Electrodeposition of silicon from fluoride melts

Electrochemical studies, mainly cyclic voltammetry, square wave voltammetry and chronoamperometry, were carried out to study the behavior of dissolved silicon species in molten LiF-KF with additions of K2SiF6 at temperatures from 550 to 800 °C. Electrolysis experiments were run at constant current to deposit pure silicon. Working electrodes of silver, tungsten and glassy carbon and cathodes of silver and silicon were used. The cathodic reduction of dissolved Si (IV) species to silicon was found to be diffusion controlled. Some influence of nucleation phenomena was observed on silver cathode substrates. High purity and good quality silicon deposits were obtained during galvanostatic electrolysis. One challenge is to reduce the inclusions of solidified electrolyte. Current efficiencies for silicon deposition were found to be in the range from 85 to 95%.