Effect of oxygen on the morphology of silicon deposits

In this work, a series of experiments were performed to study the effect of oxygen on the morphology of silicon obtained by electrodeposition from KCl‒K2SiF6 melt. SiO2 was chosen as the oxygen carrier. The concentration of the additive was determined from the results of the study of the effect of SiO2 additive on the concentration of free F‒ ions. According to the obtained dependence, assumptions about the nature of interaction between the components of the melt were made. The inflection points registered on the dependence ω(KF)‒ω(SiO2) indicate a change in the character of interaction of SiO2 with the investigated melt. Based on the results of the study of the kinetics of the cathodic process on glassy carbon, taking into account the theory of autocomplex structure, an assumption was made about the structure of discharging complex ions in KCl‒K2SiF6 and KCl‒K2SiF6‒SiO2 melts. The kinetics was investigated by cyclic voltammetry. When SiO2 was added, a broadening of the silicon discharge potential region was observed, as well as a disproportionate increase in the cathodic current with increasing SiO2 concentration in the melt. One of the possible explanations for the obtained results is the change in the structure of the discharging complex ions. The obtained data on the kinetics of the cathodic process, as well as assumptions about the structure of the discharging complex, became the basis for the choice of parameters of potentiostatic electrolysis. A series of experiments on electrodeposition of silicon from the studied melts at varying the value of cathodic overvoltage from 0.10 to 0.25 V were carried out during the research. The morphology of cathodic precipitates was investigated by electron‒scanning microscopy. It is assumed that changes in the morphology of the obtained cathodic precipitates are associated with changes in the structure of the discharging complexes.