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

用XRD和SEM研究了恒电流条件下电沉积钴的介观结构，结果表明：（1）硫酸盐溶液中的钴沉积层由规则的六方片晶组成，在高电流密度和高温下均呈现（002）择优取向;另一方面，在低电流密度和低温下观察到（110）面的优势取向。Pangarov提出的二维形核假说阐明了电沉积金属的择优取向与沉积过电位之间的关系，从而很好地解释了上述结果。然而，与上述假设相反，（001）和（112）面都没有优先取向于高过电位区。这似乎是由电荷-质量转移的速率决定步骤的变化引起的。(2)从氯化物镀液中沉积的钴的介观结构与从硫酸盐镀液中沉积的钴的介观结构有很大不同。也就是说，优选的（110）取向在显著宽的电解条件范围内显示。这表明在电沉积过程中形成的中间体的结构被氯离子的存在改变。(3)在界面附近观察到电沉积钴与基体之间的外延关系。随着电解过程中库隆布量的增加，存款厚度的影响逐渐减弱，出现了电解条件所固有的介观结构。（4）氯离子对沉积物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.