The electronic and optical properties of silicon carbide nanotubes (SiCNTs) have been investigated using tight binding calculations based on previous density functional theory (DFT) studies. The optical spectra of SiCNTs are dependent on the diameter and chirality and their energy gap (Eg) reduction shows dependence on radius and electric field. The Eg of SiCNTs decreases linearly with electric field until reaches zero and semiconductor metallic transition occurs. Based on the dependence of band gap reduction on radius and electric field strength, the Eg explained in terms of radius and electric field with an explicit relation
