**2. Materials and Methods**

A CoFeW film with a thickness of 10–50 nm was sputtered onto a Si(100) substrate at room temperature by magnetron direct current (DC) sputtering with a power of 50 W power under the following three conditions: (a) the deposited films were kept at room temperature, (b) annealed at a treatment temperature (TA) at 250 ◦C for 1 h, and (c) annealed at 350 ◦C for 1 h. The chamber base pressure was 2 × <sup>10</sup>−<sup>7</sup> Torr, and the Ar working pressure was 3 × <sup>10</sup>−<sup>3</sup> Torr. The pressure under the ex-situ annealed condition is 3 × <sup>10</sup>−<sup>3</sup> Torr, and the selected Ar gas is used. The composition of the CoFeW alloy target was 40 at% Co, 40 at% Fe, 20 at% W. Furthermore, the structure of the CoFeW films was determined by using the grazing incidence X-ray Diffraction (GIXRD) patterns obtained by CuKα1 (PAN analytical X'pert PRO MRD, Malvern Panalytical Ltd, Cambridge, United Kingdom) and a low angle diffraction incidence at a two-degree angle. To determine the thickness accurately, a high-resolution cross-sectional field emission scanning electron microscopy (SEM, Hitachi SU 8200, Tokyo, Japan) was used to study the calibration thickness of the corresponding sputtering time. Before the measurement, the contact angle was properly air-cleaned on the surface. Then, the contact angles of CoFeW film were measured with deionized (DI) water and glycerol. The contact angles were then measured when the samples were removed from the chamber. Lastly, the surface energy was calculated based on the contact angle. The sheet resistance (Rs) was measured using a conventional fourpoint technique. The hardness and Young's modulus of the CoFeW film were measured

using the MTS Nano Indenter XP with a Berkovich tip. An indentation load of 1 mN was used to limit the penetration depth of the indenter to less than 10% of the film thickness. The indenter repeated the measurement at 10 positions for each sample. The indentation load was increased in 40 steps, and the indentation depth was measured at each step. Six indentations were studied in each sample, and the standard deviation was averaged to obtain more accurate results.
