The interaction of ambient background gas with a plume formed in pulsed laser deposition

The propagation of KrF excimer laser-produced plasmas from Pb(Zr0.52Ti0.48)O-3 has been studied with emphasis on topics relevant to the interaction of a plume with ambient gas in oxide film growth by pulsed laser deposition. A gated CCD was employed to investigate the overall shape and propagation of the laser plasma in different background gases. It is found that the plume image in both 20 Pa O-2 and Ar is spherical. With increasing O-2 pressure to 60 Pa, the plumes are prolonged along the target normal direction and suppressed in the direction parallel to the target surface. Above 60 Pa, the plumes are suppressed along both directions. When the ambient gas is Ar, the changes of the plumes are contradictious. The similarity of plume shape in 20 Pa O-2 and Ar has been interpreted as that the interaction of ablated species with ambient gas is mainly elastic. The differences are thought to be due to the interaction of ablated species with ambient gas, which is reactive in O-2 and elastic in Ar. It was proposed that the elastic scattering of ablated species by background gas leads to the nonstoichiometry of the deposited film, while the reactive collision of ablated species with ambient gas is favorable to reduce the nonstoichiometry and to enhance the oxygen incorporation in the film. It was proposed that the propagation of the ablated species can be divided into three regimes.