Ellipsometric Study of Oxide Films Formed on LDEF Metal Samples
Abstract
The optical constants of samples of six different metals (Al, Cu, Ni, Ta, W, and Zr) exposed to space on the long duration exposure facility (LDEF) have been studied by variable angle spectroscopic ellipsometry. Measurements were also carried out on portions of each sample which were shielded from direct exposure by a metal bar. A least-squares fit of the data using an effective medium approximation was then carried out with thickness and composition of surface films formed on the metal substrates as variable parameters. The analysis revealed that exposed portions of the Cu, Ni, Ta, and Zr samples are covered with porous oxide films ranging in thickness from 500 Angstrom A to 1000 Angstrom A. The 410 Angstrom A thick film of A1203 on the exposed Al sample is practically free of voids. Except for Cu, the shielded portions of these metals are covered by thin nonporous oxide films characteristic of exposure to air. The shielded part of the Cu sample has a much thicker porous coating of Cu2O. The tungsten data could not be analyzed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1992
- Accession Number
- ADA249856
Entities
People
- Judith S. Brodkin
- Louise C. Sengupta
- Paul L. Sagalyn
- Wolfgang Franzen