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Chemical vapour deposition and characterization of smooth -100-faceted diamond films.

Abscheidung und Charakterisierung glatter -100-facettierter Diamantschichten


Diamond and Related Materials 2 (1993), pp.158-168 : Abb.
ISSN: 0925-9635
Journal Article
Fraunhofer IAF ()
CVD diamond film; Diamantschicht; ion channeling; Ionenchanneling; Röntgentexturanalyse; Texturbildung; texture formation; X-ray texture analysis

Smoot (100)-faceted diamond films have been prepared by microwave-assisted chemical vapour deposition from CH4-H2 mixtures. Growth has been controlled by in-situ laser interferometry. Under appropriate growth conditions, the films show a fibre texture with the (100) fibre axis normal to the substrate. The surface is completely formed by well-aligned coplanar (100) facets. The structure and morphology of these films have been characterized by X-ray diffraction, ion channelling and angle-resolved optical scattering measurements. Fibre textures with an angular spread of the (100) directions as narrow as 1 degree have been observed. The coplanar (100) facets form an optically smooth surface, exhibiting pronounced specular reflection. The dependence of the texture formation and surface morphology on film thickness and deposition parameters, including substrate temperature and gas composition, has been studied. For lower than optimum growth temperatures the surface becomes rough as (111) fac ets develop in addition to the (still coplanar) (100) facets. For higher than optimum growth temperatures the size of the (100) facets increases and the texture axis tilts away from (100). By varying the gas composition, any texture axis between (100) and (110) can be established. Computer based growth simulations have been performed on the basis of evolutionary selection of specific crystallite orientations. It is shown that a growth parameter alpha=3 (exp 1/2) V100/V111, i.e. the ratio of the growth rates on (100) and (111) faces, determines the structure and morphology of the films. A novel two-step growth process based on the control of alpha permits the independent optimization of texture axis and surface morphology, offering the possibility to obtain smooth faceted diamond films for arbitrary film thickness.