STRUCTURAL AND OPTICAL-PROPERTIES OF AMORPHOUS HYDROGENATED FLUORINATED CARBON-FILMS PRODUCED BY PECVD

Fluorinated films were deposited from radiofrequency discharges of tol uene/trifluorotoluene and toluene/sulfur hexafluoride mixtures. Actino metric optical emission spectroscopy was used to determine trends in t he concentrations of the plasma species H, CH, and F as a function of the partial pressure of trifluorotoluene or sulfur hexafluoride presen t (expressed as a percentage of the total chamber pressure) designated R-T and R-s, respectively. Transmission infrared spectrophotometry an d electron spectroscopy for chemical analysis revealed that the films contain various fluorine-containing functionalities and that the degre e of fluorination increases as R-T or R-s is increased. Ultraviolet-vi sible spectrophotometry of films deposited at various values of R-T an d of R-s allowed the determination of the absorption coefficients ct o f the films. From plots of ct as a function of photon energy it was po ssible to calculate the optical gap (E-04). An intriguing result was a decline and subsequent rise in E-04 as R-s was increased. Molecular m odelling using ZINDO/PM3 calculations provided a semi-quantitative exp lanation of the dependence of E-04 on R-s. (C) 1997 Elsevier Science S .A.