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Surface- and strain-tuning of the optical dielectric function in epitaxially grown CaMnO3
Journal article   Open access   Peer reviewed

Surface- and strain-tuning of the optical dielectric function in epitaxially grown CaMnO3

Dominic Imbrenda, Dongyue Yang, Hongwei Wang, Andrew R. Akbashev, Leila Kasaei, Bruce A. Davidson, Xifan Wu, Xiaoxing Xi and Jonathan E. Spanier
Applied physics letters, v 108(8)
22 Feb 2016
DOI: https://doi.org/10.1063/1.4942374
url
http://arxiv.org/abs/1510.01709View
SubmittedOpen Access (License Unspecified),  Open

Abstract

Physical Sciences Physics Physics, Applied Science & Technology
We report a strong thickness dependence of the complex frequency-dependent optical dielectric function (epsilon) over tilde(omega) over a spectral range from 1.24 to 5 eV in epitaxial CaMnO3(001) thin films on SrTiO3(001), LaAlO3(001), and SrLaAlO4(001). A doubling of the peak value of the imaginary part of (epsilon) over tilde(omega) and spectral shifts of 0.5 eV for a given magnitude of absorption are observed. On the basis of experimental analyses and first-principles density functional theory calculations, contributions from both surface states and epitaxial strain to the optical dielectric function of CaMnO3 are seen. Its evolution with thickness from 4 to 63 nm has several regimes. In the thinnest, strain-coherent films, the response is characterized by a significant contribution from the free surface that dominates strain effects. However, at intermediate and larger thicknesses approaching the bulk-like film, strain coherence and partial strain relaxation coexist and influence (epsilon) over tilde(omega). (C) 2016 AIP Publishing LLC.

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Domestic collaboration
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Physics, Applied
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