Structural Changes and Transport Properties of YBa₂Cu₃O₇ Locally Modified by a He⁺ Focused Ion Beam

Irradiation of a material with ions can cause various defects that can lead to structural phase transitions and the modification of the material's properties. Here we study the irradiation of epitaxially grown thin films of the high-temperature superconductor YBa₂Cu₃O₇ with 30 keV ${\mathrm{He}}^{+}$ ions which leads to the expansion of the crystal lattice, degradation of superconducting properties, and eventual transition to an insulator. Fabrication of such insulating regions with a focused He-Ion beam with a spot size of $\sim 10$  nm is a powerful technique for fabrication of superconducting nano-devices. Using low-temperature resistivity measurements, diffraction with a nanofocused X-ray beam and atomic force microscopy, we investigated how the structure and the electric transport properties of YBa₂Cu₃O₇ depend on the irradiation dose in a range 10-100 ions/nm² and on the lateral size of the irradiated area in a range 30-5000 nm.