Surface Technology, 13 (1981) 331 - 337 331 ELECTROCOATING OF SILICON AND ITS DEPENDENCE ON THE TIME OF ELECTROLYSIS GOPALAKRISHNA M. RAO, DENNIS ELWELI. and ROBERT S. FEIGELSON Center for Materials Research. 105 McCullough Building, Stanford University, Stanford, (?A 94305 (U.S.A.) (Received December 29. 1980) Summary Silicon was electrocoated onto silver at a constant current density of 25 mA cm 2 from a solution of 12 mol.(}~ K2SiF(, in KF LiF eutectic at 750 + 5 C for plating times of up to 16 h. Uniform coherent films with good adherence were obtained at various plating times longer than 2 h. Elec- trolysis for less than 2 h gave non-uniform films on the face of the silver substrate even though the edges were completely covered. The thickness of the film varied linearly with the time of electrolysis and the growth rate was 10 tam h 1.The morphology of the coatings and the use of electrodeposited silicon in solar cell technology and in corrosion protection are discussed. 1. Introduction The search tbr cost-effective silicon layers suitable for terrestrial photovoltaic energy conversion has led to a proliferation of silicon sheet crystallization techniques [1 - 3]. Moreover, silicon coating is a method of forming hard layers with good mechanical properties and corrosion re- sistance on various materials at both normal and elevated temperatures [4, 5]. Electrodeposition of silicon offers some unique advantages over conventional processes. The process can be operated at relatively low temperatures in comparison with those which involve molten silicon and can yield a product which has a substantially lower impurity concentration than the source material. Plating of areas or complex shapes is relatively easy. With the exception of work in our laboratory [2, ;5, 6], previous work on silicon electrodeposition has invariably yielded dendritic or powdery deposits [7, 8]. Cohen [6] has been able to electroplate coherent epitaxial layers of silicon at very low current densities (much less than 10 mA cm- 2) using dissolving silicon anodes. Recently we reported success in electro- winning thick (several millimeters) coherent dense silicon layers with good adherence on silver [2] and graphite [3] substrates. 0376-4883/81/0000-0000/S02.50 t Elsevier Sequoia/Printed in The Netherlands