The structural, thermal and superconducting properties of Pb nanoparticles (NPs) embedded in a single crystalline epitaxial Al film, synthesized by high-fluence implantation and subsequent annealing, have been experimentally investigated. Various implantation fluences and temperatures, annealing durations and temperatures were used to optimally tune the size (average diameter ranging from 5 to 20 nm) and size distribution of the NPs. The structural properties were characterized by Rutherford backscattering spectrometry (RBS), and x-ray diffraction (XRD). It has been shown that after implantation, fcc-structured strain-free Pb NPs, which were epitaxially oriented with the Al substrate, were formed. The different scaling laws of the average radius <R> of Pb NPs with the implantation fluence f could be used to distinguish three size evolution regimes during the ion implantation at room temperature, which are supersaturation and nucleation, interface kinetics limited growth (<R>∝f ), and diffusion limited growth ( <R>²∝f ) regimes, respectively.

The melting and solidification behavior of the Pb NPs has been studied by high temperature XRD. Large superheating and supercooling of the Pb NPs were found during melting-solidification cycles. The width of the hysteresis, which is drastically dependent on the size of Pb NPs, is due to a contribution from the low energy epitaxial interfaces and a contribution from the finite size effect.

The superconducting critical temperature of the implanted Al layer increases with the Pb NPs volume ratio, which can be explained by the superconducting proximity effect. Our experimental data fit well with the strong-coupling limited theory in the Cooper limit.