Low-energy (40 keV) proton irradiation of YBa ₂ Cu ₃ O _{7− x} thin films: Micro-Raman characterization and electrical transport properties

Abstract

To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiated YBa 2 Cu 3 O 7−x (YBCO) thin films are carried out. From micro-Raman spectroscopy and x-ray diffraction studies, the main component of proton-radiation-induced defects is found to be the partial transition of superconducting orthorhombic phase to the semiconducting tetragonal phase and non-superconducting secondary phase. The results indicate that the defects induced in the conducting CuO 2 planes, such as increased oxygen vacancies and interstitials, can result in an increase in the resistivity but a decrease in the transition temperature T C with the increase in the fluence of proton irradiation, which is confirmed in the electrical transport measurements. Especially, zero-resistance temperature T C0 is not observed at a fluence of 10 15 p/cm 2 . Furthermore, the variation of activation energy U 0 can be explained by the plastic-flux creep theory, which indicates that the plastic deformation and entanglement of vortices in a weakly pinned vortex liquid are caused by disorders of point-like defects. Point-like disorders are demonstrated to be the main contribution to the low-energy proton radiation damage in YBCO thin films. These disorders are likely to cause flux creep by thermally assisted flux flow, which may increase noise and reduce the precision of superconducting devices.

Radiation effects in high-temperature YBa2Cu3O7-x superconducting thin films with low-energy protons for space radiation environments

“…This is owing to the displacement energy of oxygen atoms in the Cu-O chains is much lower than that of oxygen atoms in the CuO 2 planes [31]. But it has been proved that a decrease in the transition temperature T c with the increase in the fluence of proton irradiation after the fluence of 1×10 14 p cm −2 , which indicates that oxygen defects in CuO 2 planes with cumulative irradiation [32]. Especially, there is no observed zero-resistance after a fluence of 1×10 15 p cm −2 [32].…”

Lattice deformation in epitaxial Fe3O4 films on MgO substrates studied by polarized Raman spectroscopy*

“…Raman spectroscopy is a powerful tool to probe the microstructure of thin films and its relationship with other physical properties of oxides. [15,16] In past decades, Raman spectroscopy has been widely employed to study the structure of Fe 3 O 4 films. [8,9,17] films.…”

An ion-beam engineered microstructure for high-performance superconducting films

“…Studies on proton irradiation have already been demonstrated to create random point defects [125][177], which can create c-axis peak enhancements at low temperatures and high magnetic field regimes [116] (dE/dx) can be compared to previously experimentally established graphs [123] that display the ranges of energy loss values required to create defects of different morphologies. By utilising this information, we can identify the specific energy range required for heavy ion irradiation to create a defect with the desired morphology.…”

“…By utilising this information, we can identify the specific energy range required for heavy ion irradiation to create a defect with the desired morphology. However, in proton irradiation investigation, the information regarding the type of defects it can create is not required as previous research has shown that irradiation using protons creates point defects [125].…”

“…Figure8-4. Angle dependence of the critical current at temperatures ranging from 20 K to 77 K and applied magnetic fields ranging from 1 T to 8 T of the pristine sample, a sample irradiated using 125 MeV silver ions to a fluence of 2×10 11 ions/cm 2 , a proton irradiated sample to a fluence of 1.3×1016 ions/cm 2 and a sample with a combined pinning landscape created by125 MeV silver ions at the same fluence of 2×10 11 ions/cm 2 and protons at the same fluence of 1.3×1016 ions/cm 2 . ...............…”