Structural and temperature-tuned optical characteristics of Bi12GeO20 sillenite crystals

Üniversitemiz öğretim üyelerinden Prof. Dr. Nızamı Hasanlı’nın yazarları arasında bulunduğu “Structural and temperature-tuned optical characteristics of Bi₁₂GeO₂₀ sillenite crystals” başlıklı makale Chinese Journal of Physics’de yayınlandı.

Sillenite compounds exhibit unique photorefractive and electro-optic characteristics providing attractiveness to these materials in various optoelectronic applications. The present paper aims at investigating one of the members of this family. Structural and optical characteristics of Bi₁₂GeO₂₀ (BGO) were studied by means of x-ray diffraction, Raman spectroscopy and temperature-dependent transmittance measurements. Obtained transmission curves in the wavelength range of 350−1100 nm and at different applied temperatures between 10 and 300 K were employed to find out the absorption coefficient dependence on the photon energy. Tauc relation revealed the presence of an energy gap of 2.49 eV at room temperature. Extension of energy gap up to 2.57 eV due to decreased temperature down to 10 K was deduced by the analysis. In order to have reliable results, the energy gap value was corroborated by utilizing derivative spectral method and well consistency between both methods was indicated. Energy gap change with temperature was also discussed in the study using an empirical formula developed by Varshni. Energy gap at absolute zero and rate of band gap alteration with temperature were determined as 2.57 eV and −2.4 × 10⁻⁴ eV K ^{− 1}, respectively. Taking into account the previously reported studies on investigation of band gap characteristics of BGO, intrinsic Bi_Ge³⁺+V_O⁺ defect could be responsible for the revealed energy value of 2.49 eV which is much lower than reported band gap energy of ~3.2 eV.

Delice, S., Isik, M., Gasanly, N. M., Darvishov, N. H., & Bagiev, V. E. (2020). Structural and temperature-tuned optical characteristics of Bi12GeO20 sillenite crystals. Chinese Journal of Physics, 66, 422-429. doi:10.1016/j.cjph.2020.04.005

Makaleye erişim için: https://www.sciencedirect.com/science/article/abs/pii/S0577907320300939?via%3Dihub

Anahtar sözcükler:

Bismuth germanium oxide; Optical properties; Sillenites

Diğer Yazarlar:

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

Ek Bilgiler:

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