Optical properties of semiconducting carbon thin films electrodeposited on Silicon

Carbon thin films were deposited on Silicon (Si) substrates by electrolysis of methanol. The effect of camphor (C₁₀H₁₆O) - a natural source, incorporation in methanol is investigated. Camphor with varying amount (2%, 4%, 6% and 8%) was mixed in methanol solvent to prepare the electrolytes. Silicon substrates were mounted on the negative electrode. Remarkable change in the variation of current density as a function of applied potential was observed with camphor content. The films were characterized by optical microscopy, scanning electron microscopy (SEM), and optical transmittance/reflectance measurement by UV-VIS-NIR techniques. From optical microscopy and SEM micrograph sharp differences between deposited films are observed. FTIR spectra show absorption peaks in between 1250cm^-1 to 1750 cm^-1 which is the characteristic of diamond like carbon (DLC)/ amorphous carbon (a-C) films. From the transmittance/reflectance measurement of Si substrate samples for different percentage of camphor in methanol (0% and 6%) using UV-VIS-NIR technique it is found that the optical properties like optical transmittance, reflectance and absorption are different for different samples (due to change in camphor incorporation with methanol). And it is found that the optical band gap for Si substrate using only methanol solution is 1.1 eV then by adding 6% camphor into the solution it increases to 1.2 eV.