FIELDMAP OF MORPHOLOGY OF DIAMOND FILMS GROWN BY USE OF DC PLASMA GLOW-DISCHARGE CHEMICAL-VAPOR-DEPOSITION

We have studied the morphology and texture of CVD diamond films grown by d.c. plasma glow discharge CVD by means of SEM analysis and X-ray d iffraction. This works follows a preliminary work on morphology change s from disordered to textured structure with a thorough investigation in a wide interval of substrate temperature, 955-1150 degrees C, and m ethane into hydrogen volume concentration, 0.9-3.8%. The other deposit ion parameters have been kept constant: overall pressure, 210 Torr, ga s flow rate 300 seem, power density, 38 W mm(-2). Care has been taken to prepare the substrate with a standard procedure in order to avoid u nreproducible effects on nucleation and growth. In-plane texture has b een determined by calculating the average percentage of oriented grain s from the area of the Bragg peaks and the powder diffraction data. Th e results of this quantitative analysis confirm the SEM morphology obs ervation. A fieldmap has been developed for the him morphology and tex ture as functions of substrate temperature and methane concentration i n order to give an useful information for directing the CVD process by means of this particular method. Moreover a qualitative agreement wit h previously reported data supports the hypothesis that the morphology does not depend on the particular CVD method but only on the depositi on conditions, i.e. the deposition parameters and the activation of th e reactant gases. The density of nucleation has been also studied by S EM analysis, leading to conclude that there is no competition between grains and evolutionary growth for the used deposition conditions, res ulting in grain sizes within the same order of magnitude of the film t hicknesses. A clear correlation has been found between the rate of gro wth of the films and their texture, in the sense that maxima and minim a of the rate of growth always correspond to maxima in the diamond tex ture. A thorough explanation of this correlation will require further ad hoc investigations. (C) 1998 Elsevier Science S.A. All rights reser ved.