Observations of reaction zones at chromium/oxide glass interfaces

Abstract

Cr is often used in thin metallic film structures on oxide glasses since it exhibits good adhesion. The most likely explanation of the basic adhesion mechanism is the formation of a graded metal oxide layer at the interface. In general, details of the interface properties are needed to get a complete understanding of phenomena such as adhesion. We report here observations of interface structures using spatially resolved electron energy loss spectrometry with a small probe (2 Å) scanning transmission electron microscope. Two interfaces, evaporated Cr/alkaline earth boroaluminosilicate glass and sputtered Cr/barium boroaluminosilicate glass, are examined. As expected from the classical adhesion theory, very thin partially oxidized intermediate layers are seen in both samples. However, a 5 nm Cr diffusion layer is also found in the evaporated Cr/glass system (without heat treatment), but it appears absent in the sputtered Cr glass system (with heat treatment). This difference suggests that the mechanisms of the adhesion of Cr to oxide glass are dependent on interface history.