Chemical-etch-assisted growth of epitaxial zinc oxide

TL;DR

This paper presents a real-time spectroscopic polarimetric method for growing dense, two-dimensional zinc oxide epitaxially on sapphire, utilizing chemical modeling and gas-phase zinc oxide particulates to optimize deposition and etching cycles.

Contribution

It introduces a novel real-time monitoring technique combined with chemical modeling to control zinc oxide epitaxial growth on sapphire, highlighting the importance of seed layers and process cycling.

Findings

A seed layer is essential for growth.

Unwanted ZnO deposits can be removed by cycling between deposition and etching.

Transition between processes occurs with minimal precursor concentration change.

Abstract

We use real-time spectroscopic polarimetric observations of growth and a chemical model derived therefrom, to develop a method of growing dense, two-dimensional zinc oxide epitaxially on sapphire by metalorganic chemical vapor deposition. Particulate zinc oxide formed in the gas phase is used to advantage as the deposition source. Our real-time data provide unequivocal evidence that: a seed layer is required; unwanted fractions of ZnO are deposited; but these fractions can be removed by cycling between brief periods of net deposition and etching. The transition between deposition and etching occurs with zinc precursor concentrations that only differ by 13%. These processes are understood by considering the chemistry involved.