The Epitaxial Growth Of C-axis Oriented YBa₂Cu₃O₇-δ Films By Pulsed Laser Deposition And The Elimination Of Laser-induced Particles

The YBa2Cu3O 7 ?δ(YBCO) thin films are key materials for various electronic applications, such as Josephson junctions, SQUID, microwave devices, and so on. After decades of intensity studies, there are still few technique difficulties concerning its quality. For instance, there are numerous of laser-induced particles in YBCO films prepared by the pulsed-laser deposition (PLD); and the crystalline orientation of YBCO film is difficult to control. In this paper, we will focus on above two issues.First, PLD is a universal technique to prepare semiconductor, dielectric and high-Tc thin oxide films. However, one typical feature of these films is laser-induced particles on the surface of the film, which were originated from the superheating under the near surface of target. Therefore, we developed a method by inserting a grid-mask of suitable size and location between the substrate and the target to block the large particles. We observe the morphology of the film by the XRD, SEM and AFM measurement methods. The results showed that the final YBCO film is almost free of large-particles and the quality of the film is improved as expected.Second, we studied the phase content and microstructure of c-axis oriented films on the three of single-crystal substrates, i.e. MgO, SrTiO3 and Si, by optimizing of PLD parameters and using of YSZ(yttrium-stabilized zirconia)underlayer (for the Si substrate) and analyzed the mechanism of the relation between the deposition conditions and the quality of phase formation. The films were characterized by the XRD measurement method. After then, the epitaxial growth mechanisms of preferential orientation were discussed through the boundary energy theory and lattice matching theory.