MASS SPECTROSCOPIC STUDIES ON OUTGROWTH PRECIPITATES IN LASER-ABLATED FILMS

We have observed the velocity distribution of ionic species in the plume by a mass spectrometer during laser ablation of Y1Ba2Cu3Ox target. The velocity distribution of Cu+ ions is strongly influenced by ambient oxygen pressure. As an oxygen pressure is raised, the velocity distribution of Cu+ ions becomes narrows up to 2x10(-2) Torr, and then becomes broad again at higher pressures. This change in the velocity distribution reflects the conversion of the supersonic expansion into the thermal equilibrium flow of the ejected species in the plume. The surface morphology of films is crucially dependent on the velocity distributions.