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Temperature dependent optical studies of Ti$_{1-x}$Co$_x$O$_2$

S. Guha·K. Ghosh·J. G. Keeth·S. B. Ogale·S. R. Shinde·J. R. Simpson·H. D. Drew·T. Venkatesan
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Abstract

We present the results of Raman and photoluminescence (PL) studies on epitaxial anatase phase Ti$_{1-x}$Co$_x$O$_2$ films for $x$ = 0-0.07, grown by pulsed laser deposition. The low doped system ($x$=0.01 and 0.02) shows a Curie temperature of ~700 K in the as-grown state. The Raman spectra from the doped and undoped films confirm their anatase phase. The photoluminescence spectrum is characterized by a broad emission from self-trapped excitons (STE) at 2.3 eV at temperatures below 120 K. This peak is characteristic of the anatase-phase TiO$_2$ and shows a small blueshift with increasing doping concentration. In addition to the emission from STE, the Co-doped samples show two emission lines at 2.77 eV and 2.94 eV that are absent in the undoped film indicative of a spin-flip energy.

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S. Guha, K. Ghosh, J. G. Keeth, S. B. Ogale, S. R. Shinde, J. R. Simpson, H. D. Drew, T. Venkatesan. 2003-03-10. Temperature dependent optical studies of Ti$_{1-x}$Co$_x$O$_2$. https://doi.org/10.1063/1.1619212

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