Optical Nanoscopy of High TcCuprate Nanoconstriction Devices Patterned by Helium Ion Beams.
Helium ion beams (HIB) focused to subnanometer scales have emerged as powerful tools for high-resolution imaging as well as nanoscale lithography, ion milling, or deposition. Quantifying irradiation effects is an essential step toward reliable device fabrication, but most of the depth profiling information is provided by computer simulations rather than the experiment. Here, we demonstrate the use of atomic force microscopy (AFM) combined with scanning near-field optical microscopy (SNOM) to provide three-dimensional (3D) dielectric characterization of high-temperature superconductor devices fabricated by HIB. By imaging the infrared dielectric response obtained from light demodulation at multiple harmonics of the AFM tapping frequency, we find that amorphization caused by the nominally 0.5 nm HIB extends throughout the entire 26.5 nm thickness of the cuprate film and by ∼500 nm laterally. This unexpectedly widespread damage in morphology and electronic structure can be attributed to a helium depth distribution substantially modified by the internal device interfaces. Our study introduces AFM-SNOM as a quantitative tomographic technique for noninvasive 3D characterization of irradiation damage in a wide variety of nanoscale devices.
Department of Applied Physics, Yale University , New Haven, Connecticut 06511, United States.|Energy Sciences Institute, Yale University , West Haven, Connecticut 06516, United States.
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0000-0002-3233-0990
A
Gozar
Department of Physics, Harvard University , Cambridge, Massachusetts 02138, United States.|Brookhaven National Laboratory , Upton, New York 11973, United States.
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NE
Litombe
Department of Physics, Harvard University , Cambridge, Massachusetts 02138, United States.
Jennifer E
JE
Hoffman
Department of Applied Physics, Yale University , New Haven, Connecticut 06511, United States.|Energy Sciences Institute, Yale University , West Haven, Connecticut 06516, United States.|Brookhaven National Laboratory , Upton, New York 11973, United States.
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I
Božović
Helium ion scattering and microscopy; dielectric nanotomography; nanopatterning; near-field microscopy; superconducting electronics