Surface planarization and masked ion-beam structuring of YBa2Cu3O7 thin films

Surface planarization and masked ion-beam structuring (MIBS) of high-Tc superconducting (HTS) YBa2Cu3O7-δ (YBCO) thin films grown by pulsed-laser deposition (PLD) method is reported. Chemical–mechanical polishing, plasma etching, and oxygen annealing of YBCO films strongly reduce the particulate density (~ 10–2 ×) and surface roughness (~ 10–1 ×) of as-grown PLD layers. The resistivity, critical temperature Tc ≈ 90 K and critical current density Jc (77 K) > 1 MA/cm2 of films are not deteriorated by the planarization procedure. The YBCO films are modified and patterned by irradiation with He+ ions of 75 keV energy. Superconducting tracks patterned by MIBS without removal of HTS material and, for comparison, by wet-chemical etching show same Tc and Jc(T) values. Different micro- and nano-patterns are produced in parallel on planarized films. The size of irradiated pattern depends on the mask employed for beam shaping and features smaller than 70 nm are achieved.