Optical studies on surfaces of natural and synthetic cubic diamonds

The importance of diamond in modern technology, and crystal structure (with emphasis on diamond) are discussed. Theories of crystal growth are briefly reviewed. After describing previous work on the surface topography of diamond that of diamond of the cubic habit is described in detail for the first time. A brief review is given of etch studies on diamond surfaces. Etch figures obtained on natural cubic diamond surfaces and on polished sections of both cubic and octahedral diamonds are described. Two different types of etch pits were obtained on polished surfaces, and also observed on surfaces of synthetics, and the nature of these is discussed. Arrays of etch pits obtained on sections of cubes are described and related to the strain patterns. Etch patterns obtained on sections of octahedral reveal that the diamonds are made up of three dimensional layers of different character. Ultra-violet absorption studies show that these layers are of type I and type II material. We have estimated, from observed etch pit densities, the number of dislocations in type I material to be in excess of 4 x 10 per mm and in type II material as low as 6 x 10 per mm.;.Some evidence is given, drawing on our own observations of etch patterns and the work of others, to suggest that many diamonds may have grown around a central core. An attempt is made to explain the origin of etch pits on the natural faces and polished sections of cubic diamonds, and the parallel curved (convex and concave) layers within an octahedral diamond.