Ion-induced Ni/ferrite adhesion enhancement: 28Si + versus 40Ar + ion mixing

Abstract

The adhesion between 30 nm Ni films and ferrite substrates was examined as a function of the interfacial chemistry and mixing induced by low temperature 40Ar + and 28Si + ion mixing. The temperature of the Ni/ferrite specimens was kept between 50 and 100°C while the specimens were implanted with either 65 keV 40Ar + or 50 keV 28Si +. The doses of both types of implants were varied between 1 and 10×10 16 atom/cm 2. The interfacial mixing, interfacial chemistry and the Ni adhesion produced by the ion mixing processes was evaluated using XPS depth profiling, high resolution XPS and scratch testing, respectively. Both types of implants were observed to induce substantial interfacial grading, although this grading was greater for the 40r + than the 28Si + ion mixing. XPS analyses suggested that NiOM (where M is either Fe, Mn, or Zn) interfacial complexes were present in the as-deposited specimens, and that they were responsible for the relatively good adhesion (8 N) of the as-deposited films. These intrinsic interfacial complexes were destroyed by both the 40Ar + and the 28Si + ion mixing. In the case of 40Ar + ion mixing, no new interfacial complexes were produced. This resulted in the reduction of Ni/ferrite adhesion (to a critical force of 2 N). In the case of 28Si + ion mixing, new interfacial chemistry (NiSi, FeSi, and SiO) was produced, suggesting the formation of adhesive interfacial complexes (such as NiSiFeO and NiSiOFe). This new interfacial chemistry resulted in significant adhesion enhancements (up to 26 N).