[Paper Review] High-quality YBa2Cu3O7-x nanobridges fabricated by FIB etching

Matvey Lyatti, Alexey Savenko+2 more|arXiv (Cornell University)|Mar 10, 2016

Physics of Superconductivity and Magnetism6 references3 citations

TL;DR

This paper presents a cold nanopatterning technique using a removable protection layer to fabricate high-quality YBa2Cu3O7-x nanobridges via focused ion beam (FIB) etching. The method preserves the superconducting properties of ultra-thin films, achieving critical current densities up to 125 MA/cm² at 8 K and maintaining nearly identical critical temperature and transition width down to 150 nm bridge width.

ABSTRACT

Nanostructuring of YBa2Cu3O7-x films is a challenging task on a way to the high-quality YBa2Cu3O7-x nanodevices because of the sensitivity of YBa2Cu3O7-x thin films to the patterning process. In this work we report on a cold nanopatterning procedure used for the structuring of the ultra-thin YBa2Cu3O7-x films by focused ion beam etching with a specially developed protection layer, which can be easily removed after the patterning process without any damage to the ultra-thin YBa2Cu3O7-x film. High-quality ultra-thin YBa2Cu3O7-x nanobridges, fabricated with this nanopatterning procedure, demonstrated nearly the same values of the critical temperature and the transition width as an original film for bridge widths down to 150 nm. High critical current densities up to 125 MA/cm2 have been achieved at T = 8 K. The observed dependence of the critical current density on the width and the thickness of nanobridges was consistent with the edge barrier model.

Motivation & Objective

• To develop a reliable nanopatterning method for ultra-thin YBa2Cu3O7-x films without degrading their superconducting properties.
• To address the challenge of film sensitivity during FIB etching, which often damages the superconducting layer.
• To enable the fabrication of high-quality nanobridges with sub-200 nm widths for nanoscale superconducting devices.
• To achieve high critical current densities while maintaining sharp superconducting transition characteristics.

Proposed method

• A specially designed removable protection layer is applied before FIB etching to shield the ultra-thin YBa2Cu3O7-x film from ion beam damage.
• The nanopatterning is performed at low temperature (cold FIB) to minimize thermal and ion-induced degradation.
• After patterning, the protection layer is completely removed without damaging the underlying YBa2Cu3O7-x film.
• The process enables precise fabrication of nanobridges with widths down to 150 nm.
• The critical temperature and transition width of the nanobridges are measured and compared to the original film to assess preservation of superconducting quality.
• The critical current density is measured as a function of bridge width and thickness to test consistency with the edge barrier model.

Experimental results

Research questions

• RQ1 Can a cold FIB nanopatterning process with a removable protection layer preserve the superconducting properties of ultra-thin YBa2Cu3O7-x films?
• RQ2 To what extent does the critical temperature and transition width of nanobridges match those of the original film after FIB etching?
• RQ3 What critical current densities can be achieved in YBa2Cu3O7-x nanobridges with widths down to 150 nm using this method?
• RQ4 Does the observed critical current density dependence on width and thickness align with the edge barrier model?

Key findings

• The fabricated YBa2Cu3O7-x nanobridges maintained nearly identical critical temperature and transition width compared to the original film, even at widths as small as 150 nm.
• Critical current densities as high as 125 MA/cm² were achieved at 8 K, indicating excellent superconducting performance.
• The dependence of critical current density on bridge width and thickness was consistent with the edge barrier model.
• The protection layer was successfully removed after patterning without causing any detectable damage to the YBa2Cu3O7-x film.
• The method enables high-quality nanodevice fabrication from ultra-thin YBa2Cu3O7-x films, overcoming the challenges of ion beam sensitivity.
• The results demonstrate the feasibility of producing sub-200 nm superconducting nanobridges with preserved superconducting integrity.