Intrinsic stress origin in high quality CVD diamond films

Anisotropic intrinsic stress in diamond films grown by microwave plasma che mical vapor deposition has been studied by Raman spectroscopy in conjunctio n with transmission electron microscopy (TEM). A series of films of 200 to 1400 mu m thickness were analyzed. The confocal Raman spectroscopy has give n detailed information on the stress distribution within individual grains of the films with a spatial resolution of a few microns. TEM analysis showe d that the main defects of the films are sets of parallel microtwin lamella : starting from grain boundaries and ending inside the grains. Near-surface micro-Raman mapping revealed the preferable adjacency of compressive and t ensile stress regions located on opposite sides of grain boundaries, while the depth analysis revealed stressed zones in different points of the bulk of these films. A mechanism of the extended (micron scale) stress generatio n due to formation of incoherent boundaries between coalescent crystallites is suggested using a model of edge dislocation structure of intergrain bou ndary.