Formation of thin superconducting films by the laser processing method

We have prepared thin films of Y-Ba-Cu-O superconductors using a pulsed laser evaporation technique. Thin films were formed on (100) Si, (100) MgO, (1̄102) sapphire, (100) SrTiO₃, and amorphous SiO₂ substrates using a XeCl excimer laser (λ=0.308 μm, τ=45×10^-9 s). The depositions were done in an ultrahigh vacuum chamber with pressure of about 10^-6 Torr during thin-film formation. The deposition by pulsed nanosecond laser irradiation results in stoichiometry close to that of the target. The thickness of the film was controlled by varying the pulse energy density and the number of pulses. The substrate temperature was kept at 470°C during deposition. Subsequent annealing treatments were carried out at 900 and 650°C in oxygen atmosphere to recover the superconducting properties of these thin films. The resistance of these films was measured as a function of temperature using the four-point probe method. These thin films were analyzed using cross-section transmission electron microscopy, Rutherford backscattering spectrometry, and channeling techniques. The variation in the oxygen content and the interdiffusion of species into the substrate during subsequent annealing treatments are discussed.