Influence of annealing temperature and polymer substrate type on the structural, magnetic, mechanical, and electrical properties of Ni₈₀Ce₂₀ thin films for flexible electronics applications

Nickel-cerium (Ni₈₀Ce₂₀) thin films with thicknesses ranging from 10 nm to 50 nm were deposited onto polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA) substrates via direct current (DC) magnetron sputtering at room temperature (RT), followed by annealing at 40°C and 80°C. The films were characterized using various techniques, including grazing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM), magnetic force microscopy (MFM), vibrating sample magnetometry (VSM), nanoindentation, Hall effect measurement, and optical transmittance. XRD results revealed crystallization and improved atomic ordering with annealing, with a substrate-dependent crystallographic orientation observed nickel (Ni) (110) on PET and NiCe (220) on PMMA. Surface roughness decreased with annealing, more significantly for PET-based films. Magnetic domain analysis showed a transition from striped to wavy structures, enhancing domain stability. Magnetic properties, including saturation magnetization (Ms) and coercivity (Hc), varied with annealing temperature and substrate type. Mechanical properties, such as hardness and Young's modulus, increased with film thickness and annealing, with higher values observed for thicker films and those annealed at 80°C. The electrical properties, such as sheet resistance and resistivity, exhibited a decrease with increasing film thickness and annealing temperature, which can be attributed to enhanced crystallinity and reduced electron scattering. These findings provide insights into the influence of annealing and substrate type on the structural, magnetic, mechanical, and electrical properties of Ni₈₀Ce₂₀ thin films for potential applications in flexible electronics.