Strategies for the Layer-by-Layer Electrodeposition of Ultra-Thin Metal Films.

摘要

The formation of metallic over-layers and over-layer alloys has long been the focus of many academic communities. Epitaxial over-layers provide unique properties with respect to their bulk properties, and have also shown thickness dependence. In addition to this metallic ultrathin over-layers and over-layer alloys provide for more efficient material utilization given that atoms are generally present at the surface of the material, allowing for more efficient reactivity. These benefits necessitate a technique that has the ability to simply form metal over-layers of various types, compositions, and thicknesses with fine control. It is for these reasons that electrodeposition techniques such as, surface limited redox replacement, surfactant mediated growth, and self-terminated deposition have been developed to simply and controllable deposit metal over-layers on a variety of substrates.;This work will detail the development of new techniques (ESLRR) and the application of existing techniques to new systems, Au on Cu and Pt on Au, for the controlled deposition of ultra-thin epitaxial over-layers on a variety of substrates. Electroless Surface Limited Redox Replacement (ESLRR) will be described both at a proof of concept level, for the deposition of Ag on Au, and at the applied level for the deposition of Pt on Au. It will be shown that film grown via ELSRR of comparable to superior quality to those prepared via other methods.;The spontaneous deposition of Au on Pt will also be explored. It will be shown that this system operates via a hybrid mechanism involving both, the electroless reduction of Au via Pt oxide formation, as well as the formation of an ordered [AuCl4]- ad-layer, that can be later reduced via potential application.;Finally it will be shown that the deposition of Au on Cu results in alloy formation via a potential controlled galvanic displacement and mixing mechanism. This will be demonstrated via electrochemical characterization and stripping, morphological analysis, and elemental analysis via XPS. It will be shown that regardless of the deposition protocol, in Cl- containing electrolyte there is little deposit passivation, however if the system is studied utilizing and alternative complexing agent (S2O3-) then more complete alloying and mixing results.