Mechanism of stoichiometric deposition of volatile elements in multimetal-oxide films prepared by pulsed laser ablation

The mechanism of stoichiometric deposition of volatile elements such as Pb and Bi, which have high vapor pressures, is studied for lead zirconate titanate (PZT) films and bismuth iron garnet (BIG) films, respectively, both prepared by pulsed laser ablation in various ambients and at various temperatures. It is found that O-2 ambient plays a crucial role for the stoichiometric deposition of volatile elements at elevated deposition temperatures. O-2 ambient at a low pressure brings about deficiency of volatile elements. On the other hand, if O-2 ambient at a high pressure is employed, the composition of volatile elements is preserved because the oxide of the volatile element covers the growing surface. Pb deficiency is observed even. for films deposited at room temperature in a vacuum ambient. This phenomenon is considered to originate from the vaporization of Pb during the flight process. Therefore O-2 ambient with a moderately high pressure is important for stoichiometric deposition. O-2 ambient with excessively high pressure, however, solidifies droplets and brings about severer thickness distribution and/or a rougher surface than those formed at a moderately high pressure.