Laser surface interaction during and after deposition of thin oxide films

Thin films of PZT (Pb(Zr0.54Ti0.46)O3) were deposited by KrF and XeCl excimer laser ablation onto platinated silicon wafers (SiPt) and yttrium stabilized zirconia (YSZ) covered with YBa2Cu3O7−x (YSZ/YBCO). The substrate temperature (Ts) ranged from 240 to 720°C and the substrate surface was optionally activated by excimer laser irradiation (ArF, KrF) during deposition. On SiPt substrates PZT showed permittivity values of ϵ≤200 only, with ArF laser activation (20 mJ/cm2, Ts = 360°C) ϵ = 360. On YSZ/YBCO samples, ferroelectric PZT of dominantly perovskite crystal structure was obtained at Ts = 500–700°C with ϵ≤ 750. With surface activation (ArF: ≤ 35 mJ/cm2, KrF: ≤ 85 mJ/cm2) at Ts = 350–500°C PZT showed ϵ = 500–1200. In de SQUIDs one Josephson junction was selectively heated above Tc by Ar+ laser irradiation to measure the critical current of the second junction individually. At high Ar+ laser intensity O2 effusion from YBCO was used to narrow the junction width in steps of 1 μm. The width reduction from 23 to 9 μm in both junctions resulted in a flat baseline of the SQUID and an increase of the voltage modulation amplitude from 8 to 12 μV. Passivation layers for YBCO consisting of AuOx, PtOx, and AuAgOx showed O2 effusion upon Ar+ laser irradiation depending on the laser intensity. The electrical contact resistance decreased from 10−2 Ω cm2 to 5 × 10−7 Ω cm2 when converting AuAgOx to AuAg. The superconductivity in YBCO under the laser modified contact was completely preserved.