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Influence of oxygen partial pressure on the composition and orientation of stronium-doped lead zirconate titanate thin films

Sharath Sriram 1Madhu Bhaskaran 1Johan Du Plessis 2Ken T. Short 3Anthony S. Holland 1

1. RMIT University, Sch. of Elec. and Comp. Engg., Microelectronics and Materials Technology Centre (RMIT), GPO Box 2476V, Melbourne, Victoria, Melbourne 3001, Australia
2. RMIT University, School of Applied Sciences (RMIT), GPO Box 2476V, Melbourne, Victoria, Melbourne 3001, Australia
3. Australian Nuclear Science and Technology Organisation, Institute of Material Science and Engg. (ANSTO), PMB 1, Menai, New South Wales, Sydney 2234, Australia

Abstract

The influence of oxygen partial pressure during the deposition of ferroelectric strontium-doped lead zirconate titanate thin films is reported. The thin films have been deposited by RF magnetron sputtering in an atmosphere of high purity argon and oxygen (in the ratio of 9:1); on platinum-coated silicon substrates (heated to 650 ÂșC). The post deposition cooling rate has been identified to influence the extent of the desired perovskite orientation of the thin films; with slower cooling rates resulting in more pronounced perovskite orientation. The influence of oxygen partial pressure is studied to understand the manner in which the stoichiometry of the thin films is modified, and to understand the influence of stoichiometry on the perovskite orientation.

This paper reports on the results obtained from films deposited at oxygen partial pressures of 1, 2, 3, 4, and 5 mTorr. The thin films have been studied using a combination of X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (GA-XRD), atomic force microscopy (AFM), and optical characterisation. XPS analysis highlights the marked influence of variations in oxygen pressure during sputtering, observed by variations in oxygen concentration in the thin films, and in some cases by the undesirable decrease in lead concentration in the thin films. GA-XRD is used to study the relative variations in perovskite peak intensities, and has been used to determine the deposition conditions to attain the optimal combination of stoichiometry and orientation. AFM scans show a trend of increasing surface roughness with increase in oxygen partial pressure, and also variations in grain structure and size. Films have also been optically characterized by refractive index measurements using a prism coupler. The films exhibit a high refractive index of approximately 2.3 (varying with oxygen partial pressure) at 633 nm.

 

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium J, by Sharath Sriram
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-04 10:31
Revised:   2009-06-07 00:44