ANALYSIS OF THE STRUCTURE OF MULTICOMPONENT CARBON-FILMS BY RESONANT RAMAN-SCATTERING

Diamond and carbonaceous films grown in a microwave assisted plasma re actor have been characterized by x-ray diffraction, scanning electron microscopy, and Raman spectroscopy. This study is mainly focused on th e identification of the different carbonaceous compounds which can coe xist with the diamond depending on the synthesis parameters. Selective etching reactions and the excitation wavelength dependence of Raman c ross sections of the different carbon species reveal that the broad an d poorly structured Raman spectra in the 1100-1700 cm(-1) region conta in six components that arise from three different carbonaceous species : (i) one species is graphitic and is identified from the components a t about 1350 and 1590 cm(-1) which are resonantly enhanced as compared to the other components when the excitation energy is lowered from 3 to 2 eV. (ii) The second species is associated with the two broad band s at 1350 and 1550 cm(-1) and is attributed to amorphous diamond-like carbon (a-C:H); both bands are resonantly enhanced by excitation energ ies in the range from 2.41 to 3.53 eV. These bands do not shift with e xciting energy. (iii) The third species is associated with a band cent ered at about 1470 cm(-1) and a weak band at 1150 cm(-1) This 1470 cm( -1) band overlaps with the 1550 cm(-1) band of the diamond-like compon ent, resulting in an apparent frequency down-shift when the incident p hoton energy decreases below the resonant enhancement range of the 155 0 cm(-1) band. Possible models for the structure of the third species are discussed.