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Comparative study of the structural and optical properties of epitaxial CuFeO2 and CuFe1 - xGaxO2 delafossite thin films grown by pulsed laser deposition methods

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journal contribution
posted on 19.07.2017, 10:13 authored by R.A. Wheatley, S. Rojas, C. Oppolzer, Toyanath Joshi, Pavel BorisovPavel Borisov, David Lederman, A.L. Cabrera
Three samples of epitaxial delafossite CuFeO2 and CuFe1 − xGaxO2 films were grown using Pulsed Laser Deposition techniques in high vacuum. The sample thicknesses were estimated to be 21 nm, 75 nm for the CuFeO2 films and ~ 37 nm for the composite sample containing gallium. The estimated gallium fraction of substituted ferric atoms was x = 0.25 for the composite sample. We present the study of the fundamental band gap(s) for each sample via observation of their respective optical absorption properties in the NIR-VIS region using transmittance and diffuse reflection spectroscopy. Predominant absorption edges measured at 1.1 eV and 2.1 eV from transmittance spectra were observed for the CuFeO2 samples. The sample of CuFe1 − xGaxO2 showed a measurable shift to 1.5 eV of the lower band-gap and a strong absorption edge located at 2.3 eV attributed to direct band to band transitions. This study also found evidence of changes between apparent absorption edges between transmittance and diffuse reflectance spectroscopies of each sample and it may be resultant from absorption channels via surface states.

Funding

This work at PUC was supported by FONDECyT 1130372 and Proyecto Anillo ACT1409. This work at WVU was supported in part by the WV Higher Education Policy Commission (grant HEPC.dsr.12.29) and by FAME, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA (contract # 2013-MA-2382).

History

School

  • Science

Department

  • Physics

Published in

Thin Solid Films

Volume

626

Pages

110 - 116

Citation

WHEATLEY, R.A. ... et al, 2017. Comparative study of the structural and optical properties of epitaxial CuFeO2 and CuFe1 − xGaxO2 delafossite thin films grown by pulsed laser deposition methods. Thin Solid Films, 626, pp. 110-116.

Publisher

© Elsevier

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Acceptance date

03/02/2017

Publication date

2017

Notes

This paper was accepted for publication in the journal Thin Solid Films and the definitive published version is available at http://dx.doi.org/10.1016/j.tsf.2017.02.005

ISSN

0040-6090

Language

en