Study of the interface microstructures of CVD diamond films by TEM

The characteristics of the interface microstructures between a CVD diamond film and the silicon substrate have been studied by transmission electron m icroscopy and electron energy loss spectroscopy. The investigations are per formed on plan-view TEM specimens which were intentionally thinned only fro m the film surface side allowing the overall microstructural features of th e interface to be studied, A prominent interfacial layer with amorphous lik e features has been directly observed for CVD diamond films that shows a hi ghly twinned defective diamond surface morphology, Similar interfacial laye rs have also been observed on films with a (100) growth texture but having the {100} crystal faces randomly oriented on the silicon substrate. These i nterfacial layers have been unambiguously identified as diamond phase carbo n by both electron diffraction and electron energy loss spectroscopy. For t he CVD diamond films that exhibit ht heteroepitaxial growth features, with the {100} crystal faces aligned crystallographically on the silicon substra te, such an interfacial layer was not observed. This is consistent with the expectation that the epitaxial growth of CVD diamond films requires diamon d crystals to directly nucleate and grow on the substrate surface or on an epitaxial interface layer that has a small lattice misfit to both the subst rate and the thin film material.