Laser surface interaction during and after deposition of thin oxide films

Abstract

Thin films of PZT (Pb(Zr 0.54Ti 0.46)O 3) were deposited by KrF and XeCl excimer laser ablation onto platinated silicon wafers ( Si Pt ) and yttrium stabilized zirconia (YSZ) covered with YBa 2Cu 3O 7− x (YSZ/YBCO). The substrate temperature ( T s) ranged from 240 to 720°C and the substrate surface was optionally activated by excimer laser irradiation (ArF, KrF) during deposition. On Si Pt substrates PZT showed permittivity values of ϵ≤200 only, with ArF laser activation (20 mJ/cm 2, T s = 360°C) ϵ = 360. On YSZ/YBCO samples, ferroelectric PZT of dominantly perovskite crystal structure was obtained at T s = 500–700°C with ϵ≤ 750. With surface activation (ArF: ≤ 35 mJ/cm 2, KrF: ≤ 85 mJ/cm 2) at T s = 350–500°C PZT showed ϵ = 500–1200. In de SQUIDs one Josephson junction was selectively heated above T c by Ar + laser irradiation to measure the critical current of the second junction individually. At high Ar + laser intensity O 2 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 AuO x , PtO x , and AuAgO x showed O 2 effusion upon Ar + laser irradiation depending on the laser intensity. The electrical contact resistance decreased from 10 −2 Ω cm 2 to 5 × 10 −7 Ω cm 2 when converting AuAgO x to AuAg. The superconductivity in YBCO under the laser modified contact was completely preserved.