Interfacial adhesion of alumina thin films over the full compositional range of ternary fcc alloy films: A combinatorial nanoindentation study

• Published in: Materials & design Vol. 193; p. 108802
• Main Authors: Schoeppner, Rachel, Ferguson, Calum, Pethö, Laszlo, Guerra-Nuñez, Carlos, Taylor, Aidan A., Polyakov, Mikhail, Putz, Barbara, Breguet, Jean-Marc, Utke, Ivo, Michler, Johann
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-08-2020; Elsevier
• Subjects: Adhesion; Atomic layer deposition; Combinatorial materials; Nanoindentation; Sputtering; Thin films; Thin films; Atomic layer deposition; Combinatorial materials; Adhesion; Sputtering; Nanoindentation
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2020.108802

Combinatorial materials design of thin films allows one to investigate fundamental mechanic relationships and optimize films for engineering applications. Using a newly integrated shutter controller, specifically developed for precise control over coating design, ternary alloys with full compositional range can be deposited onto single wafers. Programmable shutters allow one to create multilayered thickness gradients of two or three different materials, which can then be annealed to create films with large compositional gradients. Two 50 nm fcc alloys (AlCuAu, AuAgPd) were magnetron sputtered onto (0001) sapphire wafers. The changing chemical composition across the wafer was investigated with energy dispersive x-ray spectroscopy and transmission electron microscopy. AlCuAu showed multiple phases and intermetallics across the wafer, whereas for AuAgPd a solid-solution was observed. Both alloys were coated with 400 nm Al2O3 (atomic layer deposition, ALD), to investigate their potential as adhesion layers for ALD coatings. Adhesion of the bilayers across the wafer was measured with instrumented nanoindentation, producing well-defined delamination-blisters. Small arrays of indents placed over the surface, each location corresponding to different adhesion layer compositions, illustrate adhesion-promoting properties of numerous interface compositions in single samples. For the two bilayer systems, adhesion mapping revealed the areas of optimum adhesion layer composition for best adhesion properties.
[Display omitted]
•Thin films with large compositional gradients were made by wedge deposition with programmable shutters and post-annealing.•50nm AuAgPd and AlCuAu ternary fcc alloys were sputter deposited on (0001) sapphire substrates.•Depending on the elemental composition, a solid solution (AuAgPd) or multiple phases (AlCuAu) were obtained across the wafer.•Alloy composition influences the growth kinetics of a 400nm Al2O3 top-coating grown via atomic layer deposition (ALD).•Nanoindentation mapping revealed the areas of optimum alloy composition for best adhesion properties of the bilayer systems.