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Hydrothermal epitaxy of ferromagnetic TiO2 films

Gregory Goh ,  Kelvin Chan ,  Yuebin Zhang 

Institute of Materials Research and Engineering, Singapore, Singapore

Abstract

TiO2 films are important as self-cleaning and anti-fog optical coatings and as switches and interferometers in optical communication devices because of its large birefringence and favorable photocatalytic properties. More recently, epitaxial TiO2 films doped with ferromagnetic ions have received considerable attention due to their potential as dilute magnetic semiconductors in the field of spin electronics.

In this report, transition metal doped epitaxial anatase films are grown on (001) oriented single crystal SrTiO3 substrates by liquid phase deposition at temperatures as low as 50oC. Besides being a simple and cost effective method of film deposition, the precursor solution can be tailored to provide an oxidizing environment, thus precluding the formation of metal clusters. This is important as it has been argued that the presence of metal clusters in transition metal doped TiO2 films formed by conventional physical vapor deposition techniques is actually responsible for the observed ferromagnetism and not carrier induced.

The epitaxial nature of the as-grown films was confirmed by pole figures while capillary stress induced cracking indicates that the film is nanoporous. XPS and SIMS show the presence of the dopant ions throughout the films and absorption measurements suggest that the dopants have substituted Ti4+ from its octahedral environment. The films are ferromagnetic, as determined by AGM and SQUID, and the effect of heat treatments on the chemistry of the film and its ferromagnetism is reported.

 

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Presentation: Oral at E-MRS Fall Meeting 2007, Symposium B, by Gregory Goh
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-11 08:54
Revised:   2009-06-07 00:44