Investigation of the adhesion mechanism of NiCr layers on Al2 O3 and AlN substrates

Sputtered NiCr layers on Al₂O₃ and AlN substrates show a very high adhesive strength in pull tests. An effort was made to investigate, with analytical procedures, the adhesion mechanism responsible for this. For the characterization of the surfaces and layers, element analyses were carried out with X-ray photoelectron spectroscopy and Auger electron spectroscopy. High-resolution transmission electron microscopy (HRTEM) studies were performed on a qualitative basis in order to obtain lattice fringes and lattice images of the thin overlayer and the substrate in near-interface regions. The results obtained lead to the conclusion that, with both ceramics, the good adhesion is due to the chemical bonding between Cr, Al, and O