Ion-induced adhesion enhancement of Ni films on polyester: 84Kr + implantation

Abstract

The adhesion between 30 nm Ni films and poly[ethylene terephthalate] (PET) was examined as a function of the chemical and structural modification produced at the interface by 84Kr +implantation through the interface. 84Kr +implantation was performed to doses of 5 × 10 15, 1 × 10 16 and 5 × 10 16 Kr cm 2 using a 170 keV ion beam. During the implantation, the substrate temp kept below 100°C. The 84Kr + implantation produced some void and bubble formation at all doses. At 5 × 10 16 Kr cm 2 , the formation was so extensive that the Ni films were largely destroyed. Auger electron spectroscopy (AES) depth profiles and cross-sectional transmission electron microscopy (XTEM) analysis showed that the interface between the as-deposited Ni films and the PET substrates was very sharp. After 5 × 10 15 or 1 × 10 16 Kr cm 2 implantation, large quantities of C from the substrate, mixed into the Ni films, resulting in a film stoichiometry very close to nickel carbide (Ni 3 C). Despite this extensive interfacial mixing, the interface between the films and the substrates remained sharp. Although X-ray photoelectron spectroscopy (XPS) and electron diffraction (ED) analyses showed Ni 3C formation in the ion mixed films, there was no indication of any chemical bonding across the interfaces. Despite the extensive interfacial mixing and the hardening of the PET surface produced by the 84Kr +bombardment, adhesion evaluations, performed using a scratch test in conjunction with SEM and AES analysis, showed no significant adhesion increases. The Ni films were removed at forces below the minimum force (1 N) applied by the scratch tester for both the as-deposited and the ion processed specimens. This absence of adhesion enhancement after 84Kr + implantation is in direct contrast to the large adhesion enhancement previously observed following 28Si +implantation. It is concluded that substrate toughening and the mechanical interlocking of film and substrate have little influence on the adhesion of Ni films on PET.