Electron microscopic and interferometric studies of diamond crystals

Abstract

Early chapters review the structure and physical properties of diamond, the theories of crystal growth and dissolution and the methods for synthesizing diamond. Chapter 5 describes surface topographical studies on diamonds by previous workers and chapter 6 presents a survey of previous experiments on diamond e telling. Chapter 7 describes the techniques used and these include interferometry and electron microscopy. A single-stage replica technique developed during the present investigation for studying the surfaces of microcrystals only a few microns in size and a two-stage technique for crystals more than 100 microns in size are described in detail. The former was used for studying the surfaces of Du-Pont synthetic diamonds. De Beers synthetic diamonds are for the first time studied in detail. Electron microscopic studies reveal many new surface details. A notable change of orientation of etch pits on the cubic faces was discovered at about 600 to 650°C. To investigate this phenomenon, an etching apparatus was designed which agitated the specimen during etching. Results indicate that the by-products of the etching reaction at sites of fast etching are responsible for the change in etch-pit orientation. The change in etch-pit orientation was observed also on the cube faces of cubo-octahedral diamonds and on polished (100) faces which indicated that the phenomenon is probably an intrinsic property of all cubic faces. Detailed studies on the etching of naturally smooth cubic faces are here being reported for the first time. Optical and electron optical studies indicate that the cube faces of these cubo-octahedral crystals probably arise from a dissolution mechanism. Electron-microscopic studies on the natural cubic diamonds suggest that 'quadrons' are growth features. In addition, octahedral faces of the Premier Mine micro-diamonds are studied in detail. They show various features in addition to the usual ones. A mechanism for their formation is suggested.