header

Quantifying Competitive Grain Overgrowth in Polycrystalline ZnO Thin Films

47 Pages Posted: 28 Mar 2019 First Look: Accepted

See all articles by A. Brian Aebersold

A. Brian Aebersold

Ecole Polytechnique Fédérale de Lausanne - Interdisciplinary Centre for Electron Microscopy (CIME)

Lorenzo Fanni

Ecole Polytechnique Fédérale de Lausanne - Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab)

Aïcha Hessler-Wyser

Ecole Polytechnique Fédérale de Lausanne - Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab)

Sylvain Nicolay

PV-Center - CSEM

Christophe Ballif

Ecole Polytechnique Fédérale de Lausanne - Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab)

Cécile Hébert

Ecole Polytechnique Fédérale de Lausanne - Interdisciplinary Centre for Electron Microscopy (CIME); Ecole Polytechnique Fédérale de Lausanne - Electron Spectrometry and Microscopy Laboratory (LSME)

Duncan T.L. Alexander

Ecole Polytechnique Fédérale de Lausanne - Interdisciplinary Centre for Electron Microscopy (CIME)

Abstract

The grain size evolution of polycrystalline thin films, which form by competitive grain overgrowth as commonly interpreted using the van der Drift model, is understood to follow a power-law scaling of the average grain size d with film thickness h, i.e. dhα. While simulations have identified a growth exponent α = 0.4 for three-dimensional growth, previous experimental studies did not confirm this value, instead finding α values in the range of ~0.5-0.7. Here we study competitive grain overgrowth using a system of ZnO thin films grown by low-pressure metal-organic chemical vapor deposition. We present quantitative grain data on the evolution of grain size and orientation across the thickness of thin films, obtained by automated crystal orientation mapping of "double-wedge" transmission electron microscopy samples. The data from a-textured ZnO films, grown under three different conditions, are compared against van der Drift model predictions of self-similarity of the grain size distribution and the power-law scaling. The results are further interpreted by comparing to simulations of facetted polycrystalline film growth, which we adapt to the ZnO system by including idiomorphic growth shapes with a six-fold symmetry and random or biased nuclei orientations. As well as showing the predicted self-similarity of grain size distributions during growth, for the first time our experimental data confirm a power-law growth exponent of α = 0.4, as also predicted by the simulations using randomly oriented nuclei. Nevertheless, interpretation of this result is contingent on the absence of factors such as textured nucleation and renucleation during film growth. Indeed, only one film, grown at a higher ratio of H2O/DEZ precursor gases, displaying random initial nucleation, and minimal grain renucleation during growth, shows a proper conformance to the model nature and predictions.

Keywords: Competitive Grain Growth, Transmission Electron Microscopy (TEM), Automated Crystal Orientation Mapping (ACOM), LP-MOCVD ZnO, Film Growth

Suggested Citation

Aebersold, A. Brian and Fanni, Lorenzo and Hessler-Wyser, Aïcha and Nicolay, Sylvain and Ballif, Christophe and Hébert, Cécile and Alexander, Duncan T.L., Quantifying Competitive Grain Overgrowth in Polycrystalline ZnO Thin Films (March 23, 2019). Available at SSRN: https://ssrn.com/abstract=3358865

A. Brian Aebersold (Contact Author)

Ecole Polytechnique Fédérale de Lausanne - Interdisciplinary Centre for Electron Microscopy (CIME)

Station 5
Odyssea 1.04
1015 Lausanne, CH-1015
Switzerland

Lorenzo Fanni

Ecole Polytechnique Fédérale de Lausanne - Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab)

Station 5
Odyssea 1.04
1015 Lausanne, CH-1015
Switzerland

Aïcha Hessler-Wyser

Ecole Polytechnique Fédérale de Lausanne - Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab)

Station 5
Odyssea 1.04
1015 Lausanne, CH-1015
Switzerland

Sylvain Nicolay

PV-Center - CSEM

Neuchâtel
Switzerland

Christophe Ballif

Ecole Polytechnique Fédérale de Lausanne - Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab)

Station 5
Odyssea 1.04
1015 Lausanne, CH-1015
Switzerland

Cécile Hébert

Ecole Polytechnique Fédérale de Lausanne - Interdisciplinary Centre for Electron Microscopy (CIME)

Station 5
Odyssea 1.04
1015 Lausanne, CH-1015
Switzerland

Ecole Polytechnique Fédérale de Lausanne - Electron Spectrometry and Microscopy Laboratory (LSME)

Station 5
Odyssea 1.04
1015 Lausanne, CH-1015
Switzerland

Duncan T.L. Alexander

Ecole Polytechnique Fédérale de Lausanne - Interdisciplinary Centre for Electron Microscopy (CIME) ( email )

Station 5
Odyssea 1.04
1015 Lausanne, CH-1015
Switzerland

Here is the Coronavirus
related research on SSRN

Paper statistics

Abstract Views
68
Downloads
4