The future of electrochemical deposition: nanomaterial building blocks
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FEATURE ARTICLE
The future of electrochemical deposition: nanomaterial building blocks Daniel Mandler 1 Received: 9 July 2020 / Revised: 9 July 2020 / Accepted: 10 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Introduction Since the beginning of electrochemistry in the nineteenth century, it has played a major role in the world of coatings. Electroplating, is the process, which uses an electric current to reduce dissolved metal cations to form a thin coherent metal coating on an electrode, has been developed by the Italian chemist Luigi Valentino Brugnatelli as early as 1805 using Volta’s battery [1]. Much later in 1833, Michael Faraday has treated electrochemical deposition (ED) in a more quantitative approach by what is known as the Faraday’s laws [2]. Since then, ED has become a widely used method for coating conducting surfaces by thin layers of mostly metals but also polymers, oxides, and much more. Nowadays, ED is a common method in the industry and is employed for coating miniature features, such as nanometer-size trenches of siliconintegrated circuits, i.e., by the Damascene process [3], as well as big objects in the automotive industry [4]. Moreover, additional methods such as electroless deposition have been developed and enable coating of non-conducting surfaces by a thin metallic layer. The common methodology of these ED approaches lies in the deposition solutions that contain ionic or molecular species. The current that passes through the electrode causes either the reduction or oxidation of these species and the formation of insoluble products, which deposit on the electrode surface. Since electron transfer is limited to a few nm from the electrode-electrolyte interface, the deposit follows closely the intimate structure of the surface, which allows the coating of complex geometries, e.g., screws, springs, and tools, by a well-controlled layer. In this respect and in spite of numerous papers and industrial processes involving ED, not much has
* Daniel Mandler [email protected] 1
Institute of Chemistry, The Hebrew University of Jerusalem, 9190401 Jerusalem, Israel
changed since the famous ED experiments of Brugnatelli and Faraday.
Electrochemical deposition of nanomaterials Conventional ED with all its advantages suffers from some significant drawbacks. It is quite difficult to control the structure of the deposit since the deposition of ions and molecules is usually isotropic. Thus, to form nano- and microstructures, other approaches, such as the application of templates, need to be integrated into the ED process. Moreover, the formation of coatings made of multi-elements, non-stoichiometric compounds, graded materials, uniform deposition and defect-free with excellent adhesion can be difficult with conventional ED, is limited and requires substantial efforts and development. It does not make sense to continue using ionic and molecular-based solutions for ED for many advanced applications or complex geometries. This is similar to building a house out of sand
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