A novel electrochemical exfoliation route to tailor the graphene bandgap through silicon incorporation: semi-metallic to semiconducting transition

Abstract

Graphene–silicon (Gr–Si) composites were produced by powder compaction, low-temperature sintering, and subsequent electrochemical exfoliation, which was further improved to provide materials with variable band gaps for semiconductor applications. By systematically varying the graphene-to-silicon precursor ratios (85 : 15, 80 : 20 and 75 : 25), the optical bandgap was successfully modulated from 1.25 eV to 1.56 eV, accompanied by a conductivity variation between 1.033 and 1.223 S m⁻¹. Structural and chemical characterization using XRD, Raman spectroscopy, FTIR spectroscopy, UV-vis spectroscopy, FESEM/EDX and thermal analysis revealed that silicon incorporation induces Si–O–C interfacial bonding and partial sp² → sp³ rehybridization, leading to disruption of the π-electron network and progressive bandgap opening. Graphene-rich composites exhibited higher electrical conductivity, whereas silicon-rich compositions demonstrated enhanced thermal stability due to the formation of silica-like passivation layers. This scalable synthesis route establishes a direct structure–bandgap–conductivity correlation and highlights the potential of Gr–Si composites for optoelectronic, photovoltaic and next-generation semiconductor devices.