In-situ monitoring of the deposition of superconducting thin films by FT-IR and mass spectrometry

Superconducting thin films were produced by pulsed laser ablation of a YBa₂Cu₃O_7-x pressed pellet target, using a Nd:YAG laser operating at 1060, 532, 355, and 266 nm wavelengths. Various laser fluences from 20 to 0.5 J/cm² were used in order to study the effect of laser fluence and laser wavelength on film quality. Optimum laser fluence was 3 J/cm³ for all wavelengths, while the best films were produced at shorter wavelengths. Fourier transform infrared (FT-IR) reflectance spectroscopy was used in-situ to observe the film deposition process. Quadrupole mass spectra were obtained independently, with the same laser fluences and wavelengths used previously. Typically, higher fluences produced fewer metal oxide ions, and stoichiometry was not preserved by the ablated positive ions. More Ba⁺ ions than Y⁺ or Cu⁺ ions were observed. No CuO⁺ ions were detected. SEM photographs revealed that longer wavelengths produced larger particle sizes in the films, and higher fluences produced the same results.