Microstructural and compositional variations in laser-deposited superconducting thin films

Abstract
We have investigated thickness and composition variations in laser‐deposited superconducting thin films and their effects on the microstructure development after subsequent annealing to recover the superconducting properties. Superconducting thin films were deposited on magnesium oxide substrates using a pulsed excimer laser (λ=308 nm, τ=45×109 s). These films were annealed at about 900 °C in helium and oxygen atmospheres followed by slow cooling to room temperature. The forward directed nature of the laser‐induced deposition process in controlling the spatial variation in thickness of the film was examined using gas dynamics of the laser generated plasma. The compositional variation as a function of spatial distance was determined by Rutherford backscattering spectrometry. Correlation of the presence of different phases with the average composition in the film was done using transmission electron microscopy combined with x‐ray microanalysis techniques. The slight enrichment of yttrium in the film resulted in yttrium‐rich phases in the microstructure.