Radiation-induced phase transition in a film of niobium-tin solid solution

A 5-$\mu$m-thick film of a niobium-tin solid solution (18.3 at% Sn) grown by ion-plasma sputtering with subsequent codeposition of ultrafine metal particles is irradiated by a fast proton flux with a fluence of 10$^{19}p^+$/cm$^2$. X-ray diffraction analysis carried out using Cu$K_\alpha$ ($\lambda$ = 0.154178 nm), Co$K_\alpha$ ($\lambda$ = 0.179021 nm), and Mo$K_\alpha$ ($\lambda$ = 0.071069 nm) radiations shows the presence of a radiation-induced stannide niobium (Nb$_3$Sn) phase in the region of proton energy dissipation (at a depth of 2.5 $\mu$m from the surface of the solid solution film). It is found that at the end of the particle range, nonlocal interaction between the protons and the concentrated matrix solid solution takes place. When interacting with the supersaturated solid solution, a bombarding particle covers a tangible area of the solution, so that an intermetallic phase greater than critical in size nucleates. The feasibility is demonstrated of using a fast particle flux to produce an intermetallic (superconducting) phase inside a solid solution layer with a composition close to the stoichiometric composition of the intermetallic.