Optical properties of DC arc-discharge plasma CVD diamond

摘要

Mid-infrared transmission and absorption in polycrystalline chemical vapor deposition (CVD) diamond films has been studied. Free-standing films were grown in a DC arc-discharge plasma torch apparatus. The intensity of a band near 3.5 $mu@m, which was assigned in previous work to a C-H bond-stretching mode, correlates with the hydrogen concentration. One symmetric and one antisymmetric stretching mode were observed, with frequencies corresponding to an sp$+3$/-bonded CH$-2$/ species. In some films, the hydrogen-related absorption was reduced below 1 cm$+$MIN@1$/. A broadband at 8 $mu@m scales in intensity with the 3.5-$mu@m band, suggesting its association with hydrogen as well. A sharp feature at 1,330 to 1,335 cm$+$MIN@1$/ tentatively is assigned to defect-activated absorption by O($Gamma@) phonons.