Date of Award

2007

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Physics

Advisor

Robert J. Lad

Second Committee Member

Brian G. Frederick

Third Committee Member

George P. Bernhardt

Abstract

This project has demonstrated how controlled synthesis of nanostructured SiAION thin films with varying composition produces an outstanding class of wear resistant and oxidation resistant coatings. SiAION thin films spanning the full range of Oxygen/Nitrogen and Aluminum/Silicon ratios were deposited by Radio Frequency magnetron co-sputtering of aluminum (Al) and silicon (Si) sputter targets in argon/oxygen/nitrogen mixtures onto both bare sapphire and Pt coated sapphire substrates. The films are amorphous and very smooth when deposited at 200°C and remain amorphous even after extended post-deposition annealing in vacuum, molecular nitrogen (N2), or air up to 1500°C. Nitrogen rich film compositions are extremely wear resistant when measured in sliding contact with steel or sapphire pins. The film stoichiometry remains unchanged at high temperature in vacuum or N2 but the films lose nitrogen during air annealing. A thin film interfacial oxidation sensor was developed and embedded at the SiAION / substrate interface, and the oxygen penetration rate through the SiAION film structures was inferred during isothermal annealing experiments at 1000°C in air. Film exposure to oxygen radicals O* and 02+ species produced by an electron cyclotron resonance (ECR) source was carried out and shown to lead to rapid surface oxidation and nitrogen loss. Gradient film compositions offer the possibility of improved oxidation resistance.

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