Derivative optical spectroscopy of thin films of alkaline-earth titanates: Critical points

Jarmila Müllerová,Pavel Šutta,Lucie Prušáková

doi:10.1063/1.5048882

Abstract

This paper analyzes UV Vis absorption spectra of amorphous thin films of barium strontium titanate (BST) deposited by RF magnetron sputtering on SiO2 at different substrate temperatures. The Tauc procedure was used to determine optical band gaps for direct and indirect interband transitions. This procedure was accompanied by derivative spectroscopy useful in case of multicomponent systems. Higher-order derivatives were used to find the so-called critical points related to the optical interband transitions at various regions in the Brillouin zone. Three critical points were identified in BST thin films spectra of dielectric function. All optical band gaps and energies of critical points were found to decrease with the substrate temperature at the deposition.

Highlights

Alkaline earth titanates such as BaTiO3 (BTO), SrTiO3 (STO) are perovskite-type compounds with excellent properties suitable for electronic and optoelectronic devices, e.g. as sensors, actuators, optical modulators, optical windows and memories, optical filters etc. [1], [2]
Three critical points were identified in barium strontium titanate (BST) thin films spectra of dielectric function
All optical band gaps and energies of critical points were found to decrease with the substrate temperature at the deposition

Summary

Introduction

Alkaline earth titanates such as BaTiO3 (BTO), SrTiO3 (STO) are perovskite-type compounds with excellent properties suitable for electronic and optoelectronic devices, e.g. as sensors, actuators, optical modulators, optical windows and memories, optical filters etc. [1], [2]. This paper analyzes UV Vis absorption spectra of amorphous thin films of barium strontium titanate (BST) deposited by RF magnetron sputtering on SiO2 at different substrate temperatures. The Tauc procedure was used to determine optical band gaps for direct and indirect interband transitions. Higher-order derivatives were used to find the so-called critical points related to the optical interband transitions at various regions in the Brillouin zone.

Results

Conclusion