Issue 24, 2017

The dominant effect of non-centrosymmetric displacement on the crystal-field energy splitting in the strained a-plane ZnO epi-films on r-plane sapphires

Abstract

The polarization-dependent photoluminescence (PL) of the a-plane ZnO (a-ZnO) films grown on r-plane sapphire substrates shows that the crystal-field energy splitting (ΔCF) becomes larger with increasing film thickness from 24 nm to 291 nm. In the use of the nonlinear fitting of the stress–strain tensor to the X-ray diffraction data, we found crystal symmetry breaking from wurtzite to monoclinic in these films and determined the corresponding lattice constants and the relaxed lattice constants. With the available lattice variables, we further used the tight-binding method to calculate the band energies and compared with the PL spectra. The results confirm that the crystal deformation and the non-centrosymmetric displacement had opposite effects on the ΔCF at the Γ point and the displacement induced by the strain is the dominant effect on ΔCF.

Graphical abstract: The dominant effect of non-centrosymmetric displacement on the crystal-field energy splitting in the strained a-plane ZnO epi-films on r-plane sapphires

Article information

Article type
Paper
Submitted
14 Mar 2017
Accepted
19 May 2017
First published
19 May 2017

CrystEngComm, 2017,19, 3348-3354

The dominant effect of non-centrosymmetric displacement on the crystal-field energy splitting in the strained a-plane ZnO epi-films on r-plane sapphires

Y. Wu, W. Liu, H. Chen, C. Hsu and W. Hsieh, CrystEngComm, 2017, 19, 3348 DOI: 10.1039/C7CE00500H

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