EX-SITU SPECTROSCOPIC ELLIPSOMETRY STUDIES OF MICRON THICK CVD DIAMOND FILMS

Micron thick diamond films have been studied by spectroscopic ellipsom etry (SE). The films mere grown, on previously prepared Si(100) substr ates, by the plasma enhanced chemical vapor deposition (PECVD) techniq ue. Ex situ SE measurements were carried out on samples grown under di fferent conditions, such as substrate temperature and methane fraction in the gas mixture. An optical model consisting of five layers was co nstructed in order to explain the SE spectra and to provide the optica l and structural parameters of the films. This model was deduced from results of various measurements performed by other characterization te chniques (Raman spectroscopy, scanning electron microscopy, atomic for ce microscopy and positron annihilation spectroscopy) which have revea led the optical and structural parameters of the samples. Its sensitiv ity to the surface and interface roughness as well as to the absorptio n of the nondiamond phase of the film is demonstrated. Several values of the percentage of the nondiamond phase can be obtained, with the sa me fit quality, however, depending on the amorphous carbon reference u sed in the model. These references mere obtained by performing SE meas urements on various amorphous carbon films. Finally, our SE analysis h as allowed us to monitor the lateral homogeneity of the thickness, sur face and interface roughness and nondiamond phase concentration over t he diamond film.