Microstructure characterization of MgO buffered YBa2Cu3O7 on (100) Si during thermal cycling

Scanning electron microscopy (SEM) has been utilized to study the microstru cture of YBa2Cu3O7 superconductor high-temperature thin films under thermal cycling loading. The thin films were deposited on MgO buffered (100) Si su bstrates by the laser ablation and sputtering methods. It is found that the characteristics of the MgO buffer layer have a significant influence on th e thermal fatigue life of the superconductor films. The thickness of YBa2Cu 3O7 thin film plays a key role on the failure of the laser-ablated MgO buff er layer thin film assembly. The development of cracking and spalling, beca use of the coefficient of thermal expansion mismatch, is the leading mechan ism that eventually causes the failure of the buffered MgO thin film system . Various microstructural factors and mechanisms responsible for the failur e of the system are discussed in detail in this paper.