In‐Situ Fabrication of YBa₂Cu₃O_7‐x Superconducting Thin Films Directly on Silicon Substrates with T_c0 > 77K

Abstract

We report in‐situ fabrication of c‐axis textured YBa₂Cu₃O_7‐x superconducting thin films with T_co > 77K on unbuffered silicon substrates by the biased pulsed laser evaporation (PLE) technique in the temperature range of 550‐650°C. At substrate temperatures below 550°C, no c‐axis texturing of the superconducting film was observed. The YBa₂Cu₃O_7‐x superconducting films were fabricated by ablating a bulk YBa₂Cu₃O₇ target by a XeCl excimer laser (λ = 308 nm, τ = 45 × 10^‐9 sec) in a chamber maintained at an oxygen pressure of 0.2 torr . The thickness of the films was varied from 0.3 to 0.5 nm depending on the number of laser pulses. Extensive diffusion was observed in thin films deposited at substrate temperatures above 550°C. However, microstructurally, with increase in the substrate temperature the films exhibited larger grain size and greater degree of c‐axis texturing (measured by the ratio of the (005) and (110) X‐ray diffraction peaks). This was found to give rise to better superconducting properties with T_co exceeding 77 K for YBa₂Cu₃O_7‐x films deposited on Si substrates at 650°C.