INVESTIGATION OF THE BORON INCORPORATION IN POLYCRYSTALLINE CVD DIAMOND FILMS BY TEM, EELS AND RAMAN-SPECTROSCOPY

The incorporation of boron from B(C2H5)(3) in the gas phase during the low pressure diamond deposition in a hot-filament reactor is investig ated by various TEM techniques and Raman spectroscopy. Concentrations of B(C2H5)(3):CH4 up to 3800 ppm were used in gas phase, which gives b oron concentrations up to 3% in the layer according to SIMS measuremen ts. The characteristic Raman peak of diamond at 1332 cm(-1) remains ne arly unchanged up to very high boron concentrations when single {100} facets are investigated. However, peak shift and drastic intensity dec rease are connected with {111} facets. TEM shows diamond grains with d efect densities comparable to undoped layers even for the highest boro n concentration. Localized EELS spectra of this sample show the boron edge clearly for areas which can be attributed to growth on {111} face ts by the defect configuration. This signal is absent for grain segmen ts connected to growth on {100} facets, thus indicating inhomogeneous boron incorporation. Lattice dilatation of up to 0.3% is measured by C BED for crystal parts containing high boron concentrations. At the int erface between these and boron free parts strain contrast can be obser ved because of the different lattice constants. (C) 1997 Elsevier Scie nce S.A.