J. Phys. Colloques
Volume 42, Numéro C1, Janvier 1981Conférence Internationale sur les Matériaux pour la Conversion Photothermique de l'Energie Solaire
|Page(s)||C1-203 - C1-211|
J. Phys. Colloques 42 (1981) C1-203-C1-211
CVD MOLYBDENUM FILMS OF HIGH INFRARED REFLECTANCE AND SIGNIFICANT SOLAR ABSORPTANCEG.E. Carver1 et E.E. Chain2
1 Visiting Scientist at U.S.T.L., Laboratoire de Spectroscopie II, F-34060, Montpellier, France, May-October 1980, funded by CNRS-NSF Exchange of Scientists Program.
2 Optical Sciences Center, University of Arizona, Tucson, Arizona 85721, U.S.A.
Chemical Vapor Deposition (CVD) of thin films from molybdenum carbonyl (Mo (CO) 6) at 300 °C under atmospheric pressure has resulted in either reflective or black molybdenum, depending on the absence or presence of an oxygen bleed during the deposition. After post-deposition anneal, the reflective film exhibits an infrared reflectance of 98.7 % at 10 microns while the black film exhibits a solar absorptance of a = 0.74 and a thermal (500°C) emittance of en = 0.08, (en referring to the normal emittance). The reflectance of both films, before and after anneal, has been related to their composition, grain size, and crystal structure. In particular this has been done in the infrared for the reflective films and in the visible for the black films. The solar absorptance of both film types can be enhanced by one or two antireflection layers with only slight increases in the emittance. A bilayer of CVD silicon (700 Å) and silicon nitride (700 Å) on the annealed reflective film results in a = 0.75 and e (500 °C) = 0.05. A layer of CVD silicon nitride (750 Å) on the black film results in a = 0.91 and en (500°C) = 0.11. Both configurations have been tested for over 1000 hours at 500 °C in a roughing pump vacuum without measured deterioration.