IngentaConnect Effect of Oxygen Plasma on Growth, Structure and Ferroelectric Pr...

Abstract:

Growth of \hbox{SrBi}_{2}\hbox{Ta}_{2}\hbox{O}_{9} (SBT) thin films has been carried out in the presence of \hbox{O}_{2}-plasma created by applying a potential at an auxiliary ring electrode placed near the substrate. Effect of plasma excitation potential and polarity, especially negative polarity, on the formation of a proper SBT phase at 700°C and in modifying crystallite orientation and microstructure of SBT films over (1 1 1) oriented Pt film coated over \hbox{TiO}_{2}/\hbox{SiO}_{2}/\hbox{Si(1\,0\,0)} substrates has been demonstrated. Preferred c-axis orientation of SBT films changes to (a–b) orientation with decrease in plasma excitation potential from -700 to -350 V and eliminates secondary \hbox{Bi}_{2}\hbox{Pt} phase formation even at 600°C Microstructural study show a 2-dimensional large flat c-oriented crystallites formed at -700 V change to small crystallites in conformity with the changed aspect ratio for crystallites in (a–b) plane parallel to film plane. Spectroscopic ellipsometric results are in agreement with the microstructural data. These affects are attributed to \hbox{O}_{2}-ion bombardment during film growth which reduces nucleation barrier for growth of crystallites in (a–b) plane. \hbox{O}_{2}-plasma sustains the cationic species formed by laser ablation, which along with \hbox{O}_{2}^{+} ions, provide necessary activation energy and enhance the oxidation rates required for SBT phase formation even at 700°C. SBT films grown in \hbox{O}_{2}-plasma show enhancement in remnant polarization value from 1.2 to 6.6 C/cm^2 and display ferroelectric properties superior to those formed without plasma. Further \hbox{O}_{2}-plasma eliminates post deposition annealing step for observance of enhanced polarization values. This study shows \hbox{O}_{2}-plasma excitation potential could be exploited as a new process parameter in laser ablation growth of ferroelectric oxide thin films.

Keywords: SBT; plasma; ferroelectric

Language: English

Document Type: Regular paper

Affiliations: 1: Materials Science and Engineering Department, Virginia Polytechnic Institute and State University 213, Holden Hall, Blacksburg, VA 24061-0237

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Effect of Oxygen Plasma on Growth, Structure and Ferroelectric Properties of \hbox{SrBi}_{2}\hbox{Ta}_{2}\hbox{O}_{9} Thin Films Formed by Pulsed Laser Ablation Technique