Epitaxial Ir layers on SrTiO3 as substrates for diamond nucleation: deposition of the films and modification in the CVD environment

Iridium films on SrTiO3(001) have recently proven to be a superior substrat e material for the heteroepitaxy of diamond thin films by chemical vapour d eposition in the effort towards the realization of single crystal diamond f ilms. In this paper we report on the growth and structural properties of ir idium (Ir) films deposited by electron-beam evaporation on SrTiO3(001) surf aces varying the deposition temperature between 280 and 950 degrees C. The films were studied by scanning electron microscopy, atomic force microscopy and X-ray diffraction. At the highest temperature film growth proceeds via three-dimensional nucleation, coalescence and subsequent layer-by-layer gr owth. The resulting films show a cube-on-cube orientation relationship with the substrate and a minimum mosaic spread of 0.15 degrees. Towards lower d eposition temperatures the orientation spread increases only slightly down to similar to 500 degrees C while the surface roughness, after passing thro ugh a maximum at similar to 860 degrees C, decreases significantly. For the lowest temperatures (below 500 degrees C) the mosaic spread rises accompan ied by the occurrence of twins until the epitaxial order is lost. plasma tr eatment in the diamond deposition reactor at high temperature (920 degrees C) yields low nucleation densities and modifies the Ir surface. At the same time {111} facets show a significantly higher structural stability as comp ared with {001} facets. Nucleation at 700 degrees C results in highly align ed diamond grains with low mosaic spread and a vanishing fraction of random ly oriented grains, proving the superior properties of Ir films on SrTiO3 f or diamond nucleation as compared with pure silicon substrates. (C) 2000 El sevier Science S.A. All rights reserved.