-textured diamond thin film on a rough and randomly oriented Al<SUB>2</SUB>O<SUB>3</SUB> substrate has been achieved by MPCVD. The cyclic technique--the cyclic modulation of the H<SUB>2</SUB> plasma (etching process) and CH<SUB>4</SUB>+H<SUB>2</SUB> plasma (growing process)--has been applied during the growth stage with various etching/growth time ratios. The dependencies of properties and morphologies of the films on the etching time interval were well explained by the selective etching of hydrogen ions to non-- oriented grains. The strong effects of different methane concentrations and substrate temperatures on the -textured growth were also concluded. Growth mechanisms of -textured diamond thin films on Al<SUB>2</SUB>O<SUB>3</SUB> substrates were discussed based on the detailed results of Scanning Electron Microscopy, Raman Spectrum and X-ray Diffraction Spectrum.
In this paper homogeneous and dense diamond films with good crystalline quality are successfully deposited on porous silicon surfaces by the microwave plasma assisted chemical vapor deposition method. Photoluminescence measurements show that the CVD diamond film-coated porous silicon has a weak shift of emission wavelength as compared with the stored porous silicon without a diamond film, and its PL intensity almost doesn't change with time. It means the diamond film can efficiently stabilize the PL wavelength and intensity of porous silicon and provide a better passivation effect. In addition, due to its well-known high hardness, the CVD diamond film can improve the mechanical strength of PS surface, and is therefore a promising candidate for passivation of porous silicon in the future.