Effect of Bias Voltage and Deposition Rate on the Structure and Coercivity of NiFe Films

Abstract

The effect of the bias voltage U_b and the deposition rate ${v}$ on the structure, grain size D, and coercivity H_c of NiFe films with a thickness d from 30 to 980 nm, grown on Si/SiO₂ substrates by DC magnetron sputtering, has been studied. In the case of U_b = 0, a decrease in ${v}$ from values ${v}$ ≈ 27 to ≈7 nm/min is accompanied by an increase in the values of the critical film thickness d_cr from d_cr ≈ 220 nm to d_cr ≈ 270 nm. In this case, H_c in films with d < d_cr is characterized by the dependence H_c ~ D⁶ and varies from ~1 to ~20 Oe. For U_b = –100 V, the effect of the deposition rate on the coercivity is much more noticeable. At ${v}$ = 7 and 14 nm/min, the films exhibit soft magnetic properties (H_c ≈ 0.15–1.4 Oe) and the absence of d_cr for the entire range of studied thicknesses. The films obtained at ${v}$ = 21 and 27 nm/min pass into the “supercritical” state at d ≥ d_cr ≈ 520 nm, and in the range d < d_cr they are characterized by the dependence H_c ~ D³ and an increase in the coercivity from ~0.35 to ~10 Oe.