Publication

Optical properties of anodically degraded ZnO

Christophe Ballif, Sylvain Nicolay
2014
Journal Articles

Abstract

We discuss the optical properties of non-degraded and anodically degraded boron-doped zinc oxide (ZnO:B) deposited by low-pressure chemical vapour deposition on soda-lime glass. The optical model used to simulate the infrared reflectance in the wavelength range between 1.2 and 25 mu m is based on the Maxwell-Garnett effective-medium theory. The model is sensitive to the conditions at the grain boundaries of the investigated polycrystalline ZnO: B films. We confirm that the presence of defect-rich grain boundaries, especially after degradation, causes a highly resistive ZnO: B film. Furthermore, indications of a degraded zinc oxide layer next to the ZnO:B/glass interface with different refractive index are found. We present evidence for the creation of oxygen vacancies, based on Raman investigations, which correlate with a shift of the optical absorption edge of the ZnO: B. Investigations with scanning and transmission electron microscopy show microvoids at the grain boundaries after anodic degradation. This indicates that the grain/grain interfaces are the principle location of defects after degradation. (C) 2014 AIP Publishing LLC.

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https://infoscience.epfl.ch/entities/publication/39852549-fb83-4a78-b7b3-7d62839a19a0

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Christophe Ballif, Sylvain Nicolay
2014
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/39852549-fb83-4a78-b7b3-7d62839a19a0

About this result

Related concepts (32)

Grain boundary

In materials science, a grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are two-dimensional defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material. Most grain boundaries are preferred sites for the onset of corrosion and for the precipitation of new phases from the solid. They are also important to many of the mechanisms of creep.

Abnormal grain growth

Abnormal or discontinuous grain growth, also referred to as exaggerated or secondary recrystallisation grain growth, is a grain growth phenomenon through which certain energetically favorable grains (crystallites) grow rapidly in a matrix of finer grains resulting in a bimodal grain size distribution. In ceramic materials this phenomenon can result in the formation of elongated prismatic, acicular (needle-like) grains in a densified matrix with implications for improved fracture toughness through the impedance of crack propagation.

Crystallite

A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains. Bacillite is a type of crystallite. It is rodlike with parallel longulites. The orientation of crystallites can be random with no preferred direction, called random texture, or directed, possibly due to growth and processing conditions.

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