Ramp Josephson junctions based on NdBa2Cu3O7-δ electrodes and PrBa2Cu3O7-δ barriers

Författare: Mikael Sjöstrand; [2006]

Nyckelord: TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; PBCO; high temperature; superconducting device; ramp Josephson junction; NBCO; pulsed laser deposition; thin film;

Sammanfattning: We report on smooth high quality c-axis orientedNdBa2Cu3O7-δ (NBCO) superconducting thin filmsgrown on (001) SrTiO3 substrates using pulsed laser deposition.The transition temperature of these NBCO films was around 89.5 Kand the root-mean-square (RMS) surface roughness was 0.75 nm for150 nm thick films.Insulating layers ofPrBa2Cu3O7-δ/SrTiO3/PrBa2Cu3O7-δgrown in-situ on top of the NBCOsuperconducting films, result in superconductor/insulatormultilayers of about 400 nm in total thickness and an RMS surfaceroughness of 2.4 nm.Smooth ramps with angles of about 20° are patterned in themultilayers using a photoresist reflow process and Ar+-ionmilling.A study of the conduction mechanism inPrBa2Cu3O7-δ with different Ga doping levels hasbeen done. We found that the conductivity was governed by variablerange hopping conductivity at higher temperatures(>200 K). At lower temperatures (

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