Oxide thin films deposited by means of laser ablation: structure and properties

Thin films of CeO2 doped with Cu or Nd and Bi2O3 doped with Y were elaborated by Pulsed Laser Deposition technique from sintered Cu-CeO2, Nd-CeO2 and Bi2O3 or Y- Bi2O3 targets. Two types of laser ablation equipment have been applied: one worked with a KrF excimer and second with an Q-switched Nd:YAG. The films were deposited on (100) and (110) oriented Si substrates. Scanning and transmission electron microscopy, as well as, x-ray diffraction analyses showed correlation between a copper and neodymium atom fractions and crystalline structure of the (Cu, Ce)O2 and (Nd, Ce)O2 thin films. As demonstrated by x-ray diffraction analysis, with increased quantity of Cu, and Nd the both types of doped CeO2 thin films manufactured by laser ablation show a change of the crystal growth preferential orientation (c-axis- orientation) from strong <111> to a strong <200> ones. In case of pure bismuth oxide deposition, both TEM and X-ray examinations revealed that at applied experimental conditions only &agr; - Bi2O3 (not &dgr; - Bi2O3) crystals were formed during ablation process. Microstructural TEM examinations permitted to show high grain refinement in Y- Bi2O3 thin films. Preliminary measurements show also high level of electrical conductivity in case of this oxide. Due to SiO2 amorphous layer present at the surface of Si substrate, its crystallographic orientation doesn't influence the thin film structure of all analyzed oxides.

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