Growth of epitaxial ZnO films on sapphire substrates by plasma assisted molecular beam epitaxy

Adam R. Hyndman; Martin W. Allen; Roger J. Reeves

doi:10.1117/12.2179709

Abstract

Epitaxial layers of ZnO have been grown on c-plane, (0001) sapphire substrates by plasma assisted molecular beam epitaxy. The oxygen:zinc flux ratio was found to be crucial in obtaining a film with a smooth surface and good crystallinity. When increasing film thickness from ~80 to 220 nm we observed an increase in the streakiness of RHEED images, and XRD revealed a reduction in crystal strain and increase in crystal alignment. A film with surface roughness of 0.5 nm and a XRD rocking curve FWHM of 0.1 for the main ZnO peak (0002) was achieved by depositing a low temperature ZnO buffer layer at 450 °C and then growing for 120 minutes at 700 °C with a Zn-cell temperature of 320 °C and an oxygen partial pressure of 7e^-7 Torr. We found novel structures on two samples grown outside of our ideal oxygen:zinc flux ratio. SEM images of a sample believed to have been grown in a Zn-rich environment showed flower like structures up to 150 um in diameter which appear to have formed during growth. Another sample believed to have been deposited in a Zn-deficient environment had rings approximately 1.5 um in diameter scattered on its surface.

Citation Download Citation

Adam R. Hyndman, Adam R. Hyndman, Martin W. Allen, Martin W. Allen, Roger J. Reeves, Roger J. Reeves, } "Growth of epitaxial ZnO films on sapphire substrates by plasma assisted molecular beam epitaxy", Proc. SPIE 9364, Oxide-based Materials and Devices VI, 93640X (13 March 2015); doi: 10.1117/12.2179709; https://doi.org/10.1117/12.2179709

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