Optical microscopic, synchrotron X-ray topographic and reticulographic study of homoepitaxial CVD diamond

Surface topography and crystal-lattice perfection of homoepitaxial layers d eposited by microwave plasma CVD on (0 0 1) and near-(0 0 1) facets polishe d on HPHT synthetic diamond are described. Optical micrographic techniques included birefringence, Nomarski and 2-beam interference. The synchrotron X -ray experiments comprised Laue topography plus a recently developed sensit ive misorientation-measuring technique, reticulography. Two special circums tances enhanced information yield from the experiments. First, the substrat e crystal was unusually strain-free and had a very low dislocation content. Second, epilayer growth had taken place in two stages, depositing thicknes ses of 10 mu m and 30-34 mu m, respectively. This double deposition complic ated the observations, but added features of scientific and practical inter est. Epilayer cracking finally present had occurred almost entirely before the second growth stage. With assistance from quantitative data provided by reticulography, the X-ray diffraction properties of the substrate and epil ayers are analysed. Lattice misorientations on the untreated lower surface of the substrate were only similar to 1 arcsec except dose to growth-sector boundaries and dislocation outcrops. The final epilayer growth surface abo ve areas where cracking in the first epilayer was absent or sparse exhibite d near-perfect-crystal diffraction behaviour. (C) 1999 Elsevier Science B.V . All rights reserved.