Effect of grain size on optical and electrical properties of Ni80Fe20 thin films

In this investigation, the transmittance and electrical properties of NiFe thin films were measured under three conditions. NiFe thin films were sputtered on a glass substrate with a thickness (tf) from 300 Å to 1500 Å under the following conditions: (a) substrate temperature (Ts) maintained at room temperature (RT), (b) post-annealing at TA=150 °C for 1 h, and (c) post-annealing at TA=250 °C for 1 h. Transmission electron microscopy (TEM) demonstrated that the NiFe film yielded a strong face-centered cubic (FCC) (1 1 1) selected-area-diffraction (SAD) pattern. A spectral analyzer was utilized to measure transmittance through various thicknesses. Post-annealing treatment promoted the growth of grains, yielding a large average grain size, and therefore a small transmittance. However, electrical measurements revealed that increasing the electron mobility reduces the resistivity (ρ) and sheet resistance (Rs). At a thickness of 300 Å with post-annealing 250 °C, the optimal maximum transmittance is 50%; the optimal ρ is 110 μΩ cm, and the optimal Rs is 13 Ω/□. Accordingly, a 300 Å-thick NiFe thin film with favorable electrical and optical properties can be utilized in the components of a magneto-optical recording medium.