mV at 4.2 K. We also obtained a 1-σ I_c spread of 8% for a 1000-junction series-array. The sheet inductance values at 4.2 K for the base and counter electrodes on La-YBCO ground planes were 0.8 pH and 0.7 pH per square, respectively. Operation of several types of elementary SFQ circuits has been successfully demonstrated by using this multilayer structure.

Publication: IEICE TRANSACTIONS on Electronics Vol.E88-C No.2 pp.208-215

Publication Date: 2005/02/01

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DOI: 10.1093/ietele/e88-c.2.208

Type of Manuscript: Special Section INVITED PAPER (Special Section on Superconducting Electronic Devices and Their Applications)

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Hironori WAKANA, Seiji ADACHI, Ai KAMITANI, Kouhei NAKAYAMA, Yoshihiro ISHIMARU, Yoshinobu TARUTANI, Keiichi TANABE, "Development of Thin Film Multilayer Structures with Smooth Surfaces for HTS SFQ Circuits" in IEICE TRANSACTIONS on Electronics, vol. E88-C, no. 2, pp. 208-215, February 2005, doi: 10.1093/ietele/e88-c.2.208.
Abstract: We have fabricated a multilayer structure for single flux quantum (SFQ) circuit application using a high-temperature superconductor (HTS). La_0.2-Y_0.9Ba_1.9Cu₃O_x (La-YBCO) base electrode layers were prepared by a dc or rf magnetron sputtering method. The reproducibility of film quality for dc-sputtered La-YBCO films was better than that for rf-sputtered films, and the dc sputtered films exhibited the average surface roughness R_a less than 1.0 nm and a T_c zero value of 88 K. By using the dc-sputtered La-YBCO films, a multilayer structure of SrSnO₃/La-YBCO/SrSnO₃/La-YBCO on MgO substrate with R_a below 2.0 nm was obtained. Interface-modified ramp-edge junctions with La_0.2-Yb_0.9Ba_1.9Cu₃O_x (La-YbBCO) counter electrodes have been fabricated by using this multilayer structure with dc-sputtered films. The fabricated junctions exhibited RSJ-type I-V characteristics with I_cR_n products of about 3 mV at 4.2 K. We also obtained a 1-σ I_c spread of 8% for a 1000-junction series-array. The sheet inductance values at 4.2 K for the base and counter electrodes on La-YBCO ground planes were 0.8 pH and 0.7 pH per square, respectively. Operation of several types of elementary SFQ circuits has been successfully demonstrated by using this multilayer structure.
URL: https://globals.ieice.org/en_transactions/electronics/10.1093/ietele/e88-c.2.208/_p

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@ARTICLE{e88-c_2_208,
author={Hironori WAKANA, Seiji ADACHI, Ai KAMITANI, Kouhei NAKAYAMA, Yoshihiro ISHIMARU, Yoshinobu TARUTANI, Keiichi TANABE, },
journal={IEICE TRANSACTIONS on Electronics},
title={Development of Thin Film Multilayer Structures with Smooth Surfaces for HTS SFQ Circuits},
year={2005},
volume={E88-C},
number={2},
pages={208-215},
abstract={We have fabricated a multilayer structure for single flux quantum (SFQ) circuit application using a high-temperature superconductor (HTS). La_0.2-Y_0.9Ba_1.9Cu₃O_x (La-YBCO) base electrode layers were prepared by a dc or rf magnetron sputtering method. The reproducibility of film quality for dc-sputtered La-YBCO films was better than that for rf-sputtered films, and the dc sputtered films exhibited the average surface roughness R_a less than 1.0 nm and a T_c zero value of 88 K. By using the dc-sputtered La-YBCO films, a multilayer structure of SrSnO₃/La-YBCO/SrSnO₃/La-YBCO on MgO substrate with R_a below 2.0 nm was obtained. Interface-modified ramp-edge junctions with La_0.2-Yb_0.9Ba_1.9Cu₃O_x (La-YbBCO) counter electrodes have been fabricated by using this multilayer structure with dc-sputtered films. The fabricated junctions exhibited RSJ-type I-V characteristics with I_cR_n products of about 3 mV at 4.2 K. We also obtained a 1-σ I_c spread of 8% for a 1000-junction series-array. The sheet inductance values at 4.2 K for the base and counter electrodes on La-YBCO ground planes were 0.8 pH and 0.7 pH per square, respectively. Operation of several types of elementary SFQ circuits has been successfully demonstrated by using this multilayer structure.},
keywords={},
doi={10.1093/ietele/e88-c.2.208},
ISSN={},
month={February},}

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TY - JOUR
TI - Development of Thin Film Multilayer Structures with Smooth Surfaces for HTS SFQ Circuits
T2 - IEICE TRANSACTIONS on Electronics
SP - 208
EP - 215
AU - Hironori WAKANA
AU - Seiji ADACHI
AU - Ai KAMITANI
AU - Kouhei NAKAYAMA
AU - Yoshihiro ISHIMARU
AU - Yoshinobu TARUTANI
AU - Keiichi TANABE
PY - 2005
DO - 10.1093/ietele/e88-c.2.208
JO - IEICE TRANSACTIONS on Electronics
SN -
VL - E88-C
IS - 2
JA - IEICE TRANSACTIONS on Electronics
Y1 - February 2005
AB - We have fabricated a multilayer structure for single flux quantum (SFQ) circuit application using a high-temperature superconductor (HTS). La_0.2-Y_0.9Ba_1.9Cu₃O_x (La-YBCO) base electrode layers were prepared by a dc or rf magnetron sputtering method. The reproducibility of film quality for dc-sputtered La-YBCO films was better than that for rf-sputtered films, and the dc sputtered films exhibited the average surface roughness R_a less than 1.0 nm and a T_c zero value of 88 K. By using the dc-sputtered La-YBCO films, a multilayer structure of SrSnO₃/La-YBCO/SrSnO₃/La-YBCO on MgO substrate with R_a below 2.0 nm was obtained. Interface-modified ramp-edge junctions with La_0.2-Yb_0.9Ba_1.9Cu₃O_x (La-YbBCO) counter electrodes have been fabricated by using this multilayer structure with dc-sputtered films. The fabricated junctions exhibited RSJ-type I-V characteristics with I_cR_n products of about 3 mV at 4.2 K. We also obtained a 1-σ I_c spread of 8% for a 1000-junction series-array. The sheet inductance values at 4.2 K for the base and counter electrodes on La-YBCO ground planes were 0.8 pH and 0.7 pH per square, respectively. Operation of several types of elementary SFQ circuits has been successfully demonstrated by using this multilayer structure.
ER -