Abstract
The optical properties of several commonly used single-crystal oxide substrates were explored by spectroscopic ellipsometry over a wide spectral range from 0.74 eV to 8.8 eV. The crystals examined are (100) SrTiO3, 0.7 % wt Nb-doped (100) SrTiO3,(100) (LaAlO3)0.29(SrAl0.5Ta0.5O3)0.7, (011) DyScO3, (100) MgAl2O4, (100) MgO, and (100) LaAlO3, all of which enable epitaxial growth of numerous perovskite-type and other optical thin films. An analytic form for the complex dielectric function was derived from ellipsometric data through a physically consistent modeling process. The obtained dielectric spectra were further utilized to calculate the complex index of refraction and absorption coefficient for each substrate material. The absorption spectra and optical band gap were analyzed using Tauc plots. The parameters for reconstructing the dielectric functions are given in detail, allowing for extensive applications of the results of this work.
Highlights
Many ABX3 materials possessing perovskite-type structure exhibit functional responses that are intriguing fundamentally and useful for practical applications
Advancements in non-destructive characterization techniques such as Raman spectroscopy, reflectometry, and ellipsometry have made it possible to determine the optical functions of these materials, either as bulk crystals or as thin films, accurately in a broad spectral range [20]
It is worth noting that lattice strain induced by a mismatch between crystal lattices of substrates and thin films is a powerful tool to manipulate many of the thin-film properties [21,22,23,24,25]
Summary
Many ABX3 materials possessing perovskite-type structure exhibit functional responses that are intriguing fundamentally and useful for practical applications. We have applied variable angle spectroscopic ellipsometry (VASE) in the IR-VIS -VUV spectral range with photon energies ranging from 0.78 to 8.8 eV in order to accurately determine a functional form of the complex dielectric function and, the complex refractive indices and absorption coefficients of all aforementioned crystal substrates We further use this data to determine the type and energy level of the optical bandgap for each of these substrates, and this data is tabulated and compared to previous work for easy reference. The results of our studies are summarized as a comprehensive and practical resource to precisely reconstruct the complex dielectric function in a broad optical range, providing a useful link to all optical constants for the substrates
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