Abstract:
The optical properties of single-crystal thin films of Sr$_{0.61}$Ba$_{0.39}$Nb$_2$O$_6$, with a thickness of $\sim$ 646 nm, synthesized on MgO(001) substrates using high-frequency cathode sputtering in an oxygen atmosphere, have been studied using spectrophotometry in the spectral range 200–1000 nm and at temperatures between 299.15 K and 393.15 K. It has been observed that the edge of the optical absorption in the transmission spectra of the Sr$_{0.61}$Ba$_{0.39}$Nb$_2$O$_6$/MgO system shifts towards the long-wavelength region with increasing temperature. The dispersion dependences of the refractive index $(n)$ and extinction coefficient $(k)$ of the film have been calculated at fixed temperatures. It has been shown that the film has slightly lower values of these optical parameters compared to the single-crystal Sr$_{0.61}$Ba$_{0.39}$Nb$_2$O$_6$ material. The dispersion of $n(\lambda)$ has been interpreted within the framework of the individual dipole oscillator model and approximated using the Cauchy relation. The results obtained in this study indicate the stability of the optical properties of Sr$_{0.61}$Ba$_{0.39}$Nb$_2$O$_6$ heterostructures grown on MgO substrates over a given wavelength range within the specified temperature range.
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