While various layer schemes have been developed to protect thin film silver mirrors from tarnish and corrosion, the mechanisms by which these protective layers improve mirror durability are not fully understood. Mixed flowing gas exposure of plasma beam sputtered silver mirrors was used to investigate how the composition of the very thin adhesion layer changes the mechanism of corrosion feature growth. Two model mirror coatings were analyzed in which the composition of the base layer below the silver and the adhesion layer above were varied. Optical measurements and microscopy, SEM, TEM, and EDS were used to characterize the compositional and chemical effects at the layer interfaces. Large circular corrosion features formed along the silver-chromium interfaces; the addition of nickel to the layers on either side of the silver limited the growth of these features, but resulted in the corrosive attack of the silver itself.
Electron BackScatter Diffraction (EBSD) is a relatively new, scanning electron microscope-based technique used to characterize microstructures and textures in crystalline metal and ceramic materials. Advances in SEM technology, especially the development of field emission SEMs, as well as in EBSD detector design have allowed characterization at the sub-10 nm level. This paper gives a basic introduction to the EBSD technique with applications on materials with microstructures on the micron and sub-micron scale. Automated EBSD mapping at these and other resolution levels is used to study texture, individual grain orientation, crystallography-based phase identification, grain size, grain shape, strain state, grain boundary character, area percentages of multiple phases in bulk samples, crystallography of facets and failure initiation sites, and other materials characteristics. Sample sectioning and polishing are often necessary for mapping microstructures in bulk samples, however as-grown structures such as thin films and interconnects are suitable for mapping as is, and “point & shoot” type analyses may be used on other unprepared samples in conjunction with SEM imaging for phase identification and basic crystallographic orientation studies. For micron-scale devices and components, EBSD-equipped dual beam FIBs are used to select cross-sectional planes of analysis with high precision.