Magnetic Properties and Growth Behavior of Nd–Fe–B Films on Si(111)

• Published in: Japanese Journal of Applied Physics 1999-07, Vol.38 (7R), p.4051
• Main Authors: Tsai, Jai-Lin, Chin, Tsung-Shune, Shih, Shi-KunChen
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.38.4051

NdFeB films were prepared by dc-magnetron sputter-deposition onto Si(111) at 600 to 700°C. Anisotropic films with remanence ratio larger than 0.67 and intrinsic coercivity greater than 7 kOe were obtainable at a substrate temperature of 650°C on Si(111) using one of W, Mo, or Pt as the underlayer. The mechanical polishing can reduce the film thickness from about 850 nm to 150 nm, and the coercivity remains 2–5 kOe. The coercivity of being strongly dependent on film thickness can be explained by the domain-wall motion in films through suitable modeling. The depth-profile and microstructure of the films on different underlayers were explored by secondary ion mass spectroscopy (SIMS) and high resolution transmission electron microscopy. The Pt underlayer, being in fact a Pt/Ti/SiO 2 /Si(111), is a sound barrier layer between the NdFeB film and Si(111) so that there is negligible interdiffusion as evidenced by SIMS depth profile. The formation of silicide was found in films with Mo or W underlayer sputtered at 650°C. This can be observed from the overlap region between the underlayer and Si(111) in the SIMS depth profile. Diffusion coefficients of the Nd, Fe, B in Si(111) were also quantitatively estimated.