18O isotopic tracer studies of the laser ablation of Bi2Sr2Ca1Cu2O8

The mechanisms of oxygen incorporation into the growing film during the pulsed laser ablation of a Bi2Sr2Ca1Cu2O8 target have been investigated by the complementary use of 18O isotopic tracing techniques and nuclear microanalysis. Roughly 45% of the oxygen present in the film comes from the ambient gas and the remaining part is directly incorporated from the target. Moreover, oxygen is only incorporated in the Bi2Sr2Ca2Cu1O8 films during the growth period (i.e., laser pulse), since neither oxidation nor oxygen exchange occur during the time interval between successive laser pulses. It is also shown that the main mechanism of oxygen incorporation corresponds to the dissociation of molecular oxygen adsorbed at the surface, leading to the formation of very reactive atomic oxygen which is further injected in the films. This oxygen dissociation is the result of the interaction with the high flux of species coming from the target and reaching the film surface during each laser ablation pulse.