Department of Chemical and Biomolecular Engineering, University of California at Berkeley, Berkeley, California 94720, USA.
ACS Appl Mater Interfaces. 2011 May;3(5):1581-4. doi: 10.1021/am200144k. Epub 2011 Apr 15.
Galvanic displacement (GD), a type of electroless deposition, has been used to obtain ultrasmooth gold thin films on silicon <111>. The novel aspect of the method presented herein is the absence of fluoride ions in the liquid phase, and its principal advantage when compared to previous efforts is that the process is inherently self-limiting. The self-limiting factor is due to the fact that in the absence of fluorinated species, no silicon oxide is removed during the process. Thus, the maximum gold film thickness is achieved when elemental silicon is no longer available once the surface is oxidized completely during the galvanic displacement process. X-ray photoelectron spectroscopy has been used as a tool for thickness measurement, using the gold to silicon ratio as an analytical signal. Three gold plating solutions with different concentrations of KAuCl₄ (2, 0.2, and 0.02 mM) have been used to obtain information about the formation rate of the gold film. This XPS analysis demonstrates the formation of gold films to a maximum thickness of ∼3.5 Å. Atomic force microscopy is used to confirm surface smoothness, suggesting that the monolayer growth does not follow the Volmer-Weber growth mode, in contrast to the GD process from aqueous conditions with fluorinated species.
电置换（GD）是一种无电镀技术，已被用于在硅<111>上获得超平滑的金薄膜。本文所提出方法的新颖之处在于液相中不含氟离子，与以往的努力相比，其主要优点是该过程本质上是自限制的。自限制因素是由于在没有氟化物质的情况下，在电置换过程中不会去除氧化硅。因此，一旦在电置换过程中表面完全氧化，当元素硅不再可用时，达到最大金膜厚度。X 射线光电子能谱（XPS）已被用作厚度测量的工具，使用金与硅的比率作为分析信号。使用三种不同浓度的 KAuCl₄（2、0.2 和 0.02 mM）的镀金溶液来获取有关金膜形成速率的信息。XPS 分析表明金膜的形成厚度最大可达约 3.5 Å。原子力显微镜（AFM）用于确认表面平滑度，表明单层生长不遵循弗伦克尔-韦伯生长模式，与含有氟化物的水溶液中的 GD 过程相反。
