Influence of Fluid Dynamics on the Electrochemical Deposition of Tantalum

Abstract

In the past decade there were many attempts for developing a method for the electrodeposition of refractory metals (Ti, Ta, Nb and W) at rather moderate temperatures employing ionic liquids [1]. Such tantalum thin coatings would exhibit advanced properties like excellent chemical and corrosion resistance and therefore have a large application potential e.g. in chemical process industry. This is why this metal has attracted the attention of many researchers aiming to develop new and cost-effective methods for its synthesis [2-5]. A special interest lies in developing an electrodeposition method with a quite simple procedure and high deposition rate, but with the ability to control precisely the layer thickness and quality. The deposition from ionic liquids proved more challenging than originally anticipated, e.g. when using halide precursors often sub-halides are formed instead of the metal [1-4]. Nevertheless, it has been shown recently that thin Ta metal layers can be deposited from ionic liquids [5, 6]. However, thicker coatings in the micrometer range and the accurate control of the crystallographic parameters remain challenging. The focus of this study is to investigate the influence of fluid dynamics (e.g. rotation, ultrasound) on the deposition of pure Ta metal. Furthermore, the in-situ microgravimetry is applied for investigating the influence of different electrochemical parameters on the Ta deposition rate. The deposited layers are characterized by Scanning Electron Microscopy and ex-situ scanning probe microscopy techniques. [1] A. Ispas, A. Bund, F. Endres, Application of the Electrochemical Quartz Crystal Microbalance for the Investigation of Metal Depositions from Ionic Liquids, ECS Transactions, 16 (2009) 411-420. [2] S. Zein El Abedin, H.K. Farag, E.M. Moustafa, U. Welz-Biermann, F. Endres, Electroreduction of tantalum fluoride in a room temperature ionic liquid at variable temperatures, Physical Chemistry Chemical Physics, 7 (2005) 2333-2339. [3] N. Borisenko, A. Ispas, E. Zschippang, Q. Liu, S. Zein El Abedin, A. Bund, F. Endres, In situ STM and EQCM studies of tantalum electrodeposition from TaF5 in the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, Electrochimica Acta, 54 (2009) 1519-1528 [4] A. Ispas, B. Adolphi, A. Bund, F. Endres, On the electrodeposition of tantalum from three different ionic liquids with the bis(trifluoromethyl sulfonyl) amide anion, Physical Chemistry Chemical Physics, 12 (2010) 1793-1803. [5] A. Ispas, A. Bund, Pulse plating of tantalum from 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide ionic liquids, Transactions of the Institute of Metal Finishing, 90 (2012) 298-304 [6] T. Carstens, A. Ispas, N. Borisenko, R. Atkin, A. Bund, F. Endres, In situ scanning tunneling microscopy (STM), atomic force microscopy (AFM) and quartz crystal microbalance (EQCM) studies of the electrochemical deposition of tantalum in two different ionic liquids with the 1-butyl-1-methylpyrrolidinium cation, Electrochimica Acta 197(2016)374–387