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Theoretical analysis of nucleation and growth of ZnO nanostructures in vapour phase transport growth

Saunders, Ruth B., McGlynn, Enda orcid logoORCID: 0000-0002-3412-9035 and Henry, Martin O. (2011) Theoretical analysis of nucleation and growth of ZnO nanostructures in vapour phase transport growth. Crystal Growth & Design, 11 (10). pp. 4581-4587. ISSN 1528-7505

Abstract
This paper discusses the growth atmosphere, condensing species and nucleation conditions relevant to vapour phase transport growth of ZnO nanostructures, including the molecular parameters and thermodynamics of the gas phase ZnO molecule and its importance compared to atomic Zn and molecular O2. The partial pressure of molecular ZnO in a Zn/O2 mix at normal ZnO growth temperatures is 6x10^-7 of the Zn partial pressures. In typical vapour phase transport growth conditions, using carbothermal reduction, the Zn vapour is always undersaturated while the ZnO vapour is always supersaturated. In the case of the ZnO vapour, our analysis suggests that the barrier to homogeneous nucleation (or heterogeneous nucleation at unseeded/uncatalysed areas of the substrates) is too large for nucleation of this species to take place, which is consistent with experimental evidence that nanostructures will not grow on unseeded areas of substrates. In the presence of suitable accommodation sites, due to ZnO seeds, growth can occur via Zn vapour condensation (followed by oxidation) and via direct condensation of molecular ZnO (whose flux at the surface, although less than that of Zn vapour, is still sufficient to yield an appreciable nanostructure deposit). The balance between these two condensing species is likely to be a sensitive function of growth parameters and could explain both the diversity of reported nanostructure morphologies and the challenges to be faced in developing reproducible and scalable growth systems for specific applicable morphologies.
Metadata
Item Type:Article (Published)
Refereed:Yes
Subjects:Engineering > Materials
Physical Sciences > Nanotechnology
Physical Sciences > Chemistry
Physical Sciences > Semiconductors
DCU Faculties and Centres:Research Initiatives and Centres > National Centre for Plasma Science and Technology (NCPST)
DCU Faculties and Schools > Faculty of Science and Health > School of Physical Sciences
Publisher:American Chemical Society
Official URL:http://dx.doi.org/10.1021/cg200828y
Copyright Information:© 2011 ACS This document is the Accepted Manuscript version of a Published Work that appeared in final form in Crystal Growth & Design, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/cg200828y
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 3.0 License. View License
ID Code:19659
Deposited On:19 Nov 2013 15:18 by Enda Mcglynn . Last Modified 19 Mar 2019 15:34
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