Laser deposition of YBa2Cu3O7 films on MgO(100) at 100 mm target-substrate distance and oxygen pressures below 0.1 mbar

A pulsed KrF excimer laser is used to deposit YBa2Cu3O7 films on MgO(100). We investigate the influence of oxygen pressure and substrate temperature in the range of 0.03 to 0.12 mbar and 732 to 778°C, respectively. The film quality is characterized by electrical properties, homogeneity, orientation and morphology. One way to improve the homogeneity is to increase the target-substrate distance. In order to maintain smooth surfaces, it is necessary to decrease the oxygen pressure until a substrate position at the end of the plasma plume is achieved. When the pressure is reduced below 0.1 mbar a sensitive dependence of the orientation on the oxygen pressure is observed, i.e. a smaller offer of oxidized elements seems to favour a-axis orientation. Optimum deposition parameters for the target-substrate distance of 100 mm are an oxygen pressure of 0.07 mbar and a substrate temperature of 765°C.