Working Pressure Dependence of Properties of Al₂O₃ Thin Films Prepared by Electron Beam Evaporation

The effects of working pressure on properties of Al₂O₃ thin films are investigated. Transmittance of the Al₂O₃ thin film is measured by a Lambda 900 spectrometer. Laser-induced damage threshold (LIDT) is measured by a
Nd:YAG laser at 355nm with a pulse width of 7ns. Microdefects were observed under a Nomarski microscope. The samples are characterized by optical properties and defect, as well as LIDT under the 355nm Nd:YAG laser radiation. It is found that the working pressure has fundamental effect on the LIDT. It is the absorption rather than the microdefect that plays an important role on the LIDT of Al₂O₃ thin film.