VAPOR-GROWN POLYCRYSTALLINE DIAMOND FILMS - MICROSCOPIC, MESOSCOPIC AND ATOMIC SURFACE-STRUCTURES

A detailed analysis with scanning electron and electron tunnelling mic roscopy of microscopic, mesoscopic and atomic surface structures as we ll as the growth forms of vapour grown polycrystalline diamond films i s presented. The growth form as a function of the substrate temperatur e T-S shifts from the octahedral shape at 990 K over the cube-octahedr al shape at similar to 1100 K to the cubic shape at 1275 K. The major change appears in a very narrow temperature range around 1100 K-only a n increase of T-S by 9% from 1050 to 1150 K is necessary to change the growth form from almost octahedral to cubic. Around this transition t emperature, the microscopic (100) structure changes with increasing T- S from smooth to rough and the mesoscopic (100) structure vice versa f rom rough to smooth. In addition, there is evidence that the atomic (1 00) structure changes from the hydrogenated to the non-hydrogenated 2 x 1 reconstruction. A possible explanation for all these findings is a change from ineffective to effective surface migration caused by a su rface transformation at similar to 1100 K. This explanation is strongl y supported by a diamond growth process described in the literature. F or the ill facets, a similar comprehensive surface structure character isation was not possible due to the pronounced 100 texture formation a t low T-S. On the microscopic scale, they appeared rough in either cas e. For T-S > 1050 K, mesoscopic images show triangular steps and islan ds. Regarding the atomic structures, at least three different structur es were found by scanning tunnelling microscopy: A hexagon, row and ri ng-like structure are attributed to atomic 1 x 1, 2 x 1, and 2 x 2 or (root 3 x root 3)R30 degrees structures. (C) 1998 Elsevier Science Ltd . All rights reserved.