High-rate low-temperature (90°C) deposition of Ni-Zn ferrite films highly permeable in gigahertz range

Abstract

Ni-Zn ferrite films have been prepared by spraying a reaction solution of FeCl/sub 2/ + NiCl/sub 2/ + ZnCl/sub 2/ (pH = 6.8) and an oxidizing solution of NaNO/sub 2/ + CH/sub 3/ COONH/sub 4/ + NH/sub 4/ OH (pH = 6.8-9.2) simultaneously onto rotating glass substrates at a substrate temperature of 90/spl deg/C. The deposition rate increased with the pH value of the oxidizing solution, and a maximum deposition rate of 67 nm/min was attained at pH = 8.4. The film surface observed by scanning electron microscopy was smooth, and a high value of saturation magnetization M/sub s/ = 482 emu/cm/sup 3/ with a low value of coercivity H/sub c/ = 17 Oe were measured. The film showed a high static permeability /spl mu/' = 70 and very high magnetic resonance frequency f/sub T/ of about 900 MHz. The imaginary part of the permeability /spl mu/" was greater than 30 over a wide frequency range from 300 MHz to 3 GHz. Ni-Zn ferrite films prepared in this study should be useful not only for planar inductors but also as shielding materials for electromagnetic interference suppressions.