Laser ablation of oxides: study of the oxygen incorporation by 18O isotopic tracing techniques

The mechanisms of oxygen incorporation in the growing film, during the pulsed laser ablation of a BiSrCaCuO target, have been investigated by the complementary use of 18O isotopic tracing techniques and nuclear microanalysis. During the film growth under 18O ambient, we have shown that only 45% of the oxygen atoms present in the films comes from the ambient gas, the remaining part being directly transferred from the target. Moreover, the oxygen incorporation in the growing film was found to only occur during each laser pulse. Film oxidation, or exchange phenomena between oxygen atoms already fixed in the film, and those coming from the gas do not occur during time interval between laser pulses. It was also shown that the main mechanism of oxygen incorporation in the BiSrCaCuO thin films, corresponds to the dissociation of molecular oxygen adsorbed at the surface, leading to the creation of very reactive atomic oxygen which is further injected in the films. This dissociation being due to the bombardment by the incident energetic (5 to 10 eV) species coming from the target during each laser pulse.