Reflectivity of Silver and Gold as a Function of Temperature at Four Micron Wavelength.

摘要

Reflectivity measurements were made on evaporated films of thicknesses ranging from those that were barely continuous to ones thick enough to be opaque. Each measurement included one sample with a surface which would be smooth to the metal's free electrons and one which would be rough. The temperature ranged from 2 to 400 Kelvin. Resistivity and Hall Coefficient were also measured so that the free-carrier density and mean-free-path of the conduction electrons could be determined. The results are surprising since they do not show the nearly linear relation between reflectivity and resistivity, or between reflectivity and temperature, that is predicted by theory. Instead reflectivity first rises to a peak at about 200 K and then drops as the temperature is changed from 400 to 2 K. All twelve samples measured show the same general change in reflectivity with temperature although the exact amount is not consistent. The average is 2% lower at 4 than it was at 200 K. This difference is about an order of magnitude greater than the uncertainty of the measurements. The difference in reflectivity between rough and smooth samples remains constant throughout the temperature range. (Author)