IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Thin Films Tuesday Sessions
       Session TF-TuM

Paper TF-TuM5
Kinetics of Hydrogen Induced Changes of Optical Properties in Smart Coatings

Tuesday, October 30, 2001, 9:40 am, Room 123

Session: Optical Thin Films
Presenter: M. Wuttig, Aachen University of Technology, Germany
Correspondent: Click to Email
Certain transition metal oxides and hydrides show remarkable changes of their optical properties upon hydrogen exposure, in particular if the film surface is covered by a thin Pd or Pt film. This effect can be used to create window coatings that enable a switching of optical properties. In this study we compare the switching kinetics of several thin film systems including Mg, Gd, MgGd alloys and WO@sub 3@ upon hydrogen exposure. The switching process is studied in-situ by time resolved optical spectroscopy measurements, x-ray diffraction and x-ray reflection as well as mechanical stress measurements. The latter measurements reveal that for the different materials very different stresses arise as a function of hydrogen exposure. The lowest stresses are observed for WO@sub 3@ films, while stresses above 1 GPa were observed for Gd. Nevertheless the value of the stress change alone is insufficient to determine if plastic deformation and degradation of the films upon hydrogen exposure takes place. The influence of the film morphology on switching kinetics is carefully studied. A particularly pronounced correlation between switching kinetics and film density is observed for the WO@sub 3@ films where the time constant varies by more than two orders of magnitude upon a variation in density by 20%.