Published: Jan 1988
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The absorptance of gold films deposited under a variety of conditions was measured to an accuracy of.0002 with an HF Laser Calorimeter. The absorptance was observed to vary from.0107 to.0091, which is an 18% change.
The specimens were analyzed with a Perkin-Elmer PHI Auger spectrometer and the absorptance was found to be directly correlated with the impurity content.
The impurities were determined to originate in the residual gas in the chamber. A Dycor residual gas analyzer was used to locate and eliminate the sources of the impurities.
Films deposited at the same rates and temperatures, but with essentially no impurities were found to have absorptance ten times greater than the original films. These films have a dramatically different structure. They have been commonly observed, and are generally described as “recrystallized.”
Impurities were intentionally added to produce an absorptance of approximately.0095. The doped films were observed to be substantially more stable than un-doped films under thermal cycling between room temperature and 225°C. The dopant atoms are believed to pin the grain boundaries. While no quantitative hardness measurements were made. The doped films are also expected to be harder.
Similar results were observed for silver. Partial recrystallization is hypothosized to explain the reflectance degradation of siver based EHR coatings reported by Dr. Don Decker in 1982.
contaminant related absorptance, gold films, recrystallization, silver films, thermal cycling