CONTROL OF MESOSCOPIC STRUCTURE OF ELECTRODEPOSITED IRON-GROUP METAL FILM BY DEPOSITION OVERPOTENTIAL

采用XRD和SEM对恒流条件下电沉积钴的介观结构进行了研究。所得结果如下：(1)硫酸盐浴中的钴矿床由定义明确的六边形片状物组成，在高电流密度和高温下均形成首选（002）取向。另一方面，在低电流密度和低温下观察到（110）平面的优势取向。这些结果可以用Pangarov的二维成核假说很好地解释，该假说澄清了电沉积金属的择优取向与沉积过电位之间的关系。然而，与上述假设相反，（001）和（112）平面都没有优先定向在高过电位区域。这似乎是由电荷到质传递的速率决定步骤的变化引起的。(2)氯化物浴沉积钴的介观结构与硫酸盐浴沉积钴的介观结构有很大的不同。也就是说，优选的（110）取向在很大范围的电解条件下显示出来。这表明氯离子的存在改变了电沉积过程中形成的中间体的结构。(3)电沉积钴与衬底之间在界面附近存在外延关系。随着电解通过库仑量的增加，镀层厚度的影响逐渐减弱，电解条件固有的介观结构出现。(4)氯离子对镀层的择优取向和形貌有显著影响。(5)沉积钴的形貌与其择优取向密切相关。

The mesoscopic structure of cobalt electrodeposited under galvanostatic conditions was investigated using XRD and SEM.The results obtained are to be as follows ;(1) The cobalt deposits from sulfate baths consisted of well-defined hexagonal platelets, resulting in the preferred (002) orientation at both high current density and high temperature. The predominant orientation of (110) plane was observed, on the other hand, at low current density and low temperature. These results was able to be well explained by Pangarov's two-dimentional nucleation hypothesis which clarify the relationship between the preferred orientation of electrodeposited metals and the deposition overpotential. However, contrary to the above hypothesis, neither (001) nor (112) planes were preferentially oriented over high overpotential region. This seems to be caused by the change in the rate-determining step to the charge- to mass-transfer.(2) The mesoscopic structure of cobalt deposited from the chloride baths was quite different from the one from the sulfate baths. That is to say, the preferred (110) orientation was shown over significantly wide range of electrolysis conditions. This suggests that the structure of the intermediated formed during the electrodeposition process was changed by the presence of chloride ion.(3) Epitaxial relationship between the electrodeposited cobalt and the substrate was observed in the vicinity of their interface. The effect of the deposit thickness gradually diminished with increasing the amount of coulombs passed during electrolysis and the mesoscopic structure inherent to the electrolysis condition appeared(4) Chloride ions significantly affected the preferred orientation as well as the morphology of the deposits.(5) The morphology of the deposited cobalt was closely correlated with its preferred orientation.