Effect of co-deposited iron on microstructures and properties of electroplated nanocrystalline nickel-iron alloys

Nickel-iron nanocrystalline alloys with different compositions and grain sizes were fabricated by electroplating for microelectromechanical system (MEMS). The iron content of the deposits was changed by varying the nickel/iron ion ratio in the electrolyte. X-ray diffraction (XRD) analysis was applied for measuring the strength of the texture and the grain size of deposits. The nickel/iron atom ratio of deposits was analyzed by EDS. The hardness of the alloys was evaluated by Vickers hardness indenter. The internal stress of the deposits was measured by thin film stress measurement using Stoney's formula. Surface morphology and roughness were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Hardness and internal stress mechanism of the electroplated structure as a function of Fe ion content and current density were revealed. With the increase of iron content, the hardness and internal stress of deposits increase. An excellent correlation between the increase in the internal stress and the loss of (200) texture was found.