LASER DEPOSITION OF YBA2CU3O7 FILMS ON MGO(100) AT 100MM TARGET-SUBSTRATE DISTANCE AND OXYGEN PRESSURES BELOW 0.1MBAR

A pulsed KrF excimer laser is used to deposit YBa(2)Cn(3)O(7) films on MgO(100). We investigate the influence of oxygen pressure and substra te temperature in the range of 0.03 to 0.12 mbar and 732 to 778 degree s C, respectively. The film quality is characterized by electrical pro perties, homogeneity, orientation and morphology, One way to improve t he homogeneity is to increase the target-substrate distance. In order to maintain smooth surfaces, it is necessary to decrease the oxygen pr essure until a substrate position at the end of the plasma plume is ac hieved. When the pressure is reduced below 0.1 mbar a sensitive depend ence of the orientation on the oxygen pressure is observed, i.e. a sma ller offer of oxidized elements seems to favour a-axis orientation. Op timum deposition parameters for the target-substrate distance of 100 m m are an oxygen pressure of 0.07 mbar and a substrate temperature of 7 65 degrees C.