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Inducing superconductivity at a nanoscale: photodoping with a near‐field scanning optical microscope
Author(s) -
Decca R. S.,
Drew H. D.,
Maiorov B.,
Guimpel J.,
Osquiguil E. J.
Publication year - 1999
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1046/j.1365-2818.1999.00540.x
Subject(s) - near field scanning optical microscope , josephson effect , superconductivity , materials science , wavelength , thin film , optical microscope , optics , condensed matter physics , optoelectronics , magnetic field , scanning electron microscope , electron , physics , nanotechnology , quantum mechanics
The local modification of an insulating GdBa 2 Cu 3 O 6.5 thin film, made superconducting by illumination with a near‐field scanning optical microscope (NSOM), is reported. A 100‐nm aperture NSOM probe acts as a sub‐wavelength light source of wavelength λ exc = 480–650 nm, locally generating photocarriers in an otherwise insulating GdBa 2 –Cu 3 O 6.5 thin film. Of the photogenerated electron–hole pairs, electrons are trapped in the crystallographic lattice, defining an electrostatic confining potential to enable the holes to move. Reflectance measurements at λ = 1.55 μm at room temperature show that photocarriers can be induced and constrained to move on a ≈200 nm scale for all investigated λ exc . Photogenerated wires present a superconducting critical temperature T c = 12 K with a critical current density J c = 10 4 A cm −2 . Exploiting the flexibility provided by photodoping through a NSOM probe, a junction was written by photodoping a wire with a narrow (≈ 50 nm) under‐illuminated gap. The strong magnetic field modulation of the critical current provides a clear signature of the existence of a Josephson effect in the junction.