Raman characterization of strain in epitaxial Cr2O3 films on sapphire

Ahti Niilisk 1Martti Pärs 1Ilmo Sildos 1Rainer Pärna 1,2Aivar Tarre 1Arnold Rosental 1,2Jaan Aarik 1

1. Institute of Physics, University of Tartu, Riia str. 142, Tartu 51014, Estonia
2. Estonian Nanotechnology Competence Center, Riia str. 142, Tartu 51014, Estonia

Abstract

By using atomic layer deposition from CrO2Cl2 and CH3OH at 420 °C, chromia (eskolaite α-Cr2O3) was epitaxially grown on c- and r-cut sapphire. Also, the material was grown in the polycrystalline form on fused silica. Micro-Raman spectra of the films excited with 532 nm laser radiation were measured. Five Raman bands are expected in the spectrum of α-Cr2O3, including the most intensive one (A1g) at about 550 cm-1. We demonstrated that the position of the latter band depended on the substrate: in the sapphire case the band was greatly blue shifted with respect to its position in the silica case. The shift was used for the evaluation of the strain in the epitaxial chromia. The evaluation gave a hydrostatic equivalent stress of 5.9 GPa for the thinnest (about 4 nm) film on c-cut sapphire. With the thickness increase up to 210 nm, the stress in the films decreased down to 1.9 GPa. The compressive stress was observed also in the films grown on r-cut sapphire.

 

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium C, by Ahti Niilisk
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-06-27 17:36
Revised:   2009-06-07 00:44