A Study of the Anomalously High Infrared Absorption in Zinc Selenide Thin Films.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO SCHOOL OF ENGINEERING
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Low loss antireflection coatings for infrared laser windows have been found to have absorption coefficients three to four orders of magnitude higher than was predicted from bulk material properties. An investigation for the causes for this increase in zinc selenide was performed. Prior growth studies and theoretical descriptions of the growth process indicated that variations in stoichiometry could be a cause for the high absorption measured in the coatings. An experimental program in which zinc selenide coatings were deposited under a wide variety of conditions revealed that the infrared absorption of the coatings decreased as the deposition rate was lowered. Absorption of the coatings decreased as the deposition rate was lowered. This directly correlated with theoretical predictions based upon stoichiometry variations. Several surface and chemical analysis techniques indicated that the most probable cause for the abnormal absorption in the zinc selenide thin films was an increase in the zinc to selenium ratio which could be controlled to some extent by proper selection of vacuum deposition conditions. Author
- Lasers and Masers
- Infrared Detection and Detectors
- Solid State Physics