半导体Si上电沉积Cu-Co颗粒膜及其巨磁电阻效应

采用电化学沉积方法在半导体Si上制备Cu-Co金属颗粒膜. XRD测试结果表明制备态的薄膜形成了单相亚稳态面心合金结构, 薄膜经退火后, XRD谱图中出现了析出的纯金属Co的衍射峰, 这表明薄膜在退火过程中发生了相分离. TEM测试结果也进一步证实了磁性的Co颗粒从非磁性的铜基体中析出. 随着退火温度的增加, 颗粒膜巨磁电阻(GMR)效应不断增大, 当退火温度为450 ℃时, Co0.20Cu0.80薄膜的巨磁电阻效应达到最大, 磁阻率为8.21％. 之后, 磁阻率又随退火温度的升高而降低. 退火前后样品磁滞回线的变化表明薄膜中发生了从超顺磁性到铁磁性的转变, 矫顽力、剩余磁化强度和饱和磁化强度均随退火温度的增高而逐渐增大. 超顺磁性颗粒的作用导致了GMR－H与M－H曲线的不同.

Electrodeposition of Cu-Co Granular Films on Semiconductor Si Substrate and Their GMR Effect

CoxCu1－x granular films were prepared by electrodeposition at room temperature on semiconductor Si substrate. XRD result revealed that the as-deposited films formed a single phase metastable fcc alloy structure. Pure Co fcc diffraction peaks were observed in XRD pattern of the annealed sample, indicating phase separation occurred upon annealing. TEM characterization also confirmed the precipitation of the magnetic Co particles from the Cu-rich matrix. The giant magnetoresistance(GMR) of the films was improved after annealing. The maximum MR ratio of 8.21% was obtained for Co0.20Cu0.80 thin film after annealing at 450 ℃ for 1 h. Hysteresis loops of the as-deposited and annealed samples indicated the change from superparamagnetic to ferromagnetic contribution to the GMR effect. The values of coercivity(Hc), remanent magnetization(Mr), saturation magnetization(Ms) increased with annealing temperature. The effect of supperparamagnetic particles resulted the difference between GMR－H and M－H curves.