Creating textured surfaces using plasma electrolysis
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Creating textured surfaces using plasma electrolysis Zhiling Zhang, Mukul Dubey, David Galipeau, and Qi Hua Fan, Department of Electrical Engineering and Computer Science, South Dakota State University, Brookings, South Dakota 57007 James D. Hoefelmeyer, Department of Chemistry, University of South Dakota, Vermillion, South Dakota 57069 Ilham Y. Al-Qaradawi, Physics Department, Qatar University, P. O. Box 2713, Doha, Qatar Address all correspondence to Qi Hua Fan at [email protected] (Received 22 August 2013; accepted 22 November 2013)
Abstract Plasma electrolysis (PE) is a combination of electrolysis and plasma discharge. Previous studies indicated that PE usually created porous surface with irregular morphology as a result of the plasma–cathode interaction that was dominated by physical reactions. This paper demonstrated that highly ordered textured silicon surfaces could be created using PE. This abnormal anisotropic etching phenomenon implied that the chemical reactions were decoupled from the physical processes and the physical reactions were suppressed. Raman spectra confirmed that the textured silicon surface created by PE conserved the crystalline structure. Therefore, PE may lead to new process regimes for surface engineering.
Introduction Combining the characteristics of electrolysis and plasma discharge, plasma electrolysis (PE) has promising potential in surface engineering.[1–6] During PE, a gas sheath forms around one of the electrodes and discharge occurs due to the ionization in the gas sheath when a high voltage is applied. PE was first studied by Kellogg in 1950. His results showed that the gas sheath was formed due to solvent evaporation in addition to the formation of gas during electrolysis.[7] The ionization and plasma-induced chemical reactions were investigated during the 1960s by Hickling and Ingram. Their results suggested that the products of the PE were related to the electrolytes used.[8,9] This pioneering work prompted subsequent studies of both the basic science and practical applications of PE.[10–17] The identified main factors that influence the plasma discharge included applied voltage, electrolyte, reactor geometry, electrolyte temperature, and flow dynamics.[11,13–15] PE could occur on either cathode or anode. PE oxidation, which occurs on the anode, has been widely used to form oxide coatings on metals and alloys in order to enhance their performance such as wear, corrosion, and thermal barrier[16]; PE saturation (of the surface with other elements), which occurs on the cathode, has been used for surface cleaning, heat treatment, and deposition of metal and alloy coatings. A common feature of the interactions between the plasma and the working electrode was the formation of micro-/nano-particles and the creation of irregular microstructures in the surface of the solid electrode, either cathode or anode.[2,3,17] Previous studies indicated that the plasma–electrode interaction was due to the implosion of plasma bubbles as a
consequence of the cooling of the high-
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