Issue 1, 2022

Pulsed heating atomic layer deposition (PH-ALD) for epitaxial growth of zinc oxide thin films on c-plane sapphire

Abstract

An in situ pulsed heating atomic layer deposition (PH-ALD) technique is used to grow heteroepitaxial ZnO thin films on c-plane sapphire with temperature-sensitive metalorganic precursors. During metalorganic precursor delivery, the substrate is maintained at a base temperature of 110 °C to prevent thermal decomposition of the precursors. After the substrate is sequentially exposed to the metalorganic precursor and water co-reactant at this low temperature, a high-power resistive heater is used to rapidly heat the substrate to between 400 and 900 °C to drive film crystallization. These in situ heat pulses enable epitaxial growth of (0001) ZnO films on c-plane sapphire. Rocking curves with FWHM of values as low as 0.53° are achieved. In contrast, films deposited entirely at 110 °C appear random polycrystalline and post-deposition annealing to 900 °C achieves only partial “epitaxial character” with a notably different in-plane orientation. Variations in heat pulse temperature and the number of deposition cycles between heat pulses are explored. Epitaxial growth persists up to 5 deposition cycles per heat pulse, with the 2θω FWHM increasing to 1–2°. To further reduce process times, a templating approach is also explored in which a limited number of “template” layers are initially deposited with PH-ALD followed by low-temperature ALD at 110 °C. Epitaxial growth is encouraged with as few as 5 cycles of PH-ALD followed by 495 cycles of low-temperature ALD. Crystal quality further improves by using up to 50 template cycles, with a 2θω FWHM of 1.3°. Epilayers also show enhanced photoluminescence (PL) at room temperature. These results demonstrate how in situ pulse-heating can be used to promote epitaxial film growth in ALD processes using temperature-sensitive metalorganic precursors.

Graphical abstract: Pulsed heating atomic layer deposition (PH-ALD) for epitaxial growth of zinc oxide thin films on c-plane sapphire

Supplementary files

Article information

Article type
Paper
Submitted
22 אוק 2021
Accepted
06 דצמ 2021
First published
06 דצמ 2021

Dalton Trans., 2022,51, 303-311

Author version available

Pulsed heating atomic layer deposition (PH-ALD) for epitaxial growth of zinc oxide thin films on c-plane sapphire

B. D. Piercy, J. P. Wooding, S. A. Gregory and M. D. Losego, Dalton Trans., 2022, 51, 303 DOI: 10.1039/D1DT03581A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements