Electrochemical synthesis of photoactive carbon-carbide structure on silicon in molten salt

Abstract

Carbon-carbide coatings on silicon with a distinctively developed surface were electrochemically synthesized in molten CaCl2 using Si-SiO2 precursor and a graphite anode. Energy-dispersive X-ray spectroscopy showed approximately one quarter of the structure (in at.%) was composed of carbon. X-ray diffraction identified crystalline phases of graphite, silicon carbide and carbonate. X-ray photoelectron spectroscopy identified the carbide/carbon concentration ratio varied from 0.2 in the external region of the structure to 0.7 at the silicon substrate boundary. Mott-Schottky analysis showed p-type semiconductivity of the structure with high density of charge carriers N > 1016 cm−3. The surfaces absorbed over 90% of white light in a broad region of wavelengths from 400 nm to 1100 nm. The obtained composite is promising for application as an antireflection and protective coating or a photoelectrode.