Influence of the radiofrequency plasma beam addition on the properties of pulsed laser deposited films

摘要

The modifications of microstructure and of physical properties induced by the use of an additional radiofrequency beam discharge during the pulsed laser deposition (PLD) process has been investigated for different classes of materials. The materials concerned are piezoelectric oxides (ZnO), gate dielectric oxides (ZrO_2), ferroelectric oxides (BaTiO_3), ferroelectric relaxors (Pb_(1-x)La_x)(Zr_(0.65)Ti_(0.33))O_3 (PLZT) with variable La contents, respectively. Using a special configuration of the radio frequency discharge, a beam of excited and/or ionized oxygen species was produced and directed towards the substrate. RF plasma excited species identified in the spectra and impinging the substrate surface are very reactive at the surface with metals ions, neutral and sub-oxides which arrive from the laser plasma, with respect to discharge-off conditions. Thus, the RF plasma contribution is very important between the laser pulses, especially in the early after-pulse stages, when the surface of the fresh deposited film is not completely stabilized. A parametric study has been performed to evidence the corroborative effects induced by RF beam and other parameters as laser wavelength (265 nm, 355 nm, 530 nm and 1060 nm), laser fluence (2-25 J/cm~2), oxygen pressure (0.2-0.8 mbar), substrate temperature (RT-650℃) on the composition and crystallinity and on dielectric and ferroelectric properties.