Raman and photoluminescence microscopy mapping of CVD micro-diamonds

Abstract

Abstract A triple monochromator micro Raman spectrometer with multichannel CCD detection and confocal entrance optics was used to study the distribution of different carbon modifications and photoluminescence centers on hot filament CVD diamond samples with sub-μm lateral resolution. The diamond nucleation density on the clean (100) silicon surfaces was about 106 cm−2. Therefore, our experiments study individual diamong crystallites with up to 5 μm in size. Using single point micro Raman measurements, the relative Raman intensity from the different carbon modifications seems to vary from crystallite to crystallite. From a Raman mapping, the origin of this behaviour becomes clear—an inhomogeneous distribution of non-sp3-bonded carbon for each diamond crystallite. Therefore, a single point high lateral resolution confocal micro-Raman measurement on a CVD-diamond crystallite of a size of larger than 1 μm does not represent the properties of the whole crystallite. The information from a Raman mapping or at least a linescan experiment is necessary to compare properties of such crystallites, for example in different positions on a sample. The inhomogeneous distribution of sp2-bonded carbon is assumed to be correlated to the different defect incorporation in the various growth sectors (faces) of the individual diamond crystallites. In addition the luminescence intensities of the Si-related center at 1.68 eV and of a broad band around 2 eV were used to generate a map of photoluminescence intensities for isolated diamond crystallites, as well as for a stripe of closed diamond film in the close neighbourhood, grown on a defect of the silicon substrate surface.