Last Updated:

20/08/2020 - 16:11

The research article “Investigation of optical properties of Bi12GeO20 sillenite crystals by spectroscopic ellipsometry and Raman spectroscopy”, co-authored by METU member Prof. Nizami Hasanlı, has been published in Ceramics International.

Bi12GeO20 (BGO) compound is one of the fascinating members of sillenites group due to its outstanding photorefractive and photocatalytic characteristics. The present paper aims at investigating optical properties of BGO crystals by means of spectroscopic ellipsometry and Raman spectroscopy measurements. Bi12GeO20 single crystals grown by Czochralski method were structurally characterized by X-ray diffraction (XRD) experiments and the analyses showed that studied crystals have cubic crystalline structure. Raman spectrum exhibited 15 peaks associated with A, E and F modes. Spectroscopic ellipsometry measurement data achieved in the energy region between 1.2 and 6.2 eV were used in the air/sample optical model to get knowledge about complex pseudodielectric constant, pseudorefractive index, pseudoextinction and absorption coefficients of the crystals. Spectral change of real and imaginary part of complex pseudodielectric constant were discussed in detail. Band gap energy of Bi12GeO20 single crystals was calculated to be 3.18 eV using absorption coefficient dependency on photon energy. Critical point energies at which photons are strongly absorbed were determined by utilizing the second energy derivative spectra of components of complex pseudodielectric function. Fitting of both spectra resulted in the presence of four interband transitions with energies of 3.49, 4.11, 4.67 and 5.51 eV.

Isik, M., Delice, S., Gasanly, N. M., Darvishov, N. H., & Bagiev, V. E. (2020). Investigation of optical properties of Bi12GeO20 sillenite crystals by spectroscopic ellipsometry and raman spectroscopy. Ceramics International, 46(9), 12905-12910. doi:10.1016/j.ceramint.2020.02.056


Article access:

METU Author

Prof. Nizami Hasanlı Scopus Author ID: 35580905900
About the author


Sillenites, Ellipsometry, Raman, Optical properties

Other authors:
Isik, M., Delice, S., Darvishov, N. H., & Bagiev, V. E.

This work was supported by Atilim University under Grant No: ATÜ-ADP-1920-03.