Estimation of the silicon concentration by an optical way in polycrystalline CVD diamond

Abstract

The concentration of radiative silicon centres in polycrystalline diamond films grown on silicon wafers was tentatively measured by their laser-induced luminescence (PL) at 1.681 eV. The total area under the PL line at room temperature is proportional to the amount of radiative Si point-defects in the volume excited by the laser beam. This amount was normalized to the area (expressed with the same arbitrary unit) under the diamond Raman line at 1332 cm -1 obtained simultaneously on the same set-up and compared to the absolute concentration determined by SIMS experiments. A linear relationship was obtained between the normalized PL area and the averaged SIMS values. Room temperature slope values (α laser ) of the linear relationship were obtained for the following laser lines: 632.8 nm, α 633 = 7.8 E + 15, 514.5 nm, α 514 = 2.5 E + 16 and for 488 nm, α 488 = 5.5 E + 16 at/cm 3 . SIMS profiles obtained in the different layers indicate that the distribution of silicon in the layers is a consequence of thermally activated diffusion from the silicon substrate during film growth.