Electronic structure and optical responses of nanocrystalline BiGaO3 films: A combination study of experiment and theory

Abstract

Growth and optical properties of SrBi 2 Nb 2 O 9 ferroelectric thin films using pulsed laser deposition High-quality nanocrystalline BiGaO 3 (BGO) films have been prepared by a modified sol-gel method. X-ray diffraction analysis shows that the films are polycrystalline and exhibit an orthorhombic structure. The dispersion functions near infrared-ultraviolet region were extracted by fitting spectroscopic ellipsometry with the Tauc-Lorentz model. Moreover, first-principle calculations on dielectric functions and band gap were carried out, which are in good agreement with the experimental results. It was found that BGO belongs to an indirect band gap oxide with the fundamental gap of about 2.17 eV, which is suitable for ferroelectric based photovoltaic devices. V C 2014 AIP Publishing LLC. [http://dx.

Comparative density functional studies of BiMO3 polymorphs (M = Al, Ga, In) based on LDA, GGA, and meta-GGA functionals

“…Unfortunately, there are not many experimental reports of the band gap values for the considered compounds. In particular, there are no experimental values of E g for BiAlO 3 , whereas, for BiGaO 3 and BiInO 3 , the measured values of E g are 2.17 eV 59 and 4.5 eV, 60 respectively. In the case of BiInO 3 , the E g value was obtained for the Pnma structure and not for Pna 2 1 .…”

“…We started our consideration by the comparison of the results obtained using different exchange–correlation functionals for the ambient pressure phases of BiAlO 3 , BiGaO 3 , and BiInO 3 with the available experimental data from ref. 21, 22 and 59–61. The results presented in this section were obtained using the LDA, GGAs (PBE, PBEsol, and AM05), meta -GGAs (MS0, MS1, MS2, and SCAN), and the hybrid HSE functional.…”

“…The structural and electronic properties of these compounds were reported previously by other authors. 23,25,54,59,70–81 Most of their results were obtained using the LDA or GGA. Here, we repeated them to compare with the results obtained using the AM05 and meta -GGA functionals, which have not been used to study the properties of the aforementioned compounds.…”

“…As a starting point for the structure optimization of BiMO 3 polymorphs (M = Al, Ga, In) we took the experimental parameters from ref. 13–15, 21, 22, 26, 59–67. The Brillouin-zone integrations were performed using 16 × 16 × 16, 12 × 12 × 12, 8 × 8 × 8, and 6 × 6 × 6 Γ -centered k -point grids for 5-, 10-, 20-, and 40-atom unit cells, respectively.…”