MOSAIC GROWTH OF DIAMOND - A STUDY OF HOMOEPITAXIAL FLAME DEPOSITION AND ETCHING OF (001)-ORIENTED DIAMOND LAYERS

This study describes homoepitaxial growth and etch phenomena observed on cubic diamond faces as obtained by the application of an acetylene- oxygen combustion flame. It is demonstrated that flame etching of the diamond substrates prior to growth decreases the number of crystallogr aphic imperfections in the diamond layers especially at the edges. Thi s enables a more uniform distributed step generation by the large numb er of individual dislocations present in the used natural type IIa dia mond substrates. Due to this improvement it appears possible to grow o ne single crystal diamond layer on top of several closely spaced, well -aligned natural diamond substrates. In the present work the overgrowt h of a three-piece mosaic structure with gaps along [100] as well as a long [110] is reported for the first time. The single crystal nature o f this flame-deposited diamond layer could be confirmed by the observa tion of continuous growth step patterns at the surface across the join t regions. The widths of the gaps between the substrates in the origin al mosaic structure varied from 7 to 25 mu m, which is more than an or der of magnitude larger than the gaps along [100] in two-piece mosaic structures, of which the single crystal overgrowth by HFCVD was pervio usly reported. Comparison of micro-Raman spectra obtained from the joi nt regions with those from other parts of the overgrown mosaics discus sed in the present work, show a larger FWHM of the diamond peak in cas e of a [110] joint and a shift of the peak position to higher wave num bers in case of a [100] joint.