We investigated the effect of 0.6 MeV proton irradiation on the superconducting and normal-state properties of thin-film ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ superconductors. A thin-film YBCO superconductor (≈567 nm thick) was subject to a series of proton irradiations with a total fluence of $7.6\times {10}^{16}$ ${\mathrm{p}/\mathrm{cm}}^2$. Upon irradiation, $T_c$ was drastically decreased from 89.3 K towards zero with a corresponding increase in the normal-state resistivity above $T_c$. This increase in resistivity, which indicates an increase in defects inside the thin-film sample, can be converted to the dimensionless scattering rate. We found that the relation between $T_c$ and the dimensionless scattering rate obtained during proton irradiation approximates the generalized d-wave Abrikosov–Gor’kov theory better than the previous results obtained from electron irradiations. This is an unexpected result, since the electron irradiation is known to be most effective to suppress superconductivity over other heavier ion irradiations such as proton irradiation. In comparison with the previous irradiation studies, we found that the result can be explained by two facts. First, the dominant defects created by 0.6 MeV protons can be point-like when the implantation depth is much longer than the sample thickness. Second, the presence of defects on all element sites is important to effectively suppress $T_c$.

We investigated the effect of 0.6 MeV proton irradiation on the superconducting and normal state properties of thin-film YBa2Cu3O7−δ superconductors. A thin-film YBCO superconductor (≈ 567 nm thick) was subject to a series of proton irradiations with a total fluence of 7.6×1016p/cm2. Upon irradiation, Tc was drastically decreased from 89.3 K towards zero with a corresponding increase in its normal state resistivity above Tc. This increase in resistivity which indicates the increase of defects inside the thin-film sample can be converted to the dimensionless scattering rate. We found that the relation between Tc and dimensionless scattering rate obtained during proton irradiation approximates the generalized d-wave Abrikosov-Gor’kov theory better than the previous results obtained from electron irradiations. This is an unexpected result since the electron irradiation is known to be most effective to suppress superconductivity over other heavier ion irradiations such as proton irradiation. It suggests that the type of defects created by proton irradiation evolves from cascade defects (in bulk single crystals) to point-like defects (in thin-film single crystals) as the thickness decreases.

The superconducting properties of YBa2Cu3O7−δ thin-films were investigated by conducting 1.7 MeV proton irradiations with a total fluence of 2.64×1017p/cm2. The superconducting critical temperature (Tc) was reduced from 89.4 K to 10.1 K. The experimental procedure was similar to the previous study (0.6 MeV proton irradiation). We compared the effectiveness of Tc suppression by varying the proton energy from 0.6 to 1.7 MeV and found that in general both protons of 1.7 MeV and 0.6 MeV were effective in suppressing the Tc of YBCO. In particular, both results were consistent with the theoretical expectation (extended d-wave AG theory) when the zero-temperature London penetration depth (λ0) = 215 nm is assumed for thin-film YBCO. For heavily irradiated cases (more than 80% Tc suppression), however, 1.7 MeV protons were more effective in suppressing Tc than 0.6 MeV protons. This can be understood by the fact that in thin-film limit, higher energy protons tend to produce less clustered point-defects while lower energy protons tend to create agglomeration of point-defects.

The superconducting properties of YBa₂Cu₃${\mathrm{O}}_{7-\delta }$ thin films were investigated by conducting 1.7 MeV proton irradiations with a total fluence of $2.64\times {10}^{17}$${\mathrm{p}/\mathrm{cm}}^2$. The superconducting critical temperature ($T_c$) was reduced from 89.4 K to 10.1 K. The experimental procedure was similar to a previous study (0.6 MeV proton irradiation). We compared the effectiveness of $T_c$ suppression by varying the proton energy from 0.6 to 1.7 MeV and found that in general both protons of 1.7 MeV and 0.6 MeV were effective in suppressing the $T_c$ of YBCO. In particular, both results were consistent with the theoretical expectation (generalized d-wave AG theory) when a zero-temperature London penetration depth (${\lambda }_0$) = 215 nm is assumed for thin-film YBCO. For heavily irradiated cases (more than 80% $T_c$ suppression), however, 1.7 MeV protons were more effective in suppressing $T_c$ than 0.6 MeV protons. This can be understood by the fact that in the thin-film limit, higher-energy protons tend to produce less clustered point defects while lower-energy protons tend to create agglomeration of point defects.