Date of Award

1996

Degree Name

M.S. in Materials Engineering

Department

Department of Chemical and Materials Engineering

Abstract

NbN films have been investigated to determine the effects of microstructure and chemistry on wear and friction coefficients in dry and humid environments. Using magnetron sputtering, NbN films of different stoichiometries and crystal structures have been deposited on 440C substrates by varying the partial pressure of nitrogen (Pn2) and substrate bias potential. In this study, cubic, mixed cubic/hexagonal, and hexagonal films were investigated. The chemistry and structure of the NbN films were evaluated with X-ray Photoelectron Spectroscopy (XPS) and X-ray Diffraction (XRD). All of the films were then studied to determine their relative tribological properties in dry (2-5% RH) and humid (80-85% RH) environments using a ball-on-flat tribometer enclosed in an environmental chamber. Silicon nitride balls (1/4” in diameter) are used as the counterface material. The crystal structure and chemistry of the films have only a minor effect on the friction coefficiant and wear rate. Moisture content in the test environment, however, has a significant effect on tribological properties. For example, with cubic samples, ball wear increases from 0.3x10‘3 mm3 to 2.0x1 O'3 mm3 upon increasing the humidity from 2% to 80%. The friction coefficient (|i) of cubic films tested in the humid condition is lower (p. =0.5) relative to those tested in dry conditions (p =0.8). This phenomena is marked by a change in wear mechanism as is evidenced by dissimilar wear debris for each of the environments. Powdery debris is formed in the humid environment and rolled particles are formed in dry environments. The effect of debris on friction and wear is discussed.

Keywords

Niobium nitride, Semiconductor films, Thin films, Tribology, Mechanical wear

Rights Statement

Copyright © 1996, author

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