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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Electrical Engineering and Computer Science

First Advisor

Qi Hua Fan


Low refractive index materials are vital for antireflection coatings. Porous anodic aluminum oxide on glass has potential to be a suitable antireflection coating as its refractive index can be adjusted between 1.1 and 1.5 with good mechanical strength. However, it is unclear how anodic aluminum oxide porosity can be controlled to achieve an optimal refractive index. Also, the optical film thickness, composition, optical properties and role of residual aluminum in thin film anodic aluminum oxide are unknown. The objective of this thesis was to fabricate porous anodic aluminum oxide thin films on glass with a refractive index around 1.25, and reflectance less than 6%, and also to identify films that can be used with the anodic aluminum oxide films, such as silicon and gold. The refractive index of porous materials is a combination of the refractive indices of air and the solid. In this study, porous anodic aluminum oxide was fabricated on glass substrate by electrochemical anodization and subsequent wet chemical etching. Films anodized at room temperature and successive wet chemical etching had refractive indices less than 1.25 in the visible and infra-red regions, and reflectance less than 5% in the entire wavelength range. When used with silicon, the thin film anodic aluminum oxide provided three times higher absorption. A thick layer of gold on the anodic aluminum oxide resulted in high reflectance from the gold in the IR region. This isthe first report of anodic aluminum oxide on glass with a refractive index less than 1.25 in the visible and infra-red regions, and silicon and gold as antireflection layer for thin films. Future work should include determining the optimal pore shapes to achieve minimum reflectance.

Library of Congress Subject Headings

Aluminum oxide
Anti-reflective coatings
Thin films
Solar energy


Includes bibliographical references (pages 74-81)



Number of Pages



South Dakota State University


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