Film stress and magnetic properties of nickel, cobalt, iron and iron-cobalt alloy electrodeposits

Nano-/Micro-ElectroMechanical Systems (NEMS/MEMS), including microactuators, sensors, micromotors and frictionless microgears use magnetic materials, because electromagnetically-actuated NEMS/MEMS are more stable for high force and large actuation gap applications. In addition to NEMS/MEMS, there is also great interest in fabrication of nanostructured magnetic materials (e.g., multilayers, nanowires, nanotubes, nanorods and nanoparticles) to apply in nanodevices, including nanoelectronics, spintronics, drug delivery and bioseparation. In order to integrate magnetic materials to devices, properties (e.g., magnetic, mechanical and electric properties, film stress and corrosion resistance) and deposition processes (e.g., operating temperature, pH) must be "tailored". In particular, good magnetic properties with minimum film stress are essential for magnetic materials for successful integration to magnetic-NEMS/MEMS. In the present studies, various low-stress iron group metals and iron-cobalt alloy thin films were developed. The effect of deposition parameters on film compositions, surface morphology, magnetic properties and film stress of electrodeposits were investigated using scanning electron microscopy (SEM), the flexible strip method and vibrating sample magnetometry (VSM). In general, low stress iron group metals and iron-cobalt alloys were electrodeposited by applying low current density and high operating temperature in an additive-free acidic chloride bath. Magnetic properties including coercivity and squareness were strongly influenced by film stress.