Electrochemical ALD, developed in the Authors group, has been used to form a number of elemental deposits, including Cu, Pt, and Ag, by this group and others. ALD is a methodology where surface limited reactions are used in a cycle to form nanofilms of compounds or elements, one atomic layer at a time. Underpotential deposition (UPD) is generally used for surface limited reactions in the electrochemical form of ALD. However, in the formation of a pure element, it might be assumed that UPD could be used. However, use UPD of an element on itself is by definition impossible. The definition of UPD is that an atomic layer of one element can be formed on a second element, due to the formation of a stable surface compound or alloy, at a potential prior to, under, that used to deposit the element on itself. Because of this issue, surface limited redox replacement (SLRR) has been used to form elemental deposits. The SLRR involves UPD to form an atomic layer of a sacrificial element on the desired element. This atomic layer is then exchanged for the desired element by redox replacement of the sacrificial atomic layer in a solution of a precursor of the desired element. This process can then be repeated to form nanofilms of the desired element of a thickness dependent on the number of replacement cycles performed. Nanofilm growth of Cu, Ru, and Pt will be discussed, as a function of the deposition conditions: the sacrificial metal, the UPD potential used, and the coverage of the sacrificial metal atomic layer. Film growth has been characterized using in-situ STM, LEED and Auger, as well as EQCM and XRD. Deposits of Cu appear to grow in a layer by layer format. However, some problems have been encountered with the growth of Pt films, in that they appear to roughen quickly under some conditions.

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1. Nanofilm Formation Using Electrochemical Atomic Layer Deposition (ALD)