Microwave devices using YBa2Cu3O7-δ films made by pulsed laser deposition

High-quality oriented thin films of YBa₂Cu₃O _7-δ with transition temperatures >88 K and critical current densities (at 77 K, zero magnetic field) >10⁶ A/cm ² have been produced by pulsed laser deposition on ⟨100⟩ MgO and LaAlO₃ substrates. The microwave surface resistance (R_s) was measured between 20 K and 120 K at 36 GHz by a copper cavity end-wall-replacement technique. R_s measurements show consistently sharp transitions having high critical temperature onsets with low residual surface resistances (<10 mΩ at 36 GHz and 77 K). Microwave devices fabricated from films on MgO have included an X-band modified five-pole Chebyshev filter with an insertion loss of ~0.8 dB at 77 K. Irradiation of unpatterned films on LaAlO₃ with 2-MeV H⁺ ions at a fluence increment of 10¹⁶/cm² resulted in only a small shift (~2 K) in the 36-GHz microwave transition temperature. No accompanying degradation in the residual surface resistance was observed within the sensitivity of the measurement