Investigation of the dependence of optical band gap energy of amorph hydrogenated carbon thin films produced by single RF plasma method on plasma flow rate

In this study, the optical band gap energies of the a-C:H thin films produced by the plasma deposition technique was investigated. The plasma was produced under a frequency of 40 MHz using a 100 W electric power for 15 minutes under 0.2 torr plasma pressure. The thicknesses of the produced thin films were found to be 585 Å for a thin film produced at a flow rate of 2 cm3/minute, 758 Å for a thin film produced at a flow rate of 3 cm3/minute, and 684 Å for a thin film produced at a flow rate of 4 cm3/minute. It has become clear that there is no significant effect of the plasma frequency on the thin film thickness, and similarly it is not possible to establish a direct connection between the plasma flow rate and the film thickness. Films produced at flow rates of 2, 3 and 4 cm3/minute were subjected to optical transmission tests. The absorption coefficients depending on the wavelength and energy of the light used are calculated using the data obtained from the optical transmittance experiments for the thin films produced with each flow rate parameter. Using absorbance coefficients, the optical band gap energies of the produced thin films at the flow rates of 2, 3 and 4 cm3/minute were calculated to be 1.41 eV, 1.48 eV and 1.42 eV, respectively. The results obtained were also compared with the results obtained for thin films produced on similar conditions in the literature. A mathematical curve equation describing how the optical band gaps of the produced thin films depend on the gas flow rate parameter has been established. Using this equation, the production parameters for thin films that are likely to work with high efficiency in some wavelengths and energy values of the electromagnetic waves used in today's infrared communication technology were predicted. At the end of the study, a study proposal was presented to increase the usability of thin films in real life applications.