Ultraviolet Raman spectroscopy characterizes chemical vapor deposition diamond film growth and oxidation

The Raman spectra of diamond and chemical-vapor-deposition (CVD) diamond films in the UV have been excited within the diamond band gap at 228.9 nm for the first time. The lack of fluorescence in the UV-excited Raman spectrum of diamond and CVD diamond films allows Raman spectroscopy to monitor the carbon-hydrogen (C-H) stretching vibrations of the nondiamond components of the CVD film as well as the third-order phonon bands of diamond. The relative intensity of the C-H stretching bands at ∼2930 cm−1 to the diamond first-order phonon band at 1332 cm−1 is proportional to the atomic fraction of covalently bound hydrogen in the CVD diamond film. The third-order phonon band intensity and frequency maxima are very sensitive to the size of the diamond crystallite. Its intensity decreases, and the maximum shifts to lower frequency as the size of the diamond crystallite decreases. It is shown here that UV Raman diamond measurements have significantly greater information content than visible Raman measurements.